Effect of a dimer of nanoparticles on the linewidth of forbidden E2 transitions
Guzatov, D. V.; Klimov, V. V.
2016-07-01
In the framework of classical electrodynamics we have obtained and investigated analytical expressions for the radiation linewidth of forbidden E2 transitions in an atom located near a dimer of spherical particles. It is shown that the material of particles, their location and size have a significant effect on the linewidth of the E2 transition in the atom. It is found that in the gap between metal spherical nanoparticles, the linewidth of E2 transitions in the atom can take on substantially larger values than in the case of an atom near a single metal nanoparticle.
E1, M1, E2 transition energies and probabilities of W$^{54+}$ ions
Ding, Xiao-bin; Liu, Jia-xin; Koike, Fumihiro; Murakami, Izumi; Kato, Daiji; Sakaue, Hiroyuki A; Nakamura, Nobuyuki; Dong, Chen-zhong
2016-01-01
A comprehensive theoretical study of the E1, M1, E2 transitions of Ca-like tungsten ions is presented. Using multi-configuration Dirac-Fock (MCDF) method with a restricted active space treatment, the wavelengths and probabilities of the M1 and E2 transitions between the multiplets of the ground state configuration ([Ne]3s$^{2}$3p$^{6}$3d$^{2}$) and of the E1 transitions between [Ne]3s$^{2}$3p$^{5}$3d$^{3}$ and [Ne]3s$^{2}$3p$^{6}$3d$^{2}$ have been calculated. The results are in reasonable agreement with available experimental data. The present E1 and M1 calculations are compared with previous theoretical values. For E2 transitions, the importance of electron correlation from 3s and 3p orbitals is pointed out. Several strong E1 transitions are predicted, which have potential advantage for plasma diagnostics.
Effect of layered nanostructures on the linewidth of forbidden E2 transitions
Guzatov, D. V.; Klimov, V. V.
2017-08-01
In the framework of classical electrodynamics, analytical expressions are derived and investigated for the linewidth of forbidden E2 transitions in an atom (molecule) located near layered metal – dielectric nanostructures. It is shown that the radiation intensity at the forbidden transition during detection in the halfspace behind a layered nanostructure can significantly exceed the intensity during detection in the half-space where an atom (molecule) is located.
E2 transitions between excited single-phonon states: Role of ground-state correlations
Energy Technology Data Exchange (ETDEWEB)
Kamerdzhiev, S. P. [National Research Centre Kurchatov Institute (Russian Federation); Voitenkov, D. A., E-mail: dvoytenkov@ippe.ru [Institute for Physics and Power Engineering (Russian Federation)
2016-11-15
The probabilities for E2 transitions between low-lying excited 3{sup −} and 5{sup −} single-phonon states in the {sup 208}Pb and {sup 132}Sn magic nuclei are estimated on the basis of the theory of finite Fermi systems. The approach used involves a new type of ground-state correlations, that which originates from integration of three (rather than two, as in the random-phase approximation) single-particle Green’s functions. These correlations are shown to make a significant contribution to the probabilities for the aforementioned transitions.
Energy Technology Data Exchange (ETDEWEB)
Margetan, F.J.
1979-01-01
A closed expression is presented for intrinsic-coordinate (..beta.., ..gamma.., theta/sub i/) eigenfunctions of the hydrodynamic, quadrupole-vibration Hamiltonian of A. Bohr. These functions are used as an expansion basis for the treatment of more general collective Hamiltonians. Two classes of such Hamiltonians are considered. In each the potential energy term of the Bohr Hamiltonian, 1/2 C..beta../sup 2/, was replaced with a more general function of the shape coordinates, V(..beta.., ..gamma..). The potential of Gneuss and Greiner (1) is used to demonstrate the soundness of the calculational techniques, and to illustrate convergence properties of calculated energies. Potentials possessing a single minimum on 0 less than or equal to ..gamma.. less than or equal to 60/sup 0/ are considered through the study of a quadratic-potential (QP) Hamiltonian. The smooth development from spherical to asymmetrically deformed nuclear shapes is investigated by systematically varying the parameters ..beta../sub 0/ and C/sub ..gamma../. Model energies and E2 transition rates are traced during this process. The QP model is then applied to /sup 106/Pd, /sup 166/Er, /sup 182/W, /sup 122/Te, and /sup 186/ /sup 188/ /sup 190/ /sup 192/Os. Low-energy ..gamma.. vibrations appear to play a prominent role in the latter five nuclei, and the QP model offers a better accounting of experimental spectra than does the model of Davydov and Chaban (2). 74 references.
Rudigier, M; Dannhoff, M; Gerst, R-B; Jolie, J; Saed-Samii, N; Stegemann, S; Régis, J-M; Robledo, L M; Rodríguez-Guzmán, R; Blazhev, A; Fransen, Ch; Warr, N; Zell, K O
2015-01-01
The available data for E2 transition strengths in the region between neutron-deficient Hf and Pt isotopes are far from complete. More and precise data are needed to enhance the picture of structure evolution in this region and to test state-of-the-art nuclear models. In a simple model, the maximum collectivity is expected at the middle of the major shell. However, for actual nuclei, this picture may no longer be the case, and one should use a more realistic nuclear-structure model. We address this point by studying the spectroscopy of Hf. We remeasure the 2^+_1 half-lives of 172,174,176Hf, for which there is some disagreement in the literature. The main goal is to measure, for the first time, the half-lives of higher-lying states of the rotational band. The new results are compared to a theoretical calculation for absolute transition strengths. The half-lives were measured using \\gamma-\\gamma and conversion-electron-\\gamma delayed coincidences with the fast timing method. For the determination of half-lives i...
Generalized seniority and E 2 transitions in the tin isotopes
Morales, Irving O.; Van Isacker, P.; Talmi, I.
2011-09-01
Recently, a shallow minimum was discovered in B(E2) values in even Sn isotopes around the middle of the neutron major shell. A peak in that region was expected according to calculations using generalized seniority. In a model calculation we show that the observed shape is consistent with generalized seniority. It seems to be due to the order of filling of j-orbits.
Forbidden M1 and E2 transitions in monovalent atoms and ions
Safronova, U I; Johnson, W R
2016-01-01
We carried out a systematic high-precision relativistic study of the forbidden magnetic-dipole and electric-quadrupole transitions in Ca+, Rb, Sr+, Cs, Ba+, Fr, Ra+, Ac2+, and Th3+. This work is motivated by the importance of these transitions for tests of fundamental physics and precision measurements. The relative importance of the relativistic, correlation, Breit correction, and contributions of negative-energy states is investigated. Recommended values of reduced matrix elements are presented together with their uncertainties. The matrix elements and resulting lifetimes are compared with other theoretical values and with experiment where available.
E1M1 and E1E2 transition probabilities in one-electron ions
Energy Technology Data Exchange (ETDEWEB)
Labzowsky, L.N. [Institute of Physics, St. Petersburg State University, Uljanovskaya 1, Petrodvorets, 198904 St. Petersburg (Russian Federation) and Petersburg Nuclear Physics Institute, Gatchina, 188350 St. Petersburg (Russian Federation)]. E-mail: leonti@landau.phys.spbu.ru; Shonin, A.V. [Institute of Physics, St. Petersburg State University, Uljanovskaya 1, Petrodvorets, 198904 St. Petersburg (Russian Federation)
2004-12-06
The quantum electrodynamical (QED) theory of the two-photon transitions in hydrogenlike ions is presented. The emission probability for 2s1/2->2{gamma}(E1)+1s1/2 transitions is calculated and compared to the results of the previous calculations. The emission probabilities 2p1/2->{gamma}(E1)+{gamma}(E2)+1s1/2 and 2p1/2->{gamma}(E1)+{gamma}(M1)+1s1/2 are also calculated for the nuclear charge Z values 1=
E1M1 and E1E2 transition probabilities in one-electron ions
Labzowsky, L. N.; Shonin, A. V.
2004-12-01
The quantum electrodynamical (QED) theory of the two-photon transitions in hydrogenlike ions is presented. The emission probability for 2s→2γ(E1)+1s transitions is calculated and compared to the results of the previous calculations. The emission probabilities 2p→γ(E1)+γ(E2)+1s and 2p→γ(E1)+γ(M1)+1s are also calculated for the nuclear charge Z values 1⩽Z⩽100. This is the first calculation of the two latter probabilities. The results are given in two different gauges.
Enhanced $0_{g.s.}^+ \\to 2_1^+$ E2 Transition Strength in $^{112,114}$Sn
Kumar, R; Jhingan, A; Muralithar, S; Mukherjee, S; Reiter, P; Gorska, M; Bhowmik, R K; Cederkall, J; Siwal, D; Doornenbal, P; Garg, R; Appannababu, S; Kojouharov, I; Grawe, H; Singh, P P; Mandal, S; Sharma, A; Schaffner, H; Ekstrom, A; Caceres, L; Prokopowicz, W; Kaur, J; Gerl, J; Singh, R P; Bednarczyk, P
2011-01-01
The poorly known B(E2; 0(+) -> 2(+)) values of (112)Sn and (114)Sn have been measured to high precision. Two Coulomb excitation experiments were performed to determine the reduced transition probabilities relative to (116)Sn in order to minimize the systematic errors. The obtained B(E2 up arrow) values of 0.242(8) e(2)b(2) for (112)Sn and 0.232(8) e(2)b(2) for (114)Sn confirm the tendency of large B(E2 up arrow) values for the lighter tin isotopes below the midshell (116)Sn that has been observed recently in various radioactive ion beam experiments.
Pérez, E A Coello
2015-01-01
We present a model-independent approach to electric quadrupole transitions of deformed nuclei. Based on an effective theory for axially symmetric systems, the leading interactions with electromagnetic fields enter as minimal couplings to gauge potentials, while subleading corrections employ gauge-invariant non-minimal couplings. This approach yields transition operators that are consistent with the Hamiltonian, and the power counting of the effective theory provides us with theoretical uncertainty estimates. We successfully test the effective theory in homonuclear molecules that exhibit a large separation of scales. For ground-state band transitions of rotational nuclei, the effective theory describes data well within theoretical uncertainties at leading order. In order to probe the theory at subleading order, data with higher precision would be valuable. For transitional nuclei, next-to-leading order calculations and the high-precision data are consistent within the theoretical uncertainty estimates. We also...
Institute of Scientific and Technical Information of China (English)
万建杰; 颉录有; 董晨钟; 蒋军; 颜君
2007-01-01
利用基于全相对论框架下的多组态Dirac-Fock理论方法发展起来的程序包GRASP92和新发展的处理辐射跃迁过程的程序REOS99,计算了类镍等电子系列离子(Z=45-95)的基组态3s23p63d10 1S0以及低激发组态3s23p63d94l,3s23p53d104l和3s3p63d104 l(l=s,p,d,f)的能级及其向基态的M1,M2,E2禁戒跃迁概率.通过分析高离化类镍离子在特定的原子序数范围内由于存在能级交叉而产生的强组态相互作用,解释了高离化类镍离子禁戒跃迁概率的反常变化现象,探讨了禁戒跃迁概率受强组态相互作用影响而变化的一般规律.
Search for Fingerprints of Tetrahedral Symmetry in $^{156}Gd$
Doan, Q T; Stezowski, O; Dudek, J; Mazurek, K; Gózdz, A; Piot, J; Duchêne, G; Gall, B; Molique, H; Richet, M; Medina, P; Guinet, D; Redon, N; Schmitt, C; Jones, P; Julin, R; Peura, P; Ketelhut, S; Nyman, M; Jakobsson, U; Maj, A; Zuber, K; Bednarczyk, P; Schunck, N; Dobaczewski, J; Astier, A; Deloncle, I; Verney, D; De Angelis, G; Gerl, J
2008-01-01
Theoretical predictions suggest the presence of tetrahedral symmetry as an explanation for the vanishing intra-band E2-transitions at the bottom of the odd-spin negative parity band in $^{156}Gd$. The present study reports on experiment performed to address this phenomenon. It allowed to determine the intra-band E2 transitions and branching ratios B(E2)/B(E1) of two of the negative-parity bands in $^{156}Gd$.
W(5): Wobbling Mode in the Framework of the X(5) Model
Bonatsos, D; Petrellis, D; Terziev, P A; Bonatsos, Dennis
2004-01-01
Using in the Bohr Hamiltonian the approximations leading to the Bohr and Mottelson description of wobbling motion in even nuclei, a W(5) model for wobbling bands, coexisting with a X(5) ground state band, is obtained. Separation of variables is achieved by assuming that the relevant potential has a sharp minimum at gamma_0, which is the only parameter entering in the spectra and B(E2) transition rates (up to overall scale factors). B(E2) transition rates exhibit the features expected in the wobbling case, while the spectrum for gamma_0=20 degrees is in good agreement with experimental data for Dy-156.
Electric Characteristics of Rotational States positive parity in isotopes 170,172,174Yb
Usmanov, P N; Kassim, H Abu; Salikhbaev, U S
2015-01-01
Accounting for Coriolis mixing of experimentally known rotational bands with $K^{\\pi}< 3^+$, non-adiabatic effects in energy and electric characteristics of excited states are investigated, within phenomenological model. The energy and wave function structure of excited states are calculated. The finding reveals that the bands mixing has been found to have considerable impact on the wave function of low-lying states $0^+$ and $2^+$ bands. In addition, the probabilities of $E2$-- transitions have been calculated. The values from calculations of $B(E2)$-- transitions from $0_2^+$, $0_3^+$, $2_1^+$, and $2_2^+$ bands are compared with the experimental data.
Search for Fingerprints of Tetrahedral Symmetry in ^{156}Gd
Energy Technology Data Exchange (ETDEWEB)
Doan, Q. T. [Universite Lyon 1, Villeurbanne, France; Curien, D. [CNRS, Strasbourg, France; Stezowski, O. [Universite Lyon 1, Villeurbanne, France; Dudek, J. [CNRS, Strasbourg, France; Mazurek, K. [H. Niewodniczanski Institute of Nuclear Physics (INP), Krakow, Poland; Gozdz, A. [Maria Curie-Sklodowskiej, Lublin, Poland; Piot, J. [CNRS, Strasbourg, France; Duchene, G. [CNRS, Strasbourg, France; Gall, B. [CNRS, Strasbourg, France; Molique, H. [CNRS, Strasbourg, France; Richet, M. [CNRS, Strasbourg, France; Guinet, D. [Universite Lyon 1, Villeurbanne, France; Redon, N. [Universite Lyon 1, Villeurbanne, France; Schmitt, Ch. [Universite Lyon 1, Villeurbanne, France; Jones, P. [University of Jyvaskyla; Peura, P. [University of Jyvaskyla; Ketelhut, S. [University of Jyvaskyla; Nyman, M. [University of Jyvaskyla; Jakobsson, U. [University of Jyvaskyla; Greenlees, P. T. [University of Jyvaskyla; Julin, R. [University of Jyvaskyla; Juutinen, S. [University of Jyvaskyla; Rahkila, P. [University of Jyvaskyla; Maj, A. [H. Niewodniczanski Institute of Nuclear Physics (INP), Krakow, Poland; Zuber, K. [H. Niewodniczanski Institute of Nuclear Physics (INP), Krakow, Poland; Bednarczyk, P. [H. Niewodniczanski Institute of Nuclear Physics (INP), Krakow, Poland; Schunck, N. [Oak Ridge National Laboratory (ORNL); Dobaczewski, J. [Warsaw University; Astier, A. [CNRS, Orsay, France; Deloncle, I. [CNRS, Orsay, France; Verney, D. [CNRS/IN2P3, Orsay, France; De Angelis, G. [INFN, Laboratori Nazionali di Legnaro, Italy; Gerl, J. [Gesellschaft fur Schwerionenforschung (GSI), Germany
2009-01-01
Theoretical predictions suggest the presence of tetrahedral symmetry as an explanation for the vanishing intra-band E2 transitions at the bottom of the odd-spin negative-parity band in ^{156}Gd. The present study reports on experiment performed to address this phenomenon. It allowed to remove certain ambiguities related to the intra-band E2 transitions in the negative-parity bands to determine the new inter-band transitions and reduced probability ratios B(E2)/B(E1) and, for the first time, to determine the experimental uncertainties related to the latter observable.
Inelastic scattering of {sup 9}Li and excitation mechanism of its first excited state
Energy Technology Data Exchange (ETDEWEB)
Al Falou, H. [Astronomy and Physics Department, Saint Mary' s University, Halifax, Nova Scotia B3H 3C3 (Canada); TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Kanungo, R., E-mail: ritu@triumf.ca [Astronomy and Physics Department, Saint Mary' s University, Halifax, Nova Scotia B3H 3C3 (Canada); Andreoiu, C.; Cross, D.S. [Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Davids, B.; Djongolov, M. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Gallant, A.T. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Department of Physics, University of British Columbia, British Columbia V6T 1Z4 (Canada); Galinski, N.; Howell, D. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Kshetri, R.; Niamir, D. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Orce, J.N. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Department of Physics, University of the Western Cape, P/B X17, Bellville, ZA-7535 (South Africa); Shotter, A.C. [Department of Physics and Astronomy, University of Edinburgh, Edinburgh (United Kingdom); Sjue, S. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Tanihata, I. [Research Center for Nuclear Physics, Osaka University, Mihogaoka, Ibaraki, Osaka 567 0047 (Japan); Thompson, I.J. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Triambak, S. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Uchida, M. [Astronomy and Physics Department, Saint Mary' s University, Halifax, Nova Scotia B3H 3C3 (Canada); Walden, P. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Wiringa, R.B. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States)
2013-04-25
The first measurement of inelastic scattering of {sup 9}Li from deuterons at the ISAC facility is reported. The measured angular distribution for the first excited state confirms the nature of excitation to be an E2 transition. The quadrupole deformation parameter is extracted from an analysis of the angular distribution.
Empirical Example of Nucleus with Transitional Dynamical Symmetry X(5)
Institute of Scientific and Technical Information of China (English)
张大立; 赵惠英
2002-01-01
By analysing the energy spectrum, E2 transition rates and branching ratios, it is shown explicitly that the nucleus 150Nd provides an empirical example with X(5) symmetry at the critical point of the transition from U(5) to SU(3) symmetry.
Evidence for a Smooth Onset of Deformation in the Neutron-Rich Kr Isotopes
Albers, M.; Warr, N.; Nomura, K.; Blazhev, A.; Jolie, J.; Muecher, D.; Bastin, B.; Bauer, C.; Bernards, C.; Bettermann, L.; Bildstein, V.; Butterworth, J.; Cappellazzo, M.; Cederkaell, J.; Cline, D.; Darby, I.; Das Gupta, S.; Daugas, J. M.; Davinson, T.; De Witte, H.; Diriken, J.; Filipescu, D.; Fiori, E.; Fransen, C.; Gaffney, L. P.; Georgiev, G.; Gernhaeuser, R.; Hackstein, M.; Heinze, S.; Hess, H.; Huyse, M.; Jenkins, D.; Konki, J.; Kowalczyk, M.; Kroell, T.; Kruecken, R.; Litzinger, J.; Lutter, R.; Marginean, N.; Mihai, C.; Moschner, K.; Napiorkowski, P.; Singh, B. S. Nara; Nowak, K.; Otsuka, T.; Pakarinen, J.; Pfeiffer, M.; Radeck, D.; Reiter, P.; Rigby, S.; Robledo, L. M.; Rodriguez-Guzman, R.; Rudigier, M.; Sarriguren, P.; Scheck, M.; Seidlitz, M.; Siebeck, B.; Simpson, G.; Thoele, P.; Thomas, T.; Van de Walle, J.; Van Duppen, P.; Vermeulen, M.; Voulot, D.; Wadsworth, R.; Wenander, F.; Wimmer, K.; Zell, K. O.; Zielinska, M.
2012-01-01
The neutron-rich nuclei Kr-94,Kr-96 were studied via projectile Coulomb excitation at the REX-ISOLDE facility at CERN. Level energies of the first excited 2(+) states and their absolute E2 transition strengths to the ground state are determined and discussed in the context of the E(2(1)(+)) and
The Microscopic Approach of sdgIBM-1 and Its Application to Nucleus 154Gd
Institute of Scientific and Technical Information of China (English)
Liu Yong
2003-01-01
Based on the Dyson expansion theory, a microscopic approach of sdgIBM-1 is presented and applied to nucleus 154Gd in this paper. The energy spectra and E2 transition have been calculated. Good agreement is obtained in comparison with experimental results.
Analyses of β-Bands of 230,232Th and 232,234U by the Projected Shell Model
Institute of Scientific and Technical Information of China (English)
CUI Ji-Wei; ZHOU Xian-Rong; CHEN Fang-Qi; SUN Yang; WU Cheng-Li
2012-01-01
The ground bands and β-bands of four nuclei 230,232Th and 232,234U in the actinide region are investigated by introducing a collective Do pair into the projected shell model.We discuss the collectivity of the Do pair.The calculated energy schemes agree well with experimental data,and so do the E2 transition rates.%The ground bands and β-bands of four nuclei 230,232 Th and 232,234 U in the actinide region are investigated by-introducing a collective Do pair into the projected shell model. We discuss the collectivity of the D0 pair. The calculated energy schemes agree well with experimental data, and so do the E2 transition rates.
Effects of E2 and E1-E2 Interference on Coulomb Dissociation of 19C
Institute of Scientific and Technical Information of China (English)
Rajesh Kharab; Pardeep Singh; Ravinder Kumar
2007-01-01
We investigate the effects of higher order multipole transitions, in particular electric quadrupole (E2) and E1-E2interference, on the Coulomb dissociation of 19 C within the framework of the first order eikonal approximation.The sensitivity of the total Coulomb breakup cross section and the longitudinal momentum distribution of the core fragment to these effects are checked. The breakup occurs predominately through the dipole transition and the contribution of E2 transition to the total cross section is found to be within the range from 1 to 3% of that of E1. It is further observed that the E1-E2 interference term contributes nothing to the integrated cross section.On the other hand, the longitudinal momentum distribution is observed to be insensitive to the E2 transition while the E1-E2 interference introduces a small asymmetry in its shape.
Energy Technology Data Exchange (ETDEWEB)
Bonatsos, Dennis [Institute of Nuclear Physics, NCSR ' Demokritos' GR-15310 Aghia Paraskevi, Attiki (Greece)]. E-mail: bonat@inp.demokritos.gr; Lenis, D. [Institute of Nuclear Physics, NCSR ' Demokritos' GR-15310 Aghia Paraskevi, Attiki (Greece)]. E-mail: lenis@inp.demokritos.gr; Petrellis, D. [Institute of Nuclear Physics, NCSR ' Demokritos' GR-15310 Aghia Paraskevi, Attiki (Greece)]. E-mail: petrellis@inp.demokritos.gr; Terziev, P.A. [Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72 Tzarigrad Road, BG-1784 Sofia (Bulgaria)]. E-mail: terziev@inrne.bas.bg; Yigitoglu, I. [Institute of Nuclear Physics, NCSR ' Demokritos' GR-15310 Aghia Paraskevi, Attiki (Greece) and Hasan Ali Yucel Faculty of Education, Istanbul University, TR-34470 Beyazit, Istanbul (Turkey)]. E-mail: yigitoglu@istanbul.edu.tr
2005-08-11
A {gamma}-rigid solution of the Bohr Hamiltonian for {gamma}=30 deg. is derived, its ground state band being related to the second order Casimir operator of the Euclidean algebra E(4). Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are in close agreement to the E(5) critical point symmetry, as well as to experimental data in the Xe region around A=130.
Bonatsos, D; Petrellis, D; Terziev, P A; Yigitoglu, I; Bonatsos, Dennis
2005-01-01
A gamma-rigid solution of the Bohr Hamiltonian for gamma = 30 degrees is derived, its ground state band being related to the second order Casimir operator of the Euclidean algebra E(4). Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are in close agreement to the E(5) critical point symmetry, as well as to experimental data in the Xe region around A=130.
Transverse Wobbling in $^{135}$Pr
Matta, J T; Li, W; Frauendorf, S; Ayangeakaa, A D; Patel, D; Schlax, K W; Palit, R; Saha, S; Sethi, J; Trivedi, T; Ghugre, S S; Raut, R; Sinha, A K; Janssens, R V F; Zhu, S; Carpenter, M P; Lauritsen, T; Seweryniak, D; Chiara, C J; Kondev, F G; Hartley, D J; Petrache, C M; Mukhopadhyay, S; Lakshmi, D Vijaya; Raju, M Kumar; Rao, P V Madhusudhana; Tandel, S K; Ray, S; Dönau, F
2015-01-01
A pair of transverse wobbling bands has been observed in the nucleus $^{135}$Pr. The wobbling is characterized by $\\Delta I$ =1, E2 transitions between the bands, and a decrease in the wobbling energy confirms its transverse nature. Additionally, a transition from transverse wobbling to a three-quasiparticle band comprised of strong magnetic dipole transitions is observed. These observations conform well to results from calculations with the Tilted Axis Cranking (TAC) model and the Quasiparticle Triaxial Rotor (QTR) Model.
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
We study systematically the evolutive behaviors of some energy ratios,E2 transition rate ratios and isomer shift in the nuclear shape phase transitions.We find that the quantities sensitive to the phase transition and independent of free parameter(s) are approximately particle number N scale invariant around the critical point of the first order phase transition,similar to that in the second order phase transition.
Institute of Scientific and Technical Information of China (English)
ZHANG Yu; HOU ZhanFeng; LIU YuXin
2009-01-01
We study systematically the evolutive behaviors of some energy ratios,E2 transition rate ratios and Isomer shift in the nuclear shape phase transitions.We find that the quantities sensitive to the phase transition and independent of free parameter(s) are approximately particle number N scale invariant around the critical point of the first order phase transition,similar to that in the second order phase transition.
Description of 114Cd in the E(5) Symmetry
Institute of Scientific and Technical Information of China (English)
张进富; 龙桂鲁; 孙扬; 朱胜江; 刘凤英; 贾颖
2003-01-01
By analysing the known low-lying levels and the E2 transition rates, it is shown that the empirical scheme of 114Cd is in good overall agreement with the predictions of the transitional dynamical symmetry E(5) proposed by Iachello [Phys. Rev. Lett. 85 (2000) 3580]. This suggests that 114Cd may be better described by an E(5)nucleus than a U(5) nucleus as known before.
Extended IBA consistent-Q formalism applied to Ru and Pd isotopes
Energy Technology Data Exchange (ETDEWEB)
Bucurescu, D.; Cata, G.; Cutoiu, D.; Constantinescu, G.; Ivascu, M.; Zamfir, N.V.
1986-08-01
A consistent-Q formalism extended to an IBA-1 hamiltonian applicable also in the U(5) limit, is applied to Ru and Pd isotopes with N around 60. A good description of energy levels and E2 transition in these nuclei is obtained. The model is able to reproduce the main features of this transitional region, characterized by both rigid triaxial deformation and ..gamma..-softness.
Inter-band coincidences in the superdeformed well of {sup 190}Hg from gammasphere
Energy Technology Data Exchange (ETDEWEB)
Crowell, B.; Carpenter, M.P.; Janssens, R.V.F. [and others
1995-08-01
Very few experimental observables are ordinarily accessible for superdeformed (SD) states in the A {approximately} 150 and A {approximately} 190 regions. The gamma-decay out of the superdeformed bands usually proceeds directly to the normally deformed states, through highly fragmented pathways, making it difficult to determine the spins, parities and excitation energies of the SD states. The in-band E2 transitions are so collective (2 x 10{sup 3} single-particle units in the A {approximately} 190 region) that it is typically impossible to detect any of the competing M1 and E1 transitions between states in the SD well.
Microscopic study of low-lying yrast spectra in 100-108Mo isotopes
Indian Academy of Sciences (India)
Neeru Sawhney; Arun Bharti; S K Khosa
2002-10-01
Variation-after-projection (VAP) calculations in conjunction with Hartree–Bogoliubov (HB) ansatz have been carried out for = 100-108 molybdenum (Mo) isotopes. In this framework, the yrast spectra with $J^{}_{\\max}$ ≥ 10+, $B(E2)$ transition probabilities, quadrupole (2) and hexadecapole (4) deformation parameters, moment of inertia () and square of cranking frequency (2) for even–even Mo isotopes have been obtained. The results of the calculation give an indication that it is important to include the hexadecapole–hexadecapole component of the two-body interaction for obtaining various nuclear structure quantities in these Mo isotopes.
The Half Life of the 53 keV Level in {sup 197}Pt
Energy Technology Data Exchange (ETDEWEB)
Malmskog, S.G.
1967-02-15
The half life of the recently proposed 53 keV level in {sup 197}Pt has been measured to 18.5 {+-} 1.5 nsec using the delayed coincidence technique. This level, which is identified with the f{sub 5/2} single particle state, decays directly to the p{sub 1/2} ground state in {sup 197}Pt. The reduced E2 transition probability for this 53 keV transition has been deduced and compared with the results obtained for the corresponding transitions in other Pt, Hg, and Pb isotopes and with the theoretical predictions by Sorensen and by Wahlborn and Martinson.
Z(5): critical point symmetry for the prolate to oblate nuclear shape phase transition
Energy Technology Data Exchange (ETDEWEB)
Bonatsos, Dennis; Lenis, D.; Petrellis, D.; Terziev, P.A
2004-05-27
A critical point symmetry for the prolate to oblate shape phase transition is introduced, starting from the Bohr Hamiltonian and approximately separating variables for {gamma}=30 deg. Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are found to be in good agreement with experimental data for {sup 194}Pt, which is supposed to be located very close to the prolate to oblate critical point, as well as for its neighbours ({sup 192}Pt, {sup 196}Pt)
Z(5): Critical point symmetry for the prolate to oblate nuclear shape phase transition
Bonatsos, D; Petrellis, D; Terziev, P A; Bonatsos, Dennis
2004-01-01
A critical point symmetry for the prolate to oblate shape phase transition is introduced, starting from the Bohr Hamiltonian and approximately separating variables for $\\gamma=30^{\\rm o}$. Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are found to be in good agreement with experimental data for 194-Pt, which is supposed to be located very close to the prolate to oblate critical point, as well as for its neighbours (192-Pt, 196-Pt).
X(3): An Exactly Separable Gamma-Rigid Version of the X(5) Critical Point Symmetry
Bonatsos, D; Petrellis, D; Terziev, P A; Yigitoglu, I; Bonatsos, Dennis
2006-01-01
A gamma-rigid version (with gamma=0) of the X(5) critical point symmetry is constructed. The model, to be called X(3) since it is proved to contain three degrees of freedom, utilizes an infinite well potential, is based on exact separation of variables, and leads to parameter free (up to overall scale factors) predictions for spectra and B(E2) transition rates, which are in good agreement with existing experimental data for 172-Os and 186-Pt. An unexpected similarity of the first beta bands of the X(5) nuclei 150-Nd, 152-Sm, 154-Gd, and 156-Dy to the X(3) predictions is observed.
Effective field theory for deformed atomic nuclei
Papenbrock, T.; Weidenmüller, H. A.
2016-05-01
We present an effective field theory (EFT) for a model-independent description of deformed atomic nuclei. In leading order this approach recovers the well-known results from the collective model by Bohr and Mottelson. When higher-order corrections are computed, the EFT accounts for finer details such as the variation of the moment of inertia with the band head and the small magnitudes of interband E2 transitions. For rotational bands with a finite spin of the band head, the EFT is equivalent to the theory of a charged particle on the sphere subject to a magnetic monopole field.
Electric quadrupole transitions of the Bohr Hamiltonian with Manning-Rosen potential
Chabab, M.; El Batoul, A.; Lahbas, A.; Oulne, M.
2016-09-01
Analytical expressions of the wave functions are derived for a Bohr Hamiltonian with the Manning-Rosen potential in the cases of γ-unstable nuclei and axially symmetric prolate deformed ones with γ ≈ 0. By exploiting the results we have obtained in a recent work on the same theme Ref. [1], we have calculated the B (E 2) transition rates for 34 γ-unstable and 38 rotational nuclei and compared to experimental data, revealing a qualitative agreement with the experiment and phase transitions within the ground state band and showing also that the Manning-Rosen potential is more appropriate for such calculations than other potentials.
Effects of proton angular momentum alignment on the two-shears-like mechanism in $^{101}$Pd
Zhang, Zhen-Hua
2016-01-01
The recently observed possible antimagnetic rotation band in $^{101}$Pd is investigated by the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the blocking effects are taken into account exactly. The experimental moments of inertia and reduced $B(E2)$ transition probabilities and their variations with the rotational frequency $\\omega$ are well reproduced. By analyzing the $\\omega$-dependence of the occupation probability of each cranked Nilsson orbital near the Fermi surface and the contributions of valence orbitals in each major shell to the total angular momentum alignment, the upbending mechanism of $\
Electric quadrupole transitions of the Bohr Hamiltonian with Manning-Rosen potential
Chabab, M; Lahbas, A; Oulne, M
2016-01-01
Analytical expressions of the wave functions are derived for a Bohr Hamiltonian with the Manning{Rosen potential in the cases of {\\gamma}-unstable nuclei and axially symmetric prolate deformed ones with {\\gamma}=0. By exploiting the results we have obtained in a recent work on the same theme Ref. [1], we have calculated the B(E2) transition rates for 34 {\\gamma}-unstable and 38 rotational nuclei and compared to experimental data, revealing a qualitative agreement with the experiment and phase transitions within the ground state band and showing also that the Manning-Rosen potential is more appropriate for such calculations than other potentials.
Effective field theory for deformed atomic nuclei
Papenbrock, T
2015-01-01
We present an effective field theory (EFT) for a model-independent description of deformed atomic nuclei. In leading order this approach recovers the well-known results from the collective model by Bohr and Mottelson. When higher-order corrections are computed, the EFT accounts for finer details such as the variation of the moment of inertia with the band head and the small magnitudes of interband $E2$ transitions. For rotational bands with a finite spin of the band head, the EFT is equivalent to the theory of a charged particle on the sphere subject to a magnetic monopole field.
Bohr Hamiltonian with Hulthen plus ring-shaped potential for triaxial nuclei
Energy Technology Data Exchange (ETDEWEB)
Chabab, M.; Lahbas, A.; Oulne, M. [Cadi Ayyad University, High Energy Physics and Astrophysics Laboratory, Department of Physics, Faculty of Sciences Semlalia, P. O. B. 2390, Marrakesh (Morocco)
2015-10-15
In this paper, we solve the eigenvalues and eigenvectors problem with the Bohr collective Hamiltonian for triaxial nuclei. The β-part of the collective potential is taken to be equal to the Hulthen potential while the γ-part is defined by a new generalized potential obtained from a ring-shaped one. Analytical expressions for spectra and wave functions are derived by means of a recent version of the asymptotic iteration method and the usual approximations. The calculated energies and B(E2) transition rates are compared with experimental data and the available theoretical results in the literature. (orig.)
Bohr Hamiltonian with Hulth?en plus Ring shaped potential for triaxial nuclei
Chabab, M; Oulne, M
2015-01-01
In this paper, we solve the eigenvalues and eigenvectors problem with Bohr collective Hamil- tonian for triaxial nuclei. The ? beta part of the collective potential is taken to be equal to Hulth?en potential while the gamma part is de?ned by a new generalized potential obtained from a ring shaped one. Analytical expressions for spectra and wave functions are derived by means of a recent version of the asymptotic iteration method and the usual approximations. The calculated energies and B(E2) transition rates are compared with experimental data and the available theoretical results in the literature.
High-spin states in boson models with applications to actinide nuclei
Kuyucak, S
1995-01-01
We use the 1/N expansion formalism in a systematic study of high-spin states in the sd and sdg boson models with emphasis on spin dependence of moment of inertia and E2 transitions. The results are applied to the high-spin states in the actinide nuclei ^{232}Th, ^{234-238}U, where the need for g bosons is especially acute but until now, no realistic calculation existed. We find that the d-boson energy plays a crucial role in description of the high-spin data.
DSAM lifetime measurements for the chiral pair in {sup 194}Tl
Energy Technology Data Exchange (ETDEWEB)
Masiteng, P.L.; Bvumbi, S.P. [National Research Foundation, iThemba LABS, PO Box 722, Somerset West (South Africa); University of the Western Cape, Private Bag X17, Bellville (South Africa); University of Johannesburg, PO Box 524, Auckland Park (South Africa); Pasternak, A.A. [A.F. Ioffe Physical-Technical Institute, St.-Petersburg (Russian Federation); Lawrie, E.A.; Shirinda, O.; Lawrie, J.J.; Bark, R.A.; Kheswa, N.Y.; Lieder, E.O.; Lieder, R.M.; Mullins, S.M.; Murray, S.H.T. [National Research Foundation, iThemba LABS, PO Box 722, Somerset West (South Africa); Lindsay, R. [University of the Western Cape, Private Bag X17, Bellville (South Africa); Madiba, T.E.; Sharpey-Schafer, J.F. [National Research Foundation, iThemba LABS, PO Box 722, Somerset West (South Africa); University of the Western Cape, Private Bag X17, Bellville (South Africa); Ndayishimye, J.; Papka, P. [National Research Foundation, iThemba LABS, PO Box 722, Somerset West (South Africa); University of Stellenbosch, Department of Physics, Private Bag X1, Matieland (South Africa); Ntshangase, S.S. [National Research Foundation, iThemba LABS, PO Box 722, Somerset West (South Africa); University of Cape Town, Department of Physics, Private Bag, Rondebosch (South Africa)
2016-02-15
Most important for the identification of chiral symmetry in atomic nuclei is to establish a pair of bands that are near-degenerate in energy, but also in B(M1) and B(E2) transition probabilities. Dedicated lifetime measurements were performed for four bands of {sup 194}Tl, including the pair of four-quasiparticle chiral bands with close near-degeneracy, considered as a prime candidate for best chiral symmetry pair. The lifetime measurements confirm the excellent near-degeneracy in this pair and indicate that a third band may be involved in the chiral symmetry scenario. (orig.)
Quadrupole Collectivity beyond N=28: Intermediate-Energy Coulomb Excitation of Ar47,48
Winkler, R.; Gade, A.; Baugher, T.; Bazin, D.; Brown, B. A.; Glasmacher, T.; Grinyer, G. F.; Meharchand, R.; McDaniel, S.; Ratkiewicz, A.; Weisshaar, D.
2012-05-01
We report on the first experimental study of quadrupole collectivity in the very neutron-rich nuclei Ar47,48 using intermediate-energy Coulomb excitation. These nuclei are located along the path from doubly magic Ca to collective S and Si isotopes, a critical region of shell evolution and structural change. The deduced B(E2) transition strengths are confronted with large-scale shell-model calculations in the sdpf shell using the state-of-the-art SDPF-Uand EPQQM effective interactions. The comparison between experiment and theory indicates that a shell-model description of Ar isotopes around N=28 remains a challenge.
Forbidden transitions in a magneto-optical trap.
Bhattacharya, M; Haimberger, C; Bigelow, N P
2003-11-21
We report the first observation of a nondipole transition in an ultracold atomic vapor. We excite the 3P-4P electric quadrupole (E2) transition in 23Na confined in a magneto-optical trap, and we demonstrate its application to high-resolution spectroscopy by making the first measurement of the hyperfine structure of the 4P(1/2) level and extracting the magnetic dipole constant A=30.6+/-0.1 MHz. We use cw optical-optical double resonance accompanied by photoionization to probe the transition.
Generator coordinate method and superdeformation in A=190 nuclei
Dancer, H; Bonche, P; Flocard, H; Heenen, P H; Meyer, J; Meyer, M
1999-01-01
The Generator Coordinate Method with particle number projection using a set of Hartree-Fock plus BCS states is applied to the superdeformed even-even Hg and Pb isotopes. The q sub 3 sub 0 and q sub 3 sub 2 octupole vibrations are investigated in even-even Hg and Pb isotopes. These one-dimensional calculations predict that the collective octupole K suppi=0 sup - excitations are the lowest mode in energy. The electric monopole E0 decay out of superdeformed states is also compared to the electric quadrupole E2 transition rates.
Generator coordinate method and superdeformation in A=190 nuclei
Energy Technology Data Exchange (ETDEWEB)
Dancer, H.; Perres, S.; Bonche, P.; Flocard, H.; Heenen, P.-H.; Meyer, J. E-mail: jmeyer@ipnl.in2p3.fr; Meyer, M
1999-07-26
The Generator Coordinate Method with particle number projection using a set of Hartree-Fock plus BCS states is applied to the superdeformed even-even Hg and Pb isotopes. The q{sub 30} and q{sub 32} octupole vibrations are investigated in even-even Hg and Pb isotopes. These one-dimensional calculations predict that the collective octupole K{sup {pi}}=0{sup -} excitations are the lowest mode in energy. The electric monopole E0 decay out of superdeformed states is also compared to the electric quadrupole E2 transition rates.
Jungclaus, A.; Walker, J.; Leske, J.; Speidel, K.-H.; Stuchbery, A. E.; East, M.; Boutachkov, P.; Cederkäll, J.; Doornenbal, P.; Egido, J. L.; Ekström, A.; Gerl, J.; Gernhäuser, R.; Goel, N.; Górska, M.; Kojouharov, I.; Maier-Komor, P.; Modamio, V.; Naqvi, F.; Pietralla, N.; Pietri, S.; Prokopowicz, W.; Schaffner, H.; Schwengner, R.; Wollersheim, H.-J.
2011-09-01
Precise measurements of lifetimes in the picosecond range of excited states in the stable even-A Sn isotopes 112,114,116,122Sn have been performed using the Doppler shift attenuation technique. For the first excited 2+ states in 112Sn, 114Sn and 116Sn the E2 transition strengths deduced from the measured lifetimes are in disagreement with the previously adopted values. They indicate a shallow minimum at N = 66 in contrast to the maximum at mid-shell predicted by modern shell model calculations.
Measurement of the radiative branching ratio for the Hoyle state using cascade gamma decays
Directory of Open Access Journals (Sweden)
Alshahrani B.
2013-12-01
Full Text Available A new setup consisting of four 5” by 5” NaI scintillators and an array of particle detectors is being developed. Proton-gamma-gamma coincidences will be measured using the 12C(p, p′12C reaction at 10.5 MeV energy. The new setup will be used for the measurement of the electromagnetic decay rate of the Hoyle state via two E2 transitions. We report the initial experimental results for singles gamma and gamma-proton coincidences through inelastic scattering of protons on a 12C target.
Wu, Xin-Yi; Ghorui, S. K.; Wang, Long-Jun; Kaneko, K.; Sun, Yang
2017-01-01
We analyze the high-spin structure of the even-even 72-80Kr isotopes using the Projected Shell Model (PSM). With the help of the Pfaffian formulas, we have vigorously extended the quasi-particle (qp) basis of the PSM code and applied in this mass region for the first time. We consider a sufficiently large multi-qp configuration space in order to describe high-spin rotational behavior. The results show that the calculation can reproduce most of the known rotational bands with positive- or negative-parity. Moreover, some side bands appearing in the near-yrast region are predicted. The main structure for each band is discussed in terms of multi-qp configurations. The variations in moment of inertia with spin are explained in terms of successive band crossings among the 2-qp, 4-qp, 6-qp, and 8-qp states. The B (E 2) transition probabilities in these bands are also calculated. To further understand the high-spin behavior of these neutron-deficient nuclei and to confirm predictions of the present work, good high-spin data, especially for B (E 2) transitions, are called for.
Correspondence between phenomenological and IBM-1 models of even isotopes of Yb
A. Okhunov, A.; I. Sharrad, F.; Anwer, A. Al-Sammarraie; U. Khandaker, M.
2015-08-01
Energy levels and the reduced probability of E2- transitions for ytterbium isotopes with proton number Z = 70 and neutron numbers between 100 and 106 have been calculated through phenomenological (PhM) and interacting boson (IBM-1) models. The predicted low-lying levels (energies, spins and parities) and the reduced probability for E2- transitions results are reasonably consistent with the available experimental data. The predicted low-lying levels (gr-, β1- and γ1- band) produced in the PhM are in good agreement with the experimental data compared with those by IBM-1 for all nuclei of interest. In addition, the phenomenological model was successful in predicting the β2-, β3-, β4-, γ2- and 1+ - band while it was a failure with IBM-1. Also, the 3+- band is predicted by the IBM-1 model for 172Yb and 174Yb nuclei. All calculations are compared with the available experimental data. Supported by Fundamental Research Grant Scheme (FRGS) of Ministry of Higher Education of Malaysia (FRGS13-074-0315), Islamic Development Bank (IDB) (36/11201905/35/IRQ/D31, 37/IRQ/P30)
On the transition rates of the Fe X and Fe XIV corona lines
Energy Technology Data Exchange (ETDEWEB)
Trabert, E
2003-11-20
Despite a considerable scatter of the theoretical predictions of the M1/E2 transition rate of the ''red iron line'' (FeX) in the solar corona, there is disagreement of all the results with the single measurement that used an electrostatic ion trap. Employing a heavy-ion storage ring for measuring the same transition in isoelectronic ions of Co, Ni, and Cu, the situation has been clarified, and a new data point for FeX can be determined by extrapolation. This result agrees with the basic atomic structure prediction for the line strength in combination with the experimental transition energy. For the ''green iron line'' (FeXIV), a recent measurement with an electron beam ion trap has resolved similar discrepancies.
Shape vibrations and quasiparticle excitations in the lowest 0+ excited state of the Erbium isotopes
Chen, Fang-Qi
2016-01-01
The ground and first excited 0+ states of the {156-172}Er isotopes are analyzed in the framework of the generator coordinate method. The shape parameter beta is used to generate wave functions with different deformations which together with the two-quasiparticle states built on them provide a set of states. An angular momentum and particle number projection of the latter spawn the basis states of the generator coordinate method. With this ansatz and using the separable pairing plus quadrupole interaction we obtain a good agreement with the experimental spectra and E2 transition rates up to moderate spin values. The structure of the wave functions suggests that the first excited 0+ states in the soft Er isotopes are dominated by shape fluctuations, while in the well deformed Er isotopes the two-quasiparticle states are more relevant. In between both degrees of freedom are necessary .
Description of mixed symmetry states in 96Ru using IBM-2
Zhang, DaLi; Mu, ChengFu
2017-04-01
We have investigated the properties of low-lying states in 96Ru within the framework of the neutron-proton interacting boson model (IBM-2), with special attention paid to the characteristics of the mixed symmetry states. By considering the relative energy of d proton boson to be different from that of neutron boson, the level energies and M1, E2 transition strengths have been calculated. The IBM-2 calculation is consistent with the experimental data of 96Ru both quantitatively and qualitatively. Particularly, the strong M1 transition between the 42 + and 41 + states has been reproduced nicely. The calculated results show that the M1 transition strength of B( M1; 42 + → 41 +) in 96Ru can be described successfully by the IBM-2.
Analysis of the /sup 16/O( p,2p)/sup 15/N reaction at a proton energy 50 MeV
Energy Technology Data Exchange (ETDEWEB)
Boikova, N.F.; Vdovin, A.I.; Golikov, I.G.; Loshchakov, I.I.
1986-02-01
The /sup 16/O( p,2p)/sup 15/N reaction has been studied at a proton energy 50 MeV in the entire phase space, and in a symmetric coplanar geometry. Spectra differential in angle and energy have been obtained for the secondary protons and residual nuclei. The theoretical analysis of the data obtained has been carried out with inclusion of quasifree knockout and core polarization. In the quasifree approximation we have used the nonlocal realistic t matrix of free proton-proton scattering. The coupling constants which determine virtual excitations in the region of giant resonances of /sup 15/N for E1 and E2 transitions have been found. Agreement with experiment is obtained only under the condition of coherent summation of the amplitudes of the two processes considered.
Isomers and oblate collectivity at high spin in neutron-rich Pt isotopes
Directory of Open Access Journals (Sweden)
Tandel S.K.
2016-01-01
Full Text Available Isomers and high-spin structures with rotation-aligned oblate configurations have been studied in several Pt isotopes. The 12+ states in the even Pt isotopes from 192–198Pt are found to be metastable, and have (i13/22 neutron character. The progression of E2 transition probabilities from the 12+ to 10+ states across the Pt isotopic chain implies reduction in collectivity, followed by an abrupt decrease at N=120 (198Pt. This behavior is quite distinct from the gradual decrease of B(E2 values near the respective ground states. A large contribution from aligned angular momentum, to the rotational sequences built on the 12+ states, is visible. This is due to the relatively small crossing frequencies for nucleons in low-Ω orbitals at oblate deformation in comparison to higher values for prolate shapes. As a result, oblate rotation is found to be increasingly favored for higher neutron numbers.
The anomalous quadrupole collectivity in Te isotopes
Qi, Chong
2016-01-01
We present systematic calculations on the spectroscopy and transition properties of even-even Te isotopes by using the large-scale configuration interaction shell model approach with a realistic interaction. These nuclei are of particular interest since their yrast spectra show a vibrational-like equally-spaced pattern but the few known E2 transitions show anomalous rotational-like behavior, which cannot be reproduced by collective models. Our calculations reproduce well the equally-spaced spectra of those isotopes as well as the constant behavior of the $B(E2)$ values in $^{114}$Te. The calculated $B(E2)$ values for neutron-deficient and heavier Te isotopes show contrasting different behaviors along the yrast line. The $B(E2)$ of light isotopes can exhibit a nearly constant bevavior upto high spins. We show that this is related to the enhanced neutron-proton correlation when approaching $N=50$.
Shell-model configuration-interaction description of quadrupole collectivity in Te isotopes
Qi, Chong
2016-09-01
Systematic calculations on the spectroscopy and transition properties of even-even Te isotopes are carried out by using the large-scale shell-model configuration-interaction approach with a realistic interaction. These nuclei are of particular interest since their yrast spectra show a vibrational-like equally spaced pattern whereas the few known E 2 transitions show rotational-like behavior. This cannot be explained by available collective models. My calculations reproduce well the equally spaced spectra of those isotopes as well as the constant behavior for the B (E 2 ) values of 114Te. The calculated B (E 2 ) values of neutron-deficient and heavier Te isotopes show contrasting different behaviors along the yrast line. The B (E 2 ) of light isotopes can exhibit a nearly constant behavior up to high spins. It is shown that this is related to the enhanced neutron-proton correlation when approaching N =50 .
Absolute Transition Probabilities from the 453.1 keV Level in {sup 183}W
Energy Technology Data Exchange (ETDEWEB)
Malmskog, S.G.
1966-10-15
The half life of the 453.1 keV level in {sup 183}W has been measured by the delayed coincidence method to 18.4 {+-} 0.5 nsec. This determines twelve absolute M1 and E2 transition probabilities, out of which nine are K-forbidden. All transition probabilities are compared with the single particle estimate. The three K-allowed E2, {delta}K = 2 transition rates to the 1/2{sup -} (510) rotational band are furthermore compared with the Nilsson model. An attempt to give a quantitative explanation of the observed transition rates has been made by including the effects from admixtures into the single particle wave functions.
Conversion electron study of {sup 110}Cd: Evidence of new E0 branches
Energy Technology Data Exchange (ETDEWEB)
Jigmeddorj, B.; Garrett, P.E.; Diaz Varela, A.; Bangay, J.C.; Demand, G.A.; Green, K.L.; Rand, E.T.; Sumithrarachchi, C.; Svensson, C.E.; Wong, J. [University of Guelph, Department of Physics, Guelph, ON (Canada); Ball, G.C.; Garnsworthy, A.B.; Hackman, G. [TRIUMF, Vancouver, BC (Canada); Cross, D.S. [Simon Fraser University, Department of Chemistry, Burnaby, BC (Canada); Kulp, W.D.; Wood, J.L. [Georgia Institute of Technology, School of Physics, Atlanta, GA (United States); Leach, K.G. [University of Guelph, Department of Physics, Guelph, ON (Canada); TRIUMF, Vancouver, BC (Canada); Orce, J.N. [TRIUMF, Vancouver, BC (Canada); University of the Western Cape, Department of Physics, Bellville (South Africa); Triambak, S. [TRIUMF, Vancouver, BC (Canada); University of the Western Cape, Department of Physics, Bellville (South Africa); iThemba LABS, Somerset West (South Africa); Yates, S.W. [University of Kentucky, Departments of Chemistry and Physics and Astronomy, Lexington, KY (United States)
2016-02-15
Excited states of {sup 110}Cd were studied with conversion electron spectroscopy following the β{sup +}/EC decay of {sup 110}In. Internal conversion coefficients from K-shell electrons are extracted from γ - e{sup -} coincidences and compared with expected values for E1, M1, and E2 transitions, allowing the assignment of the transition multipolarities. The α{sub K} values for transitions connecting the 4{sup +} and 6{sup +} members of the deformed intruder band and the ground-state band show evidence for E0 components. The extracted ρ{sup 2}(E0).10{sup 3} value for the 4{sup +}{sub 3}→4{sup +}{sub 1} 708 keV transition is determined to be 106{sup +98}{sub -91}. (orig.)
Positive parity low spin states of odd-mass tellurium isotopes
Yazar, Harun Reşit
2006-11-01
In this work, we analyse the positive parity of states of odd-mass nucleus within the framework of interacting boson fermion model. The result of an IBFM-1 multilevel calculation with the lg 9/2, 2d 5/2, 2d 3/2, 3s 1/2 and one level, 1h 11/2 with negative parity, single particle orbits is reported for the positive parity states of the odd mass nucleus 123-125Te. Also, an IBM-1 calculation is presented for the low-lying states in the even-even 124-126Te core nucleus. The energy levels and B (E2) transition probabilities were calculated and compared with the experimental data. It was found that the calculated positive parity low spin state energy spectra of the odd-mass 123-125Te isotopes agree quite well with the experimental data.
X(3): an exactly separable {gamma}-rigid version of the X(5) critical point symmetry
Energy Technology Data Exchange (ETDEWEB)
Bonatsos, Dennis [Institute of Nuclear Physics, NCSR ' Demokritos' , GR-15310 Aghia Paraskevi, Attiki (Greece)]. E-mail: bonat@inp.demokritos.gr; Lenis, D. [Institute of Nuclear Physics, NCSR ' Demokritos' , GR-15310 Aghia Paraskevi, Attiki (Greece)]. E-mail: lenis@inp.demokritos.gr; Petrellis, D. [Institute of Nuclear Physics, NCSR ' Demokritos' , GR-15310 Aghia Paraskevi, Attiki (Greece)]. E-mail: petrellis@inp.demokritos.gr; Terziev, P.A. [Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72 Tzarigrad Road, BG-1784 Sofia (Bulgaria)]. E-mail: terziev@inrne.bas.bg; Yigitoglu, I. [Institute of Nuclear Physics, NCSR ' Demokritos' , GR-15310 Aghia Paraskevi, Attiki (Greece) and Hasan Ali Yucel Faculty of Education, Istanbul University, TR-34470 Beyazit, Istanbul (Turkey)]. E-mail: yigitoglu@istanbul.edu.tr
2006-01-12
A {gamma}-rigid version (with {gamma}=0) of the X(5) critical point symmetry is constructed. The model, to be called X(3) since it is proved to contain three degrees of freedom, utilizes an infinite well potential, is based on exact separation of variables, and leads to parameter free (up to overall scale factors) predictions for spectra and B(E2) transition rates, which are in good agreement with existing experimental data for {sup 172}Os and {sup 186}Pt. An unexpected similarity of the {beta}{sub 1}-bands of the X(5) nuclei {sup 150}Nd, {sup 152}Sm, {sup 154}Gd, and {sup 156}Dy to the X(3) predictions is observed.
Institute of Scientific and Technical Information of China (English)
Yao Jiang-Ming; Meng Jie; D. Pena Arteaga; P. Ring
2008-01-01
A full three-dimensional angular momentum projection on top of a triaxial relativistic mean-field calculation is implemented for the first time. The underlying Lagrangian is a point coupling model and pairing correlations are taken into account by a monopole force. This method is applied for the low-lying excited states in 24Mg. Good agreement with the experimental data is found for the ground state properties. A minimum in the potential energy surface for the 2+ state, with β≈ 0.55, γ≈ 10°, is used as the basis to investigate the rotational energyspectrum as well as the corresponding B(E2) transition probabilities as compared to the available data.
Yao, J M; Arteaga, D Pena; Ring, P; 10.1088/0256-307X/25/10/024
2008-01-01
A full three-dimensional angular momentum projection on top of a triaxial relativistic mean-Geld calculation is implemented for the first time. The underlying Lagrangian is a point coupling model and pairing correlations are taken into account by a monopole force. This method is applied for the low-lying excited states in 24Mg. Good agreement with the experimental data is found for the ground state properties. A minimum in the potential energy surface for the 2+ state, with beta = 0.55, gamma = 10 deg, is used as the basis to investigate the rotational energy spectrum as well as the corresponding B(E2) transition probabilities as compared to the available data.
Effects of proton angular momentum alignment on the two-shears-like mechanism in 101Pd
Zhang, Zhen-Hua
2016-09-01
The recently observed possible antimagnetic rotation band in 101Pd is investigated by the cranked shell model with pairing correlations treated by a particle-number-conserving method, in which the blocking effects are taken into account exactly. The experimental moments of inertia and reduced B (E 2 ) transition probabilities and their variations with the rotational frequency ω are well reproduced. By analyzing the ω dependence of the occupation probability of each cranked Nilsson orbital near the Fermi surface and the contributions of valence orbitals in each major shell to the total angular momentum alignment, the upbending mechanism of ν h11 /2 in 101Pd is understood clearly. The proton angular momentum alignment and its influence on the two-shears-like mechanism are also discussed.
Population of rotational bands in superheavy nuclei
Directory of Open Access Journals (Sweden)
Antonenko N.V.
2012-02-01
Full Text Available Using the statistical approach, we study the population of ground-state rotational bands of superheavy nuclei produced in the fusion-evaporation reactions 208Pb(48Ca, 2n254No, 206Pb(48Ca, 2n252No, and 204Hg(48Ca, 2n250Fm. We calculate relative intensities of E2-transitions between the rotational states and entry spin distributions of the residual nuclei, evaporation residue cross sections, and excitation functions for these reactions. Fermi-gas model is used for the calculation of level density, and damping of shell effects both with excitation energy and angular momentum is taking into account. The results are in a good agreement with the experiment data.
Smirnova, N A; Mizusaki, T; Van Isacker, P
2000-01-01
The interrelation between the octupole phonon and the low-lying proton-neutron mixed-symmetry quadrupole phonon in near-spherical nuclei is investigated. The one-phonon states decay by collective E3 and E2 transitions to the ground state and by relatively strong E1 and M1 transitions to the isoscalar 2 sup + sub 1 state. We apply the proton-neutron version of the interacting boson model including quadrupole and octupole bosons ( sdf -IBM-2). Two F -spin symmetric dynamical symmetry limits of the model, namely the vibrational and the gamma -unstable ones, are considered. We derive analytical formulae for excitation energies as well as B(E1) , B(M1) , B(E2) and B(E3) values for a number of transitions between low-lying states.
Partial dynamical symmetry in the symplectic shell model
Energy Technology Data Exchange (ETDEWEB)
Escher, J. [TRIUMF, Vancouver, British Columbia (Canada); Leviatan, A. [Hebrew Univ., Racah Inst. of Physics, Jerusalem (Israel)
2000-08-01
We present an example of a partial dynamical symmetry (PDS) in an interacting fermion system and demonstrate the close relationship of the associated Hamiltonians with a realistic quadrupole-quadrupole interaction, thus shedding light on this important interaction. Specifically, in the framework of the symplectic shell model of nuclei, we prove the existence of a family of fermionic Hamiltonians with partial SU(3) symmetry. We outline the construction process for the PDS eigenstates with good symmetry and give analytic expressions for the energies of these states and E2 transition strengths between them. Characteristics of both pure and mixed-symmetry PDS eigenstates are discussed and the resulting spectra and transition strengths are compared to those of real nuclei. The PDS concept is shown to be relevant to the description of prolate, oblate, as well as triaxially deformed nuclei. Similarities and differences between the fermion case and the previously established partial SU(3) symmetry in the interacting boson model are considered. (author)
Partial Dynamical Symmetry in the Symplectic Shell Model
Escher, J; Escher, Jutta; Leviatan, Amiram
2002-01-01
We present an example of a partial dynamical symmetry (PDS) in an interacting fermion system and demonstrate the close relationship of the associated Hamiltonians with a realistic quadrupole-quadrupole interaction, thus shedding new light on this important interaction. Specifically, in the framework of the symplectic shell model of nuclei, we prove the existence of a family of fermionic Hamiltonians with partial SU(3) symmetry. We outline the construction process for the PDS eigenstates with good symmetry and give analytic expressions for the energies of these states and E2 transition strengths between them. Characteristics of both pure and mixed-symmetry PDS eigenstates are discussed and the resulting spectra and transition strengths are compared to those of real nuclei. The PDS concept is shown to be relevant to the description of prolate, oblate, as well as triaxially deformed nuclei. Similarities and differences between the fermion case and the previously established partial SU(3) symmetry in the Interact...
Ayangeakaa, A D; Janssens, R V F; Carpenter, M P; Albers, M; Alcorta, M; Baugher, T; Bertone, P F; Chiara, C J; Chowdhury, P; David, H M; Deacon, A N; DiGiovine, B; Gade, A; Hoffman, C R; Kondev, F G; Lauritsen, T; Lister, C J; McCutchan, E A; Moerland, D S; Nair, C; Rogers, A M; Seweryniak, D
2015-01-01
An extensive study of the level structure of 61Co has been performed following the complex 26Mg(48Ca, 2a4npg)61Co reaction at beam energies of 275, 290 and 320 MeV using Gammasphere and the Fragment Mass Analyzer (FMA). The low-spin structure is discussed within the framework of shell-model calculations using the GXPF1A effective interaction. Two quasi-rotational bands consisting of stretched-E2 transitions have been established up to spins I = 41/2 and (43/2), and excitation energies of 17 and 20 MeV, respectively. These are interpreted as signature partners built on a neutron {\
Singh, P.; Kharb, S.; Singh, M.
2014-02-01
The effects of electric quadrupole ( E2) and dipole-quadrupole interference ( E1- E2) terms in the Coulomb breakup of 15C have been investigated within the framework of eikonal approximation. The sensitivity of Coulomb breakup cross section, differential in relative energy and Longitudinal Momentum Distribution (LMD) of core fragments, towards these terms have been examined. A very small (1% of E1) contribution of E2 transition has been predicted in integrated Coulomb breakup cross section. Further it is also found that the inclusion of E2 and E1- E2 terms introduces a small asymmetry in the peak of relative energy spectrum and also increases the peak height of the spectrum. The contribution of dipole-quadrupole interference terms is clearly shown in LMD, as it introduces an asymmetry in the shape of LMD and enhances the matching between the data and predictions.
Bisoi, Abhijit; Sarkar, M. Saha; Sarkar, S.; Ray, S.; Pramanik, D.; Kshetri, R.; Nag, Somnath; Selvakumar, K.; Singh, P.; Goswami, A.; Saha, S.; Sethi, J.; Trivedi, T.; Naidu, B. S.; Donthi, R.; Nanal, V.; Palit, R.
2014-08-01
High spin states of S33 populated through 27Al(12C,αpn)S33 reaction at E(C12)=40 MeV have been studied using the Indian National Gamma Array (INGA) facility. The level scheme was extended and modified utilizing data from the γ -γ coincidence, directional correlation, and linear polarization measurements. Three levels of the negative parity yrast sequence were found to be connected by strong E2 transitions. The lifetimes of these states determined by the Doppler shift attenuation method have been utilized to study the evolution of collectivity with spin. Large basis shell model calculations have been performed to understand the microscopic origin of these levels.
Three Magnetic Rotation Bands in 84^Rb
Shen, Shuifa; Han, Guangbing; Wen, Shuxian; Yan, Yupeng; Wu, Xiaoguang; Zhu, Lihua; He, Chuangye; Li, Guangsheng
2016-01-01
High-spin states in $^{84}$Rb are studied by using the $^{70}$Zn($^{18}$O, p3n)$^{84}$Rb reaction at beam energy of 75 MeV. Three high-lying negative-parity bands are established, whose level spacings are very regular, i.e., there don't exist signature splitting. The dipole character of the transitions of these three bands is assigned by the $\\gamma$-$\\gamma$ directional correlations of oriented states (DCO) intensity ratios and the multipolarity M1 is suggested by the analogy to multiparticle excitations in neighboring nuclei. The strong M1 and weak or no E2 transitions are observed. All these characteristic features show they are magnetic rotation bands.
Particle-number conserving analysis of the high-spin structure of $^{159}$Ho
Zhang, Zhen-Hua
2016-01-01
The high-spin rotational bands in odd-$Z$ nuclei $^{159}$Ho ($Z=67$) are investigated using the cranked shell model with the pairing correlations treated by a particle-number conserving method, in which the blocking effects are taken into account exactly. The experimental moments of inertia and alignments and their variations with the rotational frequency $\\hbar\\omega$ are reproduced very well by the calculations. The splitting between the signature partners of the yrast band $7/2^-[523]$ is discussed and the splitting of the excited band $7/2^+[404]$ above $\\hbar\\omega \\sim 0.30$~MeV is predicted due to the level crossing with $1/2^+[411]$. The calculated $B(E2)$ transition probabilities are also suggested for future experiments.
Energy spectra and quadrupole transition probabilities of 124-130Ba
Sabri, H
2016-01-01
In this paper, we have studied the energy spectra and B(E2) transition probabilities of 124-130Ba isotopes in the shape phase transition region between the spherical and gamma unstable deformed shapes. We have used a transitional Interacting Boson Model Hamiltonian which is based on affine SU(1,1) Lie Algebra in the both IBM-1 and 2 versions and also the Catastrophe theory in combination with a coherent state formalism to generate energy surfaces and determine the exact values of control parameters. Our results for control parameters suggest a combination of U(5) and SO(6) dynamical symmetries in this isotopic chain. Also, the theoretical predictions can be rather well reproduce the experimental counterparts when the control parameter is approached to the SO(6) limit.
Description of mixed symmetry states in 96Ru using IBM-2
Zhang, DaLi; Mu, ChengFu
2017-04-01
We have investigated the properties of low-lying states in 96Ru within the framework of the neutron-proton interacting boson model (IBM-2), with special attention paid to the characteristics of the mixed symmetry states. By considering the relative energy of d proton boson to be different from that of neutron boson, the level energies and M1, E2 transition strengths have been calculated. The IBM-2 calculation is consistent with the experimental data of 96Ru both quantitatively and qualitatively. Particularly, the strong M1 transition between the 42 + and 41 + states has been reproduced nicely. The calculated results show that the M1 transition strength of B( M1; 42 + → 41 +) in 96Ru can be described successfully by the IBM-2.
Bose–Fermi symmetry in the odd–even gold isotopes
Energy Technology Data Exchange (ETDEWEB)
Thomas, T.; Régis, J.-M.; Jolie, J.; Heinze, S. [Institute for Nuclear Physics, University of Cologne, Zülpicher Straße 77, D-50937 Köln (Germany); Albers, M. [Institute for Nuclear Physics, University of Cologne, Zülpicher Straße 77, D-50937 Köln (Germany); Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Bernards, C. [Institute for Nuclear Physics, University of Cologne, Zülpicher Straße 77, D-50937 Köln (Germany); WNSL, Yale University, P.O. Box 208120, New Haven, CT 06520-8120 (United States); Fransen, C.; Radeck, D. [Institute for Nuclear Physics, University of Cologne, Zülpicher Straße 77, D-50937 Köln (Germany)
2014-05-15
In this work the results of an in-beam experiment on {sup 195}Au are presented, yielding new spins, multipole mixing ratios, and new low-lying states essential for the understanding of this nucleus. The positive-parity states from this work together with compiled data from the available literature for {sup 185–199}Au are compared to Interacting Boson Fermion Model calculations employing the Spin(6) Bose–Fermi symmetry. The evolution of the parameters for the τ splitting and the J splitting reveals a smooth behavior. Thereby, a common description based on the Bose–Fermi symmetry is found for {sup 189–199}Au. Furthermore, the calculated E2 transition strengths are compared to experimental values with fixed effective boson and fermion charges for all odd–even gold isotopes, emphasizing that the Spin(6) Bose–Fermi symmetry is valid for the gold isotopes.
Kaneko, K; Sun, Y; Tazaki, S
2015-01-01
The recently-proposed effective shell-model interaction, the pairing-plus-multipole Hamiltonian with the monopole interaction obtained by empirical fits starting from the monopole-based universal force (PMMU), is systematically applied to nuclei of the pf5/2g9/2 shell region. It is demonstrated that the calculation describes reasonably well a wide range of experimental data, including not only the low-lying and high-excitation spectra, E2 transitions, quadrupole moments, and magnetic moments, but also the binding energies, for Ni, Cu, Zn, Ga, Ge, As, and Se isotopes with A=64-80. In particular, a structure of the neutron-rich Ge and Se isotopes is discussed in detail.
De Witte, H; Borzov, I N; Caurier, E; Cederkäll, J; De Smet, A; Eckhaudt, S; Fedorov, D V; Fedosseev, V; Franchoo, S; Górska, M; Grawe, H; Huber, G; Huyse, M; Janas, Z; Köster, U; Kurcewicz, W; Kurpeta, J; Plochocki, A; Van Duppen, P; Van de Vel, K; Weissman, L
2004-01-01
The neutron-rich isotope /sup 218/Bi has been produced in proton- induced spallation of a uranium carbide target at the ISOLDE facility at CERN, extracted from the ion source by the pulsed-release technique and resonant laser ionization, and its beta decay is studied for the first time. A half-life of 33(1)s was measured and is discussed in the self-consistent continuum-quasi particle-random- phase approximation framework that includes Gamow-Teller and first- forbidden transitions. A level scheme was constructed for /sup 218 /Po, and a deexcitation pattern of stretched E2 transitions 8/sup +/ to 6/sup +/ to 4/sup +/ to 2/sup +/ to 0/sup +/ to the ground state is suggested. Shell-model calculations based on the Kuo-Herling interaction reproduce the experimental results satisfactorily. (28 refs).
Phase transition studies of the odd-mass 123-135Xe isotopes based on SU(1,1) algebra in IBFM
Jafarizadeh, M. A.; Fouladi, N.; Ghapanvari, M.; Fathi, H.
2016-07-01
In this paper, we have investigated the positive-parity states in the odd-mass transitional 123-135Xe isotopes within the framework of the interacting boson-fermion model. Two solvable extended transitional Hamiltonians which are based on SU(1,1) algebra are employed to provide an investigation of quantum phase transition (QPT) between the spherical and deformed gamma — unstable shapes along the chain of Xe isotopes. The low-states energy spectra and B(E2) values for these nuclei have been calculated and compared with the experimental data. The predicted excitation energies and B(E2) transition rates of the odd isotopes are found to agree well with the experimental data. We have also analyzed the critical behavior of even-odd Xe isotopes via Catastrophe Theory in combination with a coherent state formalism to generate energy surfaces and special isotopes which are the best candidates for the critical point are identified.
Astrophysical S-factor for $^6$Li$(p,\\gamma)$$^7$Be in the coupled-channel Gamow shell model
Dong, G X; Michel, N; Płoszajczak, M
2015-01-01
We have applied the Gamow shell model (GSM) in the coupled-channel representation to study the astrophysical $S$-factor for the proton radiative capture reaction of $^6$Li. Reaction channels are built by coupling the proton wave function expanded in different partial waves with the GSM wave functions of the ground state ($1^+$) and the excited states ($3^+_1$, $0^+_1$ and $2^+_1$) of $^6$Li. All relevant $E1$, $M1$, and $E2$ transitions from the initial continuum states in $^7$Be to the final bound states (${3/2}^-_1$ and ${1/2}^-_1$) states are included. It is found that the calculated total astrophysical $S$ factor for this reaction agrees well with the experimental data.
Longitudinal Wobbling in $^{133}$La
Biswas, S; Garg, U; Bhat, G H; Frauendorf, S; Li, W; Sheikh, J A; Sethi, J; Saha, S; Singh, Purnima; Choudhury, D; Matta, J T; Ayangeakaa, A D; Dar, W >; Singh, V; Sihotra, S
2016-01-01
Excited states of $^{133}$La have been investigated to search for the wobbling excitation mode in the low-spin regime. Wobbling bands with $n_\\omega$ = 0 and 1 are identified along with the interconnecting $\\Delta I$ = 1, $E2$ transitions, which are regarded as fingerprints of the wobbling motion. An increase in wobbling frequency %of the $n_\\omega$ = 1 band with spin implies longitudinal wobbling for $^{133}$La, in contrast with the case of transverse wobbling observed in $^{135}$Pr. This is the first observation of a longitudinal wobbling band in nuclei. The experimental observations are accounted for by calculations using the quasiparticle triaxial rotor with harmonic frozen approximation and the triaxial projected shell model approaches, which attribute the appearance of longitudinal wobbling to the early alignment of an h$_{11/2}$ neutron pair.
Improved Value for the Energy Splitting of the Ground-State Doublet in the Nucleus 229Th
Beck, B R; Beiersdorfer,1 P; Brown, G V; Moody, J K; Wu, C Y; Wilhelmy, J B; Porter, F S; Kilbourne, C A; Kelley, R L
2010-01-01
We have made an improved estimate of the 229mTh isomer energy. The new value 7.8(5) eV includes an estimate of spectral contamination due to the out-of-band E2 transition from the 42.43-keV 7/2+ member of the [633] ground state band to the 3/2+ [631] 229mTh bandhead. We estimate a 2% branching ratio for this unobserved transition in the 42.43-keV 7/2+ [633] deexcitation. The excitation of the 229mTh level is increased from the previously reported value of 7.6(5) eV to the new value of 7.8(5) eV when this branch is included in the analysis.
Improved Value for the Energy Splitting of the Ground-State Doublet in the Nucleus 229mTh
Energy Technology Data Exchange (ETDEWEB)
Beck, B R; Wu, C; Beiersdorfer, P; Brown, G V; Becker, J A; Moody, K J; Wilhelmy, J B; Porter, F S; Kilbourne, C A; Kelley, R L
2009-07-16
We have made an improved estimate of the {sup 229m}Th isomer energy. The new value, 7.8(5) eV, includes an estimate of possible spectral contamination effects due to the out-of-band E2 transition from the 42.43-keV 7/2+ member of the [633] ground state band to the 3/2+ [631] {sup 229m}Th bandhead and so a weak and unresolved transition a few eV different in energy. We estimate a 2% branching ratio for this unobserved transition in the 42.43-keV 7/2+ [633] deexcitation. The excitation of the {sup 229m}Th level is increased from the previously reported value of 7.6(5) eV to the new best value of 7.8(5) eV when this branch is included in the analysis.
Coexisting shape- and high-K isomers in the shape transitional nucleus {sup 188}Pt
Energy Technology Data Exchange (ETDEWEB)
Mukhopadhyay, S., E-mail: somm@barc.gov.in [Nuclear Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Biswas, D.C. [Nuclear Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Tandel, S.K. [UM-DAE Centre for Excellence in Basic Sciences, Mumbai 400098 (India); Danu, L.S.; Joshi, B.N.; Prajapati, G.K. [Nuclear Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Nag, Somnath [Dept. of Physics, IIT Kharagpur, Kharagpur 721302 (India); Trivedi, T.; Saha, S.; Sethi, J.; Palit, R. [Dept. of Nuclear and Atomic Physics, TIFR, Mumbai 400005 (India); Joshi, P.K. [Homi Bhabha Centre for Science Education, TIFR, Mumbai 400088 (India)
2014-12-12
A high-spin study of the shape transitional nucleus {sup 188}Pt reveals the unusual coexistence of both shape- and K-isomeric states. Reduced B(E2) transition probabilities for decays from these states inferred from the data clearly establish their hindered character. In addition to other excited structures, a rotational band built upon the K isomer is identified, and its configuration has been assigned through an analysis of alignments and branching ratios. The shape evolution with spin in this nucleus has been inferred from both experimental observables and cranking calculations. The yrast positive parity structure appears to evolve from a near-prolate deformed shape through triaxial at intermediate excitation, and eventually to oblate at the highest spins.
Hartman, H; Lundin, P; Schef, P; Hibbert, A; Lundberg, H; Mannervik, S; Norlin, L -O; Royen, P
2008-01-01
Context. In many plasmas, long-lived metastable atomic levels are depopulated by collisions (quenched) before they decay radiatively. In low-density regions, however, the low collision rate may allow depopulation by electric dipole (E1) forbidden radiative transitions, so-called forbidden lines (mainly M1 and E2 transitions). If the atomic transition data are known, these lines are indicators of physical plasma conditions and used for abundance determination. Aims. Transition rates can be derived by combining relative intensities between the decay channels, so-called branching fractions (BFs), and the radiative lifetime of the common upper level. We use this approach for forbidden [Sc ii] lines, along with new calculations. Methods. Neither BFs for forbidden lines, nor lifetimes of metastable levels, are easily measured in a laboratory. Therefore, astrophysical BFs measured in Space Telescope Imaging Spectrograph (STIS) spectra of the strontium filament of Eta Carinae are combined with lifetime measurements u...
Katsuma, M
2015-01-01
The radiative capture cross sections of $^{12}$C($\\alpha$,$\\gamma$)$^{16}$O and derived reaction rates are calculated from the direct capture potential model. The resulting $S$-factor at low energies is found to be dominated by $E$2 transition to the $^{16}$O ground state. The $E$1 and $E$2 $S$-factors at $E_{c.m.}=0.3$ MeV are $S_{E1}\\approx3$ keV~b and $S_{E2}=150^{+41}_{-17}$ keV~b, respectively. The sum of the cascade transition through the excited state of $^{16}$O is $S_{\\rm casc}= 18\\pm4.5$ keV~b. The derived reaction rates at low temperatures seem to be concordant with those from the previous evaluation. For astrophysical applications, our reaction rates below $T_9=3$ are provided in an analytic expression.
Evidence for a smooth onset of deformation in the neutron-rich Kr isotopes
Albers, M; Nomura, K; Blazhev, A; Jolie, J; Mucher, D; Bastin, B; Bauer, C; Bernards, C; Bettermann, L; Bildstein, V; Butterworth, J; Cappellazzo, M; Cederkall, J; Cline, D; Darby, I; Das Gupta, S; Daugas, J M; Davinson, T; De Witte, H; Diriken, J; Filipescu, D; Fiori, E; Fransen, C; Gaffney, L P; Georgiev, G; Gernhauser, R; Hackstein, M; Heinze, S; Hess, H; Huyse, M; Jenkins, D; Konki, J; Kowalczyk, M; Kroll, T; Krucken, R; Litzinger, J; Lutter, R; Marginean, N; Mihai, C; Moschner, K; Napiorkowski, P; Nara Singh, B S; Nowak, K; Otsuka, T; Pakarinen, J; Pfeiffer, M; Radeck, D; Reiter, P; Rigby, S; Robledo, L M; Rodriguez-Guzman, R; Rudigier, M; Sarriguren, P; Scheck, M; Seidlitz, M; Siebeck, B; Simpson, G; Thole, P; Thomas, T; Van de Walle, J; Van Duppen, P; Vermeulen, M; Voulot, D; Wadsworth, R; Wenander, F; Wimmer, K; Zell, K O; Zielinska, M
2012-01-01
The neutron-rich nuclei $^{94,96}$Kr were studied via projectile Coulomb excitation at the REX-ISOLDE facility at CERN. Level energies of the first excited 2$^{+}$ states and their absolute $E2$ transition strengths to the ground state are determined and discussed in the context of the $E(2^{+}_{1})$ and $B(E2;2^{+}_{1} \\rightarrow 0^{+}_{1})$ systematics of the krypton chain. Contrary to previously published results no sudden onset of deformation is observed. This experimental result is supported by a new proton-neutron interacting boson model calculation based on the constrained Hartree-Fock-Bogoliubov approach using the microscopic Gogny-D1M energy density functional.
Kanada-Enyo, Y
2004-01-01
Systematic analysis of the deformations of proton and neutron densities in even-even C isotopes was done based on the method of antisymmetrized molecular dynamics. The $E2$ transition strength was discussed in relation to the deformation. We analyze the $B(E2;2^+_1\\to 0^+_1)$ in $^{16}$C, which has been recently measured to be abnormally small. The results suggest the difference of the deformations between proton and neutron densities in the neutron-rich C isotopes. It was found that stable proton structure in C isotopes plays an important role in the enhancement the neutron skin structure as well as in the systematics of $B(E2)$ in the neutron-rich C.
Energy Technology Data Exchange (ETDEWEB)
Smirnova, N.A.; Van Isacker, P. [Grand Accelerateur National d' Ions Lourds (GANIL), 14 - Caen (France); Smirnova, N.A [Paris-11 Univ., 91 - Orsay (France). Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse]|[Institute for Nuclear Physics, Moscow State University (Russian Federation); Pietralla, N. [Institut fur Kernphysik, Universitat zu Koln (Germany)]|[Yale Univ., New Haven, CT (United States). Wright Nuclear Structure Lab; Mizusaki, T. [Tokyo Univ. (Japan). Dept. of Physics
2000-07-01
The interrelation between the octupole phonon and the low-lying proton-neutron mixed-symmetry quadrupole in near-spherical nuclei is investigated. The one-phonon states decay by collective E3 and E2 transitions to the ground state and by relatively strong E1 and M1 transitions to the isoscalar 2{sup +}{sub 1} state. We apply the proton-neutron version of the Interacting Boson Model including quadrupole and octupole bosons (sdf-IBM-2). Two F-spin symmetric dynamical symmetry limits of the model, namely the vibrational and the {gamma}-unstable ones, are considered. We derived analytical formulae for excitation energies as well as B(E1), B(M1), B(E2), and B(E3) values for a number of transitions between low-lying states. The model well reproduces many known transition strengths in the near spherical nuclei {sup 142}Ce and {sup 94}Mo. (authors)
Electromagnetic transitions in multiple chiral doublet bands
Jia, Hui; Wang, Shou-Yu; Wang, Shuo; Liu, Chen
2016-01-01
Multiple chiral doublet bands (M$\\chi$D) in the $80$, 130 and $190$ mass regions are studied by the model of $\\gamma$=90$^{\\circ}$ triaxial rotor coupled with identical symmetric proton-neutron configurations. By selecting the suitable basis, the calculated wave functions are explicitly exhibited to be symmetric under the operator $\\hat{A}$, which is defined as rotation by $90^{\\circ}$ about 3-axis with the exchange of valance proton and neutron. We found that both $M1$ and $E2$ transitions are allowed between the levels with different values of $A$, while are forbidden between the levels with same values of $A$. Such a selection rule holds true for M$\\chi$D in different mass regions.
Institute of Scientific and Technical Information of China (English)
LI XIANG-DONG; TAN MING-LIANG; YI YOU-GEN; ZHANG ZHI-HONG; ZHU ZHENG-HE; ZHANG ZHI-HONG
2000-01-01
We provide systematic calculations about the energy levels, Einstein coefficients and oscillator strengths for electricquadrupole (E2) and magnetic quadrupole (M2) transitions between n=3 and n=2 of Ne-like systems by using the fullyrelativistic multi-configuration Dirac-Fock method. The oscillator strengths of the E2 transitions under Coulomb andBabshkin gauges are compared with each other and show the differences from 1.2 to 12 percent. We also found that theM2 line (0.37429 nm) with the biggest oscillator strengths in Ne-like Ag37+ mixes with the line (2p5 3/23s1/23d5/2)3/2 →gs(0.37427 nm) emitted by the Na-like Ag36+.
Singh, Gajendra; Puri, Nitin K.
2016-10-01
We have applied systematically enlarged multiconfiguration Dirac–Fock wavefunctions using Grasp2K to calculate the transition energies, oscillator strengths and transition probabilities for fine structure M1 and E2 transitions between the low-lying levels of the 3s23p5, 3s23p4, 3s23p3 and 3s23p2 configurations of highly charged tungsten ions from {{{W}}}57+ to {{{W}}}60+. Large wavefunction expansions are applied to calculate the transition probabilities, which are indispensable for calculating various plasma parameters accurately. In the present calculations, our theoretical data agrees well with that obtained in precise electron beam ion trap measurements, and is therefore important for the identification of weak forbidden lines for plasma diagnostic applications.
Determination of absolute internal conversion coefficients using the SAGE spectrometer
Sorri, J.; Greenlees, P. T.; Papadakis, P.; Konki, J.; Cox, D. M.; Auranen, K.; Partanen, J.; Sandzelius, M.; Pakarinen, J.; Rahkila, P.; Uusitalo, J.; Herzberg, R.-D.; Smallcombe, J.; Davies, P. J.; Barton, C. J.; Jenkins, D. G.
2016-03-01
A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for ground-state band E2 transitions show that the absolute internal conversion coefficients can be extracted using the methods described with a reasonable accuracy. In some cases of less intense transitions only an upper limit for the internal conversion coefficient could be given.
Microscopic cluster study of the sup 3 sup 1 Ne and sup 3 sup 2 Ne nuclei
Descouvemont, P
1999-01-01
We investigate the sup 3 sup 1 Ne and sup 3 sup 2 Ne neutron-rich nuclei by using the Generator Coordinate Method. The wave functions are defined by a sup 3 sup 0 Ne + n and sup 3 sup 0 Ne + n + n cluster structure, respectively. The binding energies of both systems are studied with different parameters of the nucleon-nucleon interaction, and are shown to be similar. Assuming the particle stability of sup 3 sup 2 Ne, the sup 3 sup 1 Ne nucleus is therefore predicted to be stable with respect to neutron decay. Spectroscopic properties (r.m.s. radii and E2 transition probabilities) are presented for both nuclei.
Determination of absolute internal conversion coefficients using the SAGE spectrometer
Energy Technology Data Exchange (ETDEWEB)
Sorri, J., E-mail: juha.m.t.sorri@jyu.fi [University of Jyvaskyla, Department of Physics, P.O. Box 35, FI-40014 University of Jyvaskyla (Finland); Greenlees, P.T.; Papadakis, P.; Konki, J. [University of Jyvaskyla, Department of Physics, P.O. Box 35, FI-40014 University of Jyvaskyla (Finland); Cox, D.M. [University of Jyvaskyla, Department of Physics, P.O. Box 35, FI-40014 University of Jyvaskyla (Finland); Department of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE (United Kingdom); Auranen, K.; Partanen, J.; Sandzelius, M.; Pakarinen, J.; Rahkila, P.; Uusitalo, J. [University of Jyvaskyla, Department of Physics, P.O. Box 35, FI-40014 University of Jyvaskyla (Finland); Herzberg, R.-D. [Department of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE (United Kingdom); Smallcombe, J.; Davies, P.J.; Barton, C.J.; Jenkins, D.G. [Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom)
2016-03-11
A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of {sup 154}Sm, {sup 152}Sm and {sup 166}Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for ground-state band E2 transitions show that the absolute internal conversion coefficients can be extracted using the methods described with a reasonable accuracy. In some cases of less intense transitions only an upper limit for the internal conversion coefficient could be given.
Towards the pair spectroscopy of the Hoyle state in 12C
Directory of Open Access Journals (Sweden)
Robertson K.A.
2012-10-01
Full Text Available The triple–alpha process leading to the formation of stable carbon in the Universe is one of the most important nuclear astrophysical processes. The radiative width of the so–called Hoyle state, involving the 7.654 MeV E0 and the 3.2148 MeV E2 transitions, is known with 10–12% accuracy. A novel, more direct approach to determining the width is proposed here, based on the measurement of the E0 and the E2 internal pair conversion intensities. We report on the development of a new magnetic pair spectrometer with high sensitivity for electron–positron pairs and with excellent energy resolution.
Institute of Scientific and Technical Information of China (English)
戴连荣; 张丹; 刘入菱; 张亚楠; 于欢; 刘琦
2015-01-01
The structure and property of 182 W nucleus will be investigated in the Interacting Boson Model with a new scheme of O(6) higher‐order term .The energy levels and B(E2) transition values are calculated with two different schemes of SU (3) quadrupole‐quadrupole interaction and O(6) cubic interaction for describing the rotational 182 W nucleus ,also compared with the experimental data .The results show that the new scheme can also describe the experimental low‐lying spectrum reasonably , especially the higher levels of ground band and βband .The results also show that both schemes can describe the experimental intraband B(E2) transitions .However ,for interband transitions ,the re‐sults from O (6) cubic interaction are better than those from SU (3) quadrupole‐quadrupole interac‐tion w hich is fully forbidden .%在相互作用玻色子模型中引入了一种新方案即 O （6）高阶项来系统研究转动核182 W的能级和电四极跃迁性质，并和传统方案及实验结果进行了对比分析，结果表明新方案也可以描述转动核182 W的结构和性质。研究发现，新方案不但对基带的高激发能级和β带的描述比传统方案更为合理，也可以更合理地描述电四极带间跃迁过程，而传统方案下带间跃迁是禁戒的。
Energy Technology Data Exchange (ETDEWEB)
Stanoiu, M.A
2003-01-01
This thesis deals with studies of nuclei far from the valley of stability produced at GANIL by projectile fragmentation at intermediate energies. It consists of two parts. The first one is dedicated to the study of very light exotic nuclei around N=14. This is the first time that online {gamma}-ray spectroscopy combined with the projectile fragmentation was used with radioactive incident beams at GANIL. The advantages and the limitations of this method were established. 40 different nuclei have been produced and studied at the same time. A strong dependence of the population of excited states on the type of projectile was observed. New information was obtained on the structure of the isotopes B{sup 14,15}, C{sup 17,18,19,20}, N{sup 18,19,20,21,22}, O{sup 22,23,24}, F{sup 24,25,26} and Ne{sup 29}. The level schemes obtained from this study have been compared with shell-model predictions. In particular, the energy of 1588(20) keV found for the first 2{sup +} excited state in C{sup 20}, as well as the non-existence of a bound state in O{sup 24}, show that the proton-neutron interaction plays an important role in the structure of these nuclei. In the second part, an experiment is presented concerning the neutron-rich isomer nuclei around Ni{sup 68} produced by the LISE spectrometer. The fast-timing method was applied for the first time for the study of nuclei produced by projectile fragmentation. Subnanosecond half-lives of several levels in Ni{sup 67,69,90} and Cu{sup 71,72} were measured simultaneously and with high precision. These results have allowed us to test the shell model predictions for several E2 transitions and their associated B(E2) transition probabilities. (author)
Near Threshold Coincident Electrofission of Uranium -238.
Dowell, David Harry
Using the 100% duty cycle electron beam from the University of Illinois MUSL-2 accelerator, inelastic electron scattering form factors have been measured in coincidence with the fission decay of ('238)U. Data was taken at effective elastic momentum transfers of .36, .41 .45 and .59 fm(' -1) and electron-fission fragment angular correlations were measured perpendicular to and along the momentum transfer axis. The beam energies used were 67.11, 56.91 and 46.49 MeV, with the outgoing electron detected at 60(DEGREES) and 80(DEGREES), relative to the beam direction. The electron energy resolution was .1% and the form factors were measured for excitation energies from 2 to 12 MeV. Thin films of scintillator plastic (.5 mg/cm('2)) were used to detect the fission fragments from a 1 mg/cm('2) UF(,4) target evaporated onto a .240 mg/cm('2) aluminum backing. A prominent, anisotropic threshold peak is seen in the coincident form factors. An analysis of the q-dependence of the data and of the angular correlation indicates the observed strength is E2. Fission threshold for this E2 strength is about 5.7 MeV as compared with 6 MeV for E1 decays. The peak itself is due to the onset of neutron competition at 6.15 MeV. The threshold region, when analyzed using a Gaussian K-distribution to describe the statistical density of K -states near the fission barrier, exhibits a step-like change in the value of K(,0)('2) at .7 MeV above threshold. This indicates a possible energy gap in the E2 transition states. The decay is isotropic above 7.5 MeV excitation energy. From 7 to 11.7 MeV, the distribution of E2/EO strength is relatively flat with the total strength in this region exhausting approximately 10% of an energy weighted sum rule. A comparison with hadron scattering experiments suggests that some of the strength near 11.5 MeV is due to the fission decay of the giant monopole resonance with a fission probability similar to that of E2 transitions.
Spectroscopy and lifetime measurements of states in $^{76}$Kr populated in $^{76}$Rb decay
Giannatiempo, A; Perego, A; Sona, P; Mach, H; Fogelberg, B; García-Borge, M J; Tengblad, O; Fraile-Prieto, L M; Aas, A J; Gulda, K; CERN. Geneva
2005-01-01
The properties of the excited states of $^{76}$Kr, populated in the decay of $^{76}$Rb produced at ISOLDE isotopic separator, have been investigated by using K-conversion electron, $\\gamma$-ray, and $\\gamma\\gamma$ coincidence measurements. The lifetimes of several levels have been measured by means of the Advanced Time-Delayed $\\beta\\gamma\\gamma (t)$ method. The identification of 19 new levels and 55 transitions and the information deduced on spin and/or parity of the observed states from K-conversion coefficients, log ft values and decay properties have led to an improved knowledge of the level scheme. In particular, six 1$^-$ states have been definitely identified and $J^{\\pi} =2^{-}$ has been assigned to the 2227 keV level, on which a band proposed to have negative-parity and even-spin had been previously observed. The strengths of the $E$0 and $E$2 transitions de-exciting the 0$^{+}_{2}$ and 0$^{+}_{3}$ states (the latter is here identified with the state at 1598 keV) have been measured. The experimental ...
Study on {sup 222-226}Th isotopes in the cranking framework
Energy Technology Data Exchange (ETDEWEB)
Ram, Daya; Devi, Rani; Khosa, S.K., E-mail: rani_rakwal@yahoo.co.in [Department of Physics and Electronics, University of Jammu, Jammu and Kashmir (India)
2013-08-15
The yrast spectra, quadrupole moments, quadrupole deformation parameters (β{sub 2}), non-axiality parameters (γ), root mean-square radii for protons and neutrons, occupation probabilities, moment of inertia (I), and B(E2) transition probabilities are calculated for {sup 222{sup -226}}Th in the cranked Hartree-Bogoliubov framework. The calculations employ a quadrupole-quadrupole plus pairing model of residual interaction operating in a reasonably large valence space outside the {sup 164}Pb core. Our calculations reproduce qualitatively the observed yrast spectra in {sup 222-226}Th up to spin 20{sup +}. The calculated results indicate that the non-axiality parameter decreases as one moves along the yrast states. The observed increase in deformation from {sup 222}Th to {sup 226}Th is due to the increase in the occupation of low-κ components of (2g{sub 9/2}){sub π} and (1{sub j15/2}){sub ν} orbits. The model parameters reproduce not only the moment of inertia, deformation, and transition probabilities but also the proton and neutron pairing gaps and are the most appropriate for cranking studies in this region. (author)
Negative parity low-spin states of even–odd {sup 187–197}Pt isotopes
Energy Technology Data Exchange (ETDEWEB)
Kassim, Huda H.; Sharrad, Fadhil I., E-mail: fadhil.altaie@gmail.com
2015-01-15
In this paper, the negative parity low-spin states of even–odd {sup 187–197}Pt isotopes have been studied within the framework of the Interacting Boson–Fermion Model (IBFM-1). The single fermion is assumed to be in one of the 2f5/2, 3p3/2 and 3p1/2 single-particle orbits. The calculated negative parity low-states energy spectra agree quite well with the experimental data. The B(E2) values have been also calculated and compared with the experimental data. The calculated energy levels and B(E2) are in good agreement with experimental data than that in the previous study for {sup 195}Pt isotope. Furthermore, the energy levels, electric quadrupole transition probabilities and the potential energy surface for even–even platinum isotopes (as core for even–odd nuclei) have been calculated within framework of the Interacting Boson Model (IBM-1). The predicted energy levels and B(E2) transition probabilities results are reasonably consistent with the experimental data. The contour plot of the potential energy surfaces shows all interesting nuclei are deformed and have γ-unstable-like characters.
Nucleon-pair states of even-even Sn isotopes based on realistic effective interactions
Cheng, Y. Y.; Qi, C.; Zhao, Y. M.; Arima, A.
2016-08-01
In this paper we study yrast states of 128,126,124Sn and 104,106,108Sn by using the monopole-optimized realistic interactions in terms of both the shell model (SM) and the nucleon-pair approximation (NPA). For yrast states of 128,126Sn and 104,106Sn, we calculate the overlaps between the wave functions obtained in the full SM space and those obtained in the truncated NPA space, and find that most of these overlaps are very close to 1. Very interestingly, for most of these states with positive parity and even spin or with negative parity and odd spin, the SM wave function is found to be well represented by one nucleon-pair basis state, viz., a simple picture of "nucleon-pair states" (nucleon-pair configuration without mixings) emerges. In 128,126Sn, the positive-parity (or negative-parity) yrast states with spin J >10 (or J >7 ) are found to be well described by breaking one or two S pairs in the 101+ (or 71-) state, i.e., the yrast state of seniority-two, spin-maximum, and positive-parity (or negative-parity), into non-S pair(s). Similar regularity is also pointed out for 104,106Sn. The evolution of E 2 transition rates between low-lying states in 128,126,124Sn is discussed in terms of the seniority scheme.
Xue, W X; Hagino, K; Li, Z P; Mei, H; Tanimura, Y
2014-01-01
The impurity effect of hyperon on atomic nuclei has received a renewed interest in nuclear physics since the first experimental observation of appreciable reduction of $E2$ transition strength in low-lying states of hypernucleus $^{7}_\\Lambda$Li. Many more data on low-lying states of $\\Lambda$ hypernuclei will be measured soon for $sd$-shell nuclei, providing good opportunities to study the $\\Lambda$ impurity effect on nuclear low-energy excitations. We carry out a quantitative analysis of $\\Lambda$ hyperon impurity effect on the low-lying states of $sd$-shell nuclei at the beyond-mean-field level based on a relativistic point-coupling energy density functional (EDF), considering that the $\\Lambda$ hyperon is injected into the lowest positive-parity ($\\Lambda_s$) and negative-parity ($\\Lambda_p$) states. We adopt a triaxially deformed relativistic mean-field (RMF) approach for hypernuclei and calculate the $\\Lambda$ binding energies of hypernuclei as well as the potential energy surfaces (PESs) in $(\\beta, \\g...
Nuclear Structure of the Closed Subshell Nucleus 90Zr Studied with the (n,n'(gamma)) Reaction
Energy Technology Data Exchange (ETDEWEB)
Garrett, P E; Younes, Y; Becker, J A; Bernstein, L A; Baum, E M; DiPrete, D P; Gatenby, R A; Johnson, E L; McGrath, C A; Yates, S W; Devlin, M; Fotiades, N; Nelson, R O; Brown, B A
2003-06-12
States in {sup 90}Zr have been observed with the (n,n{prime}{gamma}) reaction using both spallation and monoenergetic accelerator-produced neutrons. A scheme comprised of 81 levels and 157 transitions was constructed concentrating on levels below 5.6 MeV in excitation energy. Spins have been determined by considering data from all experimental studies performed for {sup 90}Zr. Lifetimes have been deduced using the Doppler-shift attenuation method for many of the states and transition rates have been obtained. A spherical shell-model interpretation in terms of particle-hole excitations assuming a {sup 88}Sr closed core is given. In some cases, enhancements in B(M1) and B(E2) values are observed that cannot be explained by assuming simple particle-hole excitations. Shell-model calculations using an extended f pg-shell model space reproduce the spectrum of excited states very well, and the gross features of the B(M1) and B(E2) transition rates. Transition rates for individual levels show discrepancies between calculations and experimental values.
No-Core MCSM calculation for $^{10}$Be and $^{12}$Be low-lying spectra
Liu, Lang; Shimizu, Noritaka; Utsuno, Yutaka; Roth, Robert
2011-01-01
The low-lying excited states of $^{10}$Be and $^{12}$Be are investigated within a no-core Monte Carlo Shell Model (MCSM) framework employing a realistic potential obtained via the Unitary Correlation Operator Method. The excitation energies of the 2$^+_1$ and 2$^+_2$ states and the B(E2; 2$^+_{1}\\rightarrow$ 0$^+_{g.s.}$) for $^{10}$Be in the MCSM with a treatment of spurious center-of-mass motion show good agreement with experimental data. The deformation properties of the 2$^+_1$, 2$^+_2$ states for $^{10}$Be and of the 2$^+_1$ state for $^{12}$Be are studied in terms of quadrupole moments, E2 transitions and the single-particle occupations. The triaxial deformation of $^{10}$Be is tested by the B(E2; 2$^+_{2}\\rightarrow$ 2$^+_{1}$) value. The removal of the spurious center-of-mass motion shifts the 1$^-_1$ level significantly, improving agreement with experiment.
Exotic neutron-rich medium-mass nuclei with realistic nuclear forces
Tsunoda, Naofumi; Shimizu, Noritaka; Hjorth-Jensen, Morten; Takayanagi, Kazuo; Suzuki, Toshio
2016-01-01
We present the first application of the newly developed theory of effective nucleon-nucleon interactions to the structure of exotic nuclei. This theory, a novel revision of many-body perturbation theory, enables us to perform shell-model calculations with several major shells ({\\it e.g.} $sd$+$pf$). Using the Entem-Machleidt QCD-based $\\chi\\mathrm{N}^3\\mathrm{LO}$ interaction and the Fujita-Miyazawa three-body force, exotic neutron-rich Ne, Mg and Si isotopes are studied systematically, with a good description of ground-state energies, 2$_1^+$ and 4$_1^+$ levels, and E2 transitions, as the first shell-model calculation for the "island of inversion" without two-body matrix elements fitted to experiment. The drip lines are predicted. We show effective single-particle energies from this interaction, exhibiting the shell evolution produced by the $\\chi\\mathrm{N}^3\\mathrm{LO}$ interaction + three-body force. The doubly-magic structure of ${}^{34}\\mathrm{Si}$ is demonstrated.
Characterization of the low-lying 0$^{+}$ and 2$^{+}$ states of $^{68}$ Ni
Recently, a number of low-lying low-spin states have been firmly identified in $^{68}$Ni; the position of the first excited state (which is a 0$^{+}$ state), the spin and parity of the second excited 0$^{+}$ state and the spin and parity of the second and third 2$^+$ states have been fixed. The identification of these three pairs of 0$^+$ and 2$^+$ states in $^{68}$Ni (Z=28 and N=40) forms ideal tests to validate shell-model calculations and the effective interactions developed for the nickel region but also hints to triple shape coexistence including even strongly deformed structures. The aim of this proposal is to collect detailed spectroscopic data of the low-spin states of $^{68}$Ni (Z=28, N=40) in order to characterize these triple pairs of 0$^+$ and 2$^+$ states. $\\gamma$-branching ratios of the 0$^+$ and 2$^+$ states and the E0 transition strengths as well as the E2 transition rate of the 0$_3^+$ will be obtained using the new ISOLDE decay station that is constructed from an efficient array of germaniu...
Observation of electric quadrupole X-ray transitions in muonic thallium, lead and bismuth
Schneuwly, H; Engfer, R; Jahnke, U; Kankeleit, E; Lindenberger, K H; Pearce, R M; Petitjean, C; Schellenberg, L; Schröder, W U; Walter, H K; Zehnder, A
1972-01-01
Electric quadrupole X-ray transitions (5g to 3d, 4f to 2p, and 3d to 1s) have been observed in muonic Tl, Pb and Bi. From the 3 to 1 transitions, energy splittings of the n=3 levels were deduced. From a comparison of the relative intensities of E1 and E2 transitions the population ratios 5g/5f, 4f/4d, and 3d/3p were deduced. These ratios are well reproduced by a cascade calculation assuming a statistical initial population at n=20, including K, L and M shell conversion. In the case of /sup 205/Tl discrepancies between the experimental and the calculated 3d-1s/3p-is intensity ratio can be explained by nuclear excitation. From the 3p/sub 3/2/ to 1s/sub 1/2/ intensity in /sup 209 /Bi one can deduce the ratio of the radiationless to the X-ray transition width and give limits for prompt neutron emission from the 3d level. (23 refs).
Sequence of Potentials Interpolating between the U(5) and E(5) Symmetries
Bonatsos, D; Minkov, N; Raychev, P P; Terziev, P A; Bonatsos, Dennis
2004-01-01
It is proved that the potentials of the form $\\beta^{2n}$ (with $n$ being integer) provide a ``bridge'' between the U(5) symmetry of the Bohr Hamiltonian with a harmonic oscillator potential (occuring for $n=1$) and the E(5) model of Iachello (Bohr Hamiltonian with an infinite well potential, materialized for infinite $n$). Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are given for the potentials $\\beta^4$, $\\beta^6$, $\\beta^8$, corresponding to $R_4=E(4)/E(2)$ ratios of 2.093, 2.135, 2.157 respectively, compared to the $R_4$ ratios 2.000 of U(5) and 2.199 of E(5). Hints about nuclei showing this behaviour, as well as about potentials ``bridging'' the E(5) symmetry with O(6) are briefly discussed. A note about the appearance of Bessel functions in the framework of E(n) symmetries is given as a by-product.
Sequence of Potentials Lying Between the U(5) and X(5) Symmetries
Bonatsos, D; Minkov, N; Raychev, P P; Terziev, P A; Bonatsos, Dennis
2004-01-01
Starting from the original collective Hamiltonian of Bohr and separating the beta and gamma variables as in the X(5) model of Iachello, an exactly soluble model corresponding to a harmonic oscillator potential in the beta-variable (to be called X(5)-$\\beta^2$) is constructed. Furthermore, it is proved that the potentials of the form $\\beta^{2n}$ (with n being integer) provide a ``bridge'' between this new X(5)-$\\beta^2$ model (occuring for n=1) and the X(5) model (corresponding to an infinite well potential in the beta-variable, materialized for n going to infinity. Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are given for the potentials $\\beta^2$, $\\beta^4$, $\\beta^6$, $\\beta^8$, corresponding to E(4)/E(2) ratios of 2.646, 2.769, 2.824, and 2.852 respectively, compared to the E(4)/E(2) ratios of 2.000 for U(5) and 2.904 for X(5). Hints about nuclei showing this behaviour, as well as about potentials ``bridging'' the X(5) symmetry with SU(3) are briefly disc...
Measurement of an atomic quadrupole moment using dynamic decoupling
Akerman, Nitzan; Shaniv, Ravid; Ozeri, Roee
2016-05-01
Some of the best clocks today are ion-based optical clocks. These clocks are referenced to a narrow optical transition in a trapped ion. An example for such a narrow transition is the electric quadrupole E 2 transition between states with identical parity. An important systematic shift of such a transition is the quadrupole shift resulting from the electric field gradient inherent to the ion trap. We present a new dynamic decoupling method that rejects magnetic field noise while measuring the small quadrupole shift of the optical clock transition. Using our sequence we measured the quadrupole moment of the 4D5/2 level in a trapped 88 Sr+ ion to be 2 .973-0 . 033 + 0 . 026 ea02 , where e is the electron charge and a0 is the Bohr radius. Our measurement improves the uncertainty of this value by an order of magnitude and thus helps mitigate an important systematic uncertainty in 88 Sr+ based optical atomic clocks and verifies complicated many-body quantum calculations.
Microscopic study of neutron-rich dysprosium isotopes
Energy Technology Data Exchange (ETDEWEB)
Vargas, Carlos E. [Universidad Veracruzana, Facultad de Fisica e Inteligencia Artificial, Xalapa (Mexico); Universidad Nacional Autonoma de Mexico, Facultad de Ciencias, Apartado Postal 70-542, Mexico D.F. (Mexico); Velazquez, Victor [Universidad Nacional Autonoma de Mexico, Facultad de Ciencias, Apartado Postal 70-542, Mexico D.F. (Mexico); Lerma, Sergio [Universidad Veracruzana, Facultad de Fisica e Inteligencia Artificial, Xalapa (Mexico)
2013-01-15
Microscopic studies in heavy nuclei are very scarce due to large valence spaces involved. This computational problem can be avoided by means of the use of symmetry-based models. Ground-state, {gamma} and {beta} bands, and their B(E2) transition strengths in {sup 160-168}Dy isotopes, are studied in the framework of the pseudo-SU(3) model which includes the preserving symmetry Q . Q term and the symmetry-breaking Nilsson and pairing terms, systematically parametrized. Additionally, three rotor-like terms are considered, whose free parameters, fixed for all members of the chain, are used to fine tune the moment of inertia of rotational bands and the band head of {gamma} and {beta} bands. The model succesfully describes in a systematic way rotational features in these nuclei and allows to extrapolate toward the midshell nucleus {sup 170}Dy. The results presented show that it is possible to study a full chain of isotopes or isotones in the region with the present model. (orig.)
Levels of 232U fed in 236Pu α decay
Ardisson, G.; Hussonnois, M.; Ledu, J. F.; Trubert, D.; Lederer, C. M.
1994-06-01
The γ spectrum following the α decay of 236Pu has been reinvestigated with a high-resolution HPGe detector. Accurate energies and intensities are reported for 26 γ transitions, of which 20 were observed for the first time. A decay scheme is constructed using the Ritz combination principle, γγ coincidence data, and previously known data from nuclear reactions and from232Pa β- decay. We observe feeding of the ground-state rotational band up to spin 8, the β vibrational band to spin 4, the K=0 octupole vibrational band to spin 5, and the bandhead of the γ vibrational band. New states of 232U at 927.3 and 967.7 keV, populated with low α-decay hindrance factors, are assigned as members of a second-excited Kπ=0+ band. The ratio of E1/E2 transitions in the decay of these states suggests that the E1 transitions to members of the K=0 octupole band may be rather fast (~=10-3 Weisskopf units). Systematics of hindrance factors for α decay to vibrational states are presented.
The Kuo-Brown effective interaction: From 18O to the Sn isotopes
Engeland, Torgeir; Hjorth-Jensen, Morten; Kartamyshev, Maxim; Osnes, Eivind
2014-08-01
After briefly reviewing the pioneering work on effective interactions by Gerry Brown and his group, and the developments which followed, we apply present-day effective interactions to large-scale shell-model calculations on the entire range of Sn isotopes from 102Sn to 132Sn. We have made explorative calculations starting from three different nucleon-nucleon potentials (Argonne V18, CD-Bonn, and N3LO) and evaluated the higher-order contributions to the effective interaction from both G-matrix and Vlowk interactions. Further, we have checked the convergence of intermediate-state excitations up to 10ħω harmonic oscillator energy. Final extensive calculations were made of binding energies, excitation energies and B(E2) transition rates using an effective interaction based on a G-matrix evaluated from the chiral N3LO potential and including intermediate excitations up to 10ħω harmonic oscillator energy. The energy spectra are well reproduced throughout the region while overbinding of the ground states emerges as valence nucleons are added. The B(E2) rates agree well for the heavy isotopes, while they seem too low for the lighter ones.
Atomic parity violation in a single trapped radium ion
Energy Technology Data Exchange (ETDEWEB)
Versolato, O. O., E-mail: versolato@kvi.nl; Wansbeek, L. W.; Giri, G. S.; Berg, J. E. van den; Hoek, D. J. van der; Jungmann, K.; Kruithof, W. L.; Onderwater, C. J. G.; Sahoo, B. K.; Santra, B.; Shidling, P. D.; Timmermans, R. G. E.; Willmann, L.; Wilschut, H. W. [University of Groningen, Kernfysisch Versneller Instituut (Netherlands)
2011-07-15
Atomic parity violation (APV) experiments are sensitive probes of the electroweak interaction at low energy. These experiments are competitive with and complementary to high-energy collider experiments. The APV signal is strongly enhanced in heavy atoms and it is measurable by exciting suppressed (M1, E2) transitions. The status of APV experiments and theory are reviewed as well as the prospects of an APV experiment using one single trapped Ra{sup + } ion. The predicted enhancement factor of the APV effect in Ra{sup + } is about 50 times larger than in Cs atoms. However, certain spectroscopic information on Ra{sup + } needed to constrain the required atomic many-body theory, was lacking. Using the AGOR cyclotron and the TRI{mu}P facility at KVI in Groningen, short-lived {sup 212 - 214}Ra{sup + } ions were produced and trapped. First ever excited-state laser spectroscopy was performed on the trapped ions. These measurements provide a benchmark for the atomic theory required to extract the electroweak mixing angle to sub-1% accuracy and are an important step towards an APV experiment in a single trapped Ra{sup + } ion.
Symmetries of Quadrupole-Collective Vibrational Motion in Transitional Even-Even 124−134Xenon Nuclei
Pietralla, N; Rainovski, G; Ahn, T; Bauer, C; Leske, J; Möller, O; Möller, T
2010-01-01
Projectile-Coulomb excitation of Xe isotopes has been performed at ANL using the Gammasphere array for the detection of γ-rays. The one-quadrupole phonon 2+ 1,ms mixed-symmetry state (MSS) has been traced in the stable N=80 isotones down to 134Xe. First, the data on absolute E2 andM1 transition rates quantify the amount of F-spin symmetry in these nuclei and provide a new local measure for the pn-QQ interaction. Second, the evolution of the 2+ 1,ms state has been studied along the sequence of stable even-even 124−134Xe isotopes that are considered to form a shape transition path from vibrational nuclei with vibrational U(5) symmetry near N=82 to γ-softly deformed shapes with almost O(6) symmetry. Third, our data on more than 50 absolute E2 transition rates between off-yrast low-spin states of 124,126Xe enable us to quantitatively test O(6) symmetry in these nuclei. As a result we find that O(6) symmetry is more strongly broken in the A=130 mass region than previously thought. The data will be discussed.
Weak nuclear collectivity from proton and neutron pairing gaps
Orce, Nico
2010-01-01
I explore weakly-collective singly-closed shell nuclei with high-j shells where active valence neutrons and particle-particle correlations may be the dominant collective degree of freedom. The combination of large and close-lying proton and neutron pairing gaps extracted from experimental masses seems to charaterize the origin of the weak collectivity observed in Ni and Sn superfluids with $N\\approx Z$. The trend of $E2$ transition strengths, i.e., $B(E2; 2^+_1\\rightarrow 0^+_1)$ values, in these nuclei is predicted from proton and neutron pairing-gap information. The agreement with the Ni isotopes is excellent and recent experimental results support the trend in the Sn isotopes. This work emphasizes the importance of atomic masses in elucidating nuclear-structure properties. In particular, it indicates that many-body microscopic properties such as nuclear collectivity could be directly inferred from more macroscopic average properties such as atomic masses.
Dispersion amplitudes in the Moessbauer lineshape of /sup 237/Np, /sup 182/W, and /sup 195/Pt
Energy Technology Data Exchange (ETDEWEB)
Potzel, W. (Technische Universitaet Muenchen, Garching, Ger.); Wagner, F.E.; Kalvius, G.M.; Asch, L.; Spirlet, J.C.; Mueller, W.
1977-01-01
Measurements of the dispersion amplitude for the Moessbauer resonances in /sup 237/Np (60 keV), /sup 182/W (100 keV) and /sup 195/Pt (99 keV) are reported. For the E1 transition in /sup 237/Np a value of xi = -(3.4 + 0.2) x 10/sup -2/ was found. Theoretical estimates of xi for this case are of limited accuracy and the comparison with experimental data is inaccurate because of the considerable line broadening. Computer simulations show the influence of xi on /sup 237/Np hyperfine spectra. For the E2 transition in /sup 182/W the dependence of the effective value of xi on absorber thickness was studied. Extrapolations to zero thickness yield xi = -(1.0 +- 0.1) x 10/sup -2/ in good agreement with theoretical calculations. For /sup 195/Pt we found xi = -(1.1 +- 0.3) x 10/sup -2/ for the dispersion amplitude at zero absorber thickness. This is the first pure M1 transition for which a dispersion term has been observed. For all three resonances the dispersion is large enough to affect the determination of isomer shifts.
Lifetime measurements in $^{63}$Co and $^{65}$Co
Dijon, A; De France, G; Van Isacker, P; Ljungvall, J; Görgen, A; Obertelli, A; Korten, W; Gadea, A; Gaudefroy, L; Hackstein, M; Mengoni, D; Pissulla, Th; Recchia, F; Rejmund, M; Rother, W; Sahin, E; Schmitt, C; Shrivastava, A; Valiente-Dobon, J J; Zell, K O; Zielinska, M
2011-01-01
Lifetimes of the $9/2^-_1$ and $3/2^-_1$ states in $^{63}$Co and the $9/2^-_1$ state in $^{65}$Co were measured using the recoil distance Doppler shift and the differential decay curve methods. The nuclei were populated by multi-nucleon transfer reactions in inverse kinematics. Gamma rays were measured with the EXOGAM Ge array and the recoiling fragments were fully identified using the large-acceptance VAMOS spectrometer. The E2 transition probabilities from the $3/2^-_1$ and $9/2^-_1$ states to the $7/2^-$ ground state could be extracted in $^{63}$Co as well as an upper limit for the $9/2^-_1\\rightarrow7/2^-_1$ $B$(E2) value in $^{65}$Co. The experimental results were compared to large-scale shell-model calculations in the $pf$ and $pfg_{9/2}$ model spaces, allowing to draw conclusions on the single-particle or collective nature of the various states.
Doping and strain dependence of the electronic band structure in Ge and GeSn alloys
Xu, Chi; Gallagher, James; Senaratne, Charutha; Brown, Christopher; Fernando, Nalin; Zollner, Stefan; Kouvetakis, John; Menendez, Jose
2015-03-01
A systematic study of the effect of dopants and strain on the electronic structure of Ge and GeSn alloys is presented. Samples were grown by UHV-CVD on Ge-buffered Si using Ge3H8 and SnD4 as the sources of Ge and Sn, and B2H6/P(GeH3)3 as dopants. High-energy critical points in the joint-density of electronic states were studied using spectroscopic ellipsometry, which yields detailed information on the strain and doping dependence of the so-called E1, E1 +Δ1 , E0' and E2 transitions. The corresponding dependencies of the lowest direct band gap E0 and the fundamental indirect band gap Eindwere studied via room-T photoluminescence spectroscopy. Of particular interest for this work were the determination of deformation potentials, band gap renormalization effects, Burstein-Moss shifts due to the presence of carriers at band minima, and the dependence of other critical point parameters, such as amplitudes and phase angles, on the doping concentration. The selective blocking of transitions due to high doping makes it possible to investigate the precise k-space location of critical points. These studies are complemented with detailed band-structure calculations within a full-zone k-dot- p approach. Supported by AFOSR under DOD AFOSR FA9550-12-1-0208 and DOD AFOSR FA9550-13-1-0022.
Zhang, Xilin; Miller, Gerald A.
2017-01-01
Recently, the experimentalists in [Phys.Rev.Lett.116.042501(2016)] claimed seeing unexpected enhancement of the internal electron-positron pair (e+-e-) production in the large e+-e- relative angle region in the EM transition from the Beryllium-8 nucleus's second lowest 1+ state to its ground state. According to the experimentalists, the signal can be explained by a new neutral boson weighted around 17 MeV. This has stipulated significant interests in the particle physics community [e.g. Phys. Rev. Lett. 117, 071803 (2016)]. In this talk, I will present our latest study of the underlying nuclear physics, and emphasize several pieces of physics that haven't been well studied theoretically and not been included in the current experimental analysis, including the interferences between the dominant E1 and M1 transitions, two extra angular dependences, possible impact of E2 transition and its interferences with E1 and M1, and nuclear form factor. I will also point out that the previously measured on-shell photon production constrains the ratio between E1 and M1 contributions in the pair production, which however haven't been checked in the current experimental analysis. In the end, I will discuss the possibility of nuclear physics being the origin of the observed anomaly. The work is supported by the U.S. Department of Energy under Grant DE-FG02-97ER-41014.
Nomura, K; Robledo, L M
2016-01-01
The structure of even-even neutron-rich Ru, Mo, Zr and Sr nuclei in the $A\\approx 100$ mass region is studied within the interacting boson model (IBM) with microscopic input from the self-consistent mean-field approximation based on the Gogny-D1M energy density functional. The deformation energy surface in the quadrupole deformation space $(\\beta,\\gamma)$, computed within the constrained Hartree-Fock-Bogoliubov framework, is mapped onto the expectation value of the appropriately chosen IBM Hamiltonian with configuration mixing in the boson condensate state. The mapped IBM Hamiltonian is used to study the spectroscopic properties of $^{98-114}$Ru, $^{96-112}$Mo, $^{94-110}$Zr and $^{92-108}$Sr. Several cases of $\\gamma$-soft behavior are predicted in Ru and Mo nuclei while a pronounced coexistence between strongly-prolate and weakly-oblate deformed shapes is found for Zr and Sr nuclei. The method describes well the evolution of experimental yrast and non-yrast states as well as selected $B$(E2) transition prob...
Signatures of shape phase transitions in odd-mass nuclei
Nomura, K.; Nikšić, T.; Vretenar, D.
2016-12-01
Quantum phase transitions between competing ground-state shapes of atomic nuclei with an odd number of protons or neutrons are investigated in a microscopic framework based on nuclear energy density functional theory and the particle-plus-boson-core coupling scheme. The boson-core Hamiltonian, as well as the single-particle energies and occupation probabilities of the unpaired nucleon, are completely determined by constrained self-consistent mean-field calculations for a specific choice of the energy density functional and paring interaction, and only the strength parameters of the particle-core coupling are adjusted to reproduce selected spectroscopic properties of the odd-mass system. We apply this method to odd-A Eu and Sm isotopes with neutron number N ≈90 , and explore the influence of the single unpaired fermion on the occurrence of a shape phase transition. Collective wave functions of low-energy states are used to compute quantities that can be related to quantum order parameters: deformations, excitation energies, E 2 transition rates, and separation energies, and their evolution with the control parameter (neutron number) is analyzed.
Quasi-SU(3) truncation scheme for even-even sd-shell nuclei
Vargas, C E; Draayer, J P
2000-01-01
The Quasi-SU(3) symmetry was uncovered in full pf and sdg shell-model calculations for both even-even and odd-even nuclei. It manifests itself through a dominance of single-particle and quadrupole-quadrupole terms in the Hamiltonian used to describe well-deformed nuclei. A practical consequence of the quasi-SU(3) symmetry is an efficient basis truncation scheme. In a recent work was shown that when this type of Hamiltonian is diagonalized in an SU(3) basis, only a few irreducible represntations (irreps) of SU(3) are needed to describe the Yrast band, the leading S = 0 irrep augmented with the leading S = 1 irreps in the proton and neutron subspaces. In the present article the quasi-SU(3) truncation scheme is used, in conjunction with a "realistic but schematic" Hamiltonian that includes the most important multipole terms, to describe the energy spectra and B(E2) transition strengths of 20-Ne, 22-Ne, 24-Mg and 28-Si. The effect of the size of the Hilbert space on both sets of observables is discussed, as well ...
Dong, G X; Fossez, K; Płoszajczak, M; Jaganathen, Y; Betan, R M Id
2016-01-01
According to standard stellar evolution, lithium abundance is believed to be a useful indicator of the stellar age. However, many evolved stars like red giants show huge fluctuations around expected theoretical abundances that are not yet fully understood. The better knowledge of nuclear reactions that contribute to the creation and destruction of lithium can help to solve this puzzle. In this work we apply the Gamow shell model (GSM) formulated in the coupled-channel representation (GSM-CC) to investigate the mirror radiative capture reactions $^6$Li$(p,\\gamma)$$^7$Be and $^6$Li$(n,\\gamma)$$^7$Li. The cross-sections are calculated using a translationally invariant Hamiltonian with the finite-range interaction which is adjusted to reproduce spectra, binding energies and one-nucleon separation energies in $^{6-7}$Li, $^7$Be. All relevant $E1$, $M1$, and $E2$ transitions from the initial continuum states to the final bound states $J={3/2}_1^-$ and $J={1/2}^-$ of $^7$Li and $^7$Be are included. We demonstrate th...
H2+ and HD+: candidates for a molecular clock
Karr, Jean-Philippe
2014-01-01
We investigate the leading systematic effects in ro-vibrational spectroscopy of the molecular hydrogen ions H2+ and HD+, in order to assess their potential for the realization of optical clocks that would be sensitive to possible variations of the proton-to-electron mass ratio. Both two-photon (2E1) and quadrupole (E2) transitions are considered. In view of the weakness of these transitions, most attention is devoted to the light shift induced by the probe laser, which we express as a function of the transition amplitude, differential dynamic polarizability and clock interrogation times. Transition amplitudes and dynamic polarizabilites including the effect of hyperfine structure are then calculated in a full three-body approach to get a precise evaluation of the light shift. Together with the quadrupole and Zeeman shifts that are obtained from previous works, these results provide a realistic estimate of the achievable accuracy. We show that the lightshift is the main limiting factor in the case of two-photo...
Description of the shape coexistence in neutron-deficient 74,76Kr with IBM2
Zhang, DaLi; Mu, ChengFu
2016-08-01
The shape deformation and shape coexistence in 74,76Kr isotopes are investigated within the framework of the proton-neutron interacting boson model (IBM2). By considering the relative energy of the d proton boson to be different from that of the neutron boson, the low-lying energy spectrum is in good agreement with experimental results both qualitatively and quantitatively. In particular, the low-lying 0 2 + states associated with the shape-coexistence phenomenon are reproduced quite well. The calculated key sensitive quantities of B(E2) transition branch ratios are fairly consistent with the experimental data except for R 4. The predicated deformation parameter is very similar for the ground states in 74Kr and 76Kr, showing good agreement with the experimental result, and the calculated deformation parameter for the second 0+ state in 74Kr is close to the experimental data. The calculated results of the triaxiality parameter indicated an almost purely prolate shape for the ground state of 76Kr and a mostly prolate shape with a little triaxiality for the ground state of 74Kr. The calculations also show an oblate triaxial shape for the second 0+ state in 76Kr and maximum triaxiality for the second 0+ state in 74Kr. These results confirm the importance of the triaxial deformation for the description of such shape coexistence.
Relativistic Coulomb excitation of {sup 88}Kr
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Moschner, Kevin; Blazhev, Andrey; Jolie, Jan; Warr, Nigel; Wendt, Andreas [IKP, Universitaet zu Koeln, 50937 Koeln (Germany); Collaboration: PreSPEC-Collaboration
2015-07-01
Within the scope of the PreSPEC campaign we performed a Coulomb-excitation experiment to determine absolute E2 transition strengths to 2{sup +} states in the radioactive nucleus {sup 88}Kr. The aim of our studies was to identify the one quadruple-phonon mixed-symmetry 2{sub MS}{sup +} state in order to extend our knowledge on these states to lighter N = 52 isotones and to track their evolution over different proton shells. The investigated ions were provided through projectile fission of a 650 MeV {sup 238}U beam on a primary target consisting of 0.6 g/cm{sup 2} {sup 9}Be and subsequent separation and identification of the reaction products via the FRS at GSI. The secondary target consisted of 0.4 g/cm{sup 2} {sup 197}Au. De-exciting γ radiation was detected by the PreSPEC array, consisting of 15 EUROBALL Cluster detectors. The Lund-York-Cologne-CAlorimeter LYCCA was used for particle identification after the secondary target. Absolute transition strengths of the transitions depopulating the 2{sup +}{sub 3} state in {sup 88}Kr which suggest the mixed symmetric character of this state are presented and discussed within the systematics of the N = 52 isotones.
Effective field theory for vibrations in odd-mass nuclei
Pérez, E A Coello
2016-01-01
Heavy even-even nuclei exhibit low-energy collective excitations that are separated in scale from the microscopic (fermion) degrees of freedom. This separation of scale allows us to approach nuclear vibrations within an effective field theory (EFT). In odd-mass nuclei collective and single-particle properties compete at low energies, and this makes their description more challenging. In this article we describe odd-mass nuclei with ground-state spin $I=\\sfrac{1}{2}$ by means of an EFT that couples a fermion to the collective degrees of freedom of an even-even core. The EFT relates observables such as energy levels, electric quadrupole ($E2$) transition strengths, and magnetic dipole ($M1$) moments of the odd-mass nucleus to those of its even-even neighbor, and allows us to quantify theoretical uncertainties. For isotopes of rhodium and silver the theoretical description is consistent with data within experimental and theoretical uncertainties. Several testable predictions are made.
Microscopic study of neutron-rich Dysprosium isotopes
Vargas, Carlos E; Lerma, Sergio; 10.1140/epja/i2013-13004-1
2013-01-01
Microscopic studies in heavy nuclei are very scarce due to large valence spaces involved. This computational problem can be avoided by means of the use of symmetry based models. Ground-state, gamma and beta-bands, and their B(E2) transition strengths in 160-168Dy isotopes, are studied in the framework of the pseudo-SU(3) model which includes the preserving symmetry Q.Q term and the symmetry-breaking Nilsson and pairing terms, systematically parametrized. Additionally, three rotor-like terms are considered whose free parameters, fixed for all members of the chain are used to fine tune the moment of inertia of rotational bands and the band-head of gamma and beta-bands. The model succesfully describes in a systematic way rotational features in these nuclei and allows to extrapolate toward the midshell nucleus 170Dy. The results presented show that it is possible to study full chain of isotopes or isotones in the region with the present model.
Finding the Missing γ in D+Darrow ^4He Cold Fusion Excess Heat:
Chubb, Scott
2002-03-01
The source of Cold Fusion (CF)Excess Heat is a novel form of D+Darrow ^4He reaction in which no high energy γ rays are emitted (http:// www.aps.org/meet/MAR01/baps/abs/S7640003.html) . An important source of confusion concerning this point is the apparent lack of consensus about known effects associated even with the conventional D+Darrow^4He+γ reaction. In fact, although little information about D+Darrow ^4He+γ appears in the conventional fusion literature, the photo-dissociation reaction ^4He+γarrowD+D not only has been widely studied but is known to occur through a quadrupolar (E2) transition in which the two particle wave function associated with the D-nuclei is required to preserve Bose symmetry, in the far field regions, where the Electromagnetic Interaction EMI is dominant. Also in this reaction coupling occurs between strong and EMI's that invalidates the separability requirements that are present in the remaining D+D fusion reactions. These facts lend credibility to the notion that coherent many-body effects, involving D-exchange can alter the reaction in such a way that γ ray emission is not required.
Description of the neutron deficient Sr and Zr isotopes in the interacting boson model
Energy Technology Data Exchange (ETDEWEB)
Bucurescu, D.; Cata, G.; Cutoiu, D.; Constantinescu, G.; Ivascu, M.; Zamfir, N.V. (Institutul Central de Fizica, Bucharest (Romania))
1983-05-30
The available experimental data for the neutron deficient isotopes of Sr (78 to 86) and Zr (80 to 86) are collected and compared to the predictions of IBA-1 model calculations. The variations of the collectivity along these two isotopic chains is well reproduced with a set of smoothly varying parameters of the model. The description of both the energy levels and the B(E2) transition probabilities improves with decreasing N, the hamiltonian evolving towards an SU(3) dynamical symmetry. Both the large B(E2) value of the 2/sub 1//sup +/->0/sup +/sub(g.s.) transition and the predicted prolate shape for the very light isotopes, agree well with the recent findings of superdeformed nuclei around Z, N proportional 38. Transition strengths for the (p,t) reaction are calculated and compared to experimental observations for 0/sup +/ states, and a discussion is made about the possible intruder character of the O/sub 2//sup +/ state. The interacting boson-fermion approximation (IBFA) model is used to extend the calculations to some odd nuclei. Two shell (1gsub(9/2), 2dsub(5/2)) calculations are performed for the positive-parity states in /sup 83/Sr, /sup 81/Sr and /sup 85/Y and they compare well with the experimental level scheme of these nuclei below 3 MeV excitation.
Tursunov, E M; Turakulov, S A; Bray, I
2016-01-01
The astrophysical capture process $\\alpha+d$ $\\rightarrow$ $^6$Li + $\\gamma$ is studied in a three-body model. The initial state is factorized into the deuteron bound state and the $\\alpha+d$ scattering state. The final nucleus $^6$Li(1+) is described as a three-body bound state $\\alpha+n+p$ in the hyperspherical Lagrange-mesh method. The contribution of the E1 transition operator from the initial isosinglet states to the isotriplet components of the final state is estimated to be negligible. An estimation of the forbidden E1 transition to the isosinglet components of the final state is comparable with the corresponding results of the two-body model. However, the contribution of the E2 transition operator is found to be much smaller than the corresponding estimations of the two-body model. The three-body model perfectly matches the new experimental data of the LUNA collaboration with the help of the spectroscopic factor 2.586, very consistent with the three-body structure of the final state.
Theoretical study of the α +d →6Li +γ astrophysical capture process in a three-body model
Tursunov, E. M.; Kadyrov, A. S.; Turakulov, S. A.; Bray, I.
2016-07-01
The astrophysical capture process α +d →6Li is studied in a three-body model. The initial state is factorized into the deuteron bound state and the (α +d )-scattering state. The final nucleus 6Li (1+) is described as a three-body bound state α +n +p in the hyperspherical Lagrange-mesh method. The contribution of the E 1 -transition operator from the initial isosinglet states to the isotriplet components of the final state is estimated to be negligible. An estimation of the forbidden E 1 transition to the isosinglet components of the final state is comparable with the corresponding results of the two-body model. However, the contribution of the E 2 -transition operator is found to be much smaller than the corresponding estimations of the two-body model. The three-body model perfectly matches the new experimental data of the LUNA Collaboration with the spectroscopic factor of 2.586 estimated from the bound-state wave functions of 6Li and a deuteron.
Structure Shape Evolution in Lanthanide and Actinide Nuclei
Directory of Open Access Journals (Sweden)
Khalaf A. M.
2013-04-01
Full Text Available To give the characteristics of the evolution of the collectivity in even-even nuclei, we studied the behavior of the energy ratios R(4 / 2 and R(6 / 4. All chains of lanthanides begins as vibrational with R(4 / 2 near 2.0 and move towards rotational (R(4 / 2 3.33 as neutron number increases. A rabid jump in R(4 / 2 near N = 90 was seen. The plot of R(4 / 2 against Z shows not only the existence of a shape transitions but also the change in curvature in the data for N = 88 and 90, concave to convex. For intermedi- ate structure the slopes in E-GOS ( E over spin plots range between the vibrator and rotor extremes. The abnormal behavior of the two-neutron separation energies of our lanthanide nuclei as a function of neutron number around neutron number 90 is cal- culated. Nonlinear behavior is observed which indicate that shape phase transition is occurred in this region. The calculated reduced B(E2 transition probabilities of the low states of the ground state band in the nuclei 150 Nd / 152 Sm / 154 Gd / 156 Dy are analyzed and compared to the prediction of vibrational U(5 and rotational SU(3 limits of interacting boson model calculations.
Shell Model for Warm Rotating Nuclei
Matsuo, M; Vigezzi, E; Broglia, R A; Yoshida, K
1997-01-01
In order to provide a microscopic description of levels and E2 transitions in rapidly rotating nuclei with internal excitation energy up to a few MeV, use is made of a shell model which combines the cranked Nilsson mean-field and the residual surface delta two-body force. The damping of collective rotational motion is investigated in the case of a typical rare-earth nucleus, namely \\Yb. It is found that rotational damping sets in at around 0.8 MeV above the yrast line, and the levels which form rotational band structures are thus limited. We predict at a given rotational frequency existence of about 30 rotational bands of various lengths, in overall agreement with the experimental findings. The onset of the rotational damping proceeds quite gradually as a function of the internal excitation energy. The transition region extends up to around 2 MeV above yrast and it is characterized by the presence of scars of discrete rotational bands which extend over few spin values and stand out among the damped transition...
Wu, Xiao-Peng; Sun, Xiao-Ming; Wei, Xi-Guang; Ren, Yi; Wong, Ning-Bew; Li, Wai-Kee
2009-06-09
The reactivity order of 12 anions toward ethyl chloride has been investigated by using the G2(+) method, and the competitive E2 and SN2 reactions are discussed and compared. The reactions studied are X(-) + CH3CH2Cl → HX + CH2═CH2 + Cl(-) and X(-) + CH3CH2Cl → CH3CH2X + Cl(-), with X = F, Cl, Br, HO, HS, HSe, NH2 PH2, AsH2, CH3, SiH3, and GeH3. Our results indicate that there is no general and straightforward relationship between the overall barriers and the proton affinity (PA) of X(-); instead, discernible linear correlations only exist for the X's within the same group of the periodic table. Similar correlations are also found with the electronegativity of central atoms in X, deformation energy of the E2 transition state (TS), and the overall enthalpy of reaction. It is revealed that the electronegativity will significantly affect the barrier height, and a more electronegative X will stabilize the E2 and SN2 transition states. Multiple linear regression analysis shows that there is a reasonable linear correlation between E2 (or SN2) overall barriers and the linear combination of PA of X(-) and electronegativity of the central atom.
Nettey, Samuel; Swift, Christopher A; Joviliano, Renan; Noin, Diogo O; Gronert, Scott
2012-06-06
For a series of α and β substituted haloethanes and haloethenes, gas-phase experiments and computational modeling have been used to characterize their nucleophilic substitution and elimination reactions. Despite being less thermodynamically favorable, the vinylic eliminations have rate constants and computed barriers that are similar to those of analogous aliphatic eliminations. This is the result of the vinylic systems shifting to more E1(cb)-like transition states and exploiting the inherent greater acidity of vinylic hydrogens. In general, the α-substituents have a greater impact on the S(N)2 pathways and stabilize the transition states via field and polarizability effects. Substantial stabilization is also provided to the E2 transition states by the α-substituents, but they have surprisingly little impact on the geometries of the transition states of either pathway. The β-substituents generally lead to a strong bias toward elimination and greatly affect the synchronicity of the elimination (more E1(cb)-like) as well as its location on the reaction coordinate (early). The experimental and computational data are in good accord, and the full data set provides a comprehensive picture of substituent effects on solvent-free S(N)2 and E2 processes.
Tang, Chenjie; Shi, Junxia
2015-05-01
Effects of delta doping location and density on intersubband transitions in AlGaN/GaN step quantum wells for terahertz (THz) applications have been investigated by solving Schrödinger and Poisson equations self-consistently. It shows that delta doping near the GaN well/AlGaN step well interface causes a blue-shift, while delta doping in the barrier or near barrier/GaN well and barrier/step well interfaces cause a red-shift first and then a blue-shift with increasing doping density. The shifts are attributed to the combination of many body effect and internal field modulation effect, and can be more than 200% or 70% of the e1-e2 transition energy, as for blue-shift or red-shift, respectively. In addition, the influences of delta-doping location and density on the absorption coefficient are also investigated in detail. Delta doping at the middle of a layer is found much more desirable over uniform-doping in order to improve the absorption coefficient, especially in the step well.
Search for α + core states in even-even Cr isotopes
Souza, M. A.; Miyake, H.
2017-07-01
The α + core structure is investigated in even-even Cr isotopes from the viewpoint of the local potential model. The comparison of Q_{α}/A values for even-even Cr isotopes and even-even A = 46, 54, 56, 58 isobars indicates that 46Cr and 54Cr are the most favorable even-even Cr isotopes for the α + core configuration. The ground state bands of the two Cr isotopes are calculated through a local α + core potential containing a nuclear term with (1 + Gaussian) × (W.S. + W.S.3) shape. The calculated spectra give a very good description of most experimental 46Cr and 54Cr levels, including the 0+ bandheads. The reduced α-widths, rms intercluster separations and B( E2) transition rates are determined for the ground state bands. The calculations reproduce the order of magnitude of the available experimental B( E2) values without using effective charges, indicate that the low-spin members of the ground state bands present a stronger α-cluster character, and point out that the 46Cr ground state band has a significant degree of α-clustering in comparison with 44Ti . The volume integral per nucleon pair and rms radius obtained for the α + 50Ti potential are consistent with those reported previously in the analysis of α elastic scattering on 50Ti.
Decay spectroscopy of 160Sm: The lightest four-quasiparticle K isomer
Directory of Open Access Journals (Sweden)
Z. Patel
2016-02-01
Full Text Available The decay of a new four-quasiparticle isomeric state in 160Sm has been observed using γ-ray spectroscopy at the RIBF, RIKEN. The four-quasiparticle state is assigned a 2π⊗2ν π52−[532], π52+[413], ν52−[523], ν72+[633] configuration. The half-life of this (11+ state is measured to be 1.8(4 μs. The (11+ isomer decays into a rotational band structure, based on a (6− ν52−[523]⊗ν72+[633] bandhead, consistent with the gK−gR values. This decays to a (5− two-proton quasiparticle state, which in turn decays to the ground state band. Potential energy surface and blocked-BCS calculations were performed in the deformed midshell region around 160Sm. They reveal a significant influence from β6 deformation and that 160Sm is the best candidate for the lightest four-quasiparticle K isomer to exist in this region. The relationship between reduced hindrance and isomer excitation energy for E1 transitions from multiquasiparticle states is considered with the new data from 160Sm. The E1 data are found to agree with the existing relationship for E2 transitions.
Energy Technology Data Exchange (ETDEWEB)
Pastore, S. [University of South Carolina; Wiringa, Robert B. [ANL; Pieper, Steven C. [ANL; Schiavilla, Rocco [Old Dominion U., JLAB
2014-08-01
We report quantum Monte Carlo calculations of electromagnetic transitions in $^8$Be. The realistic Argonne $v_{18}$ two-nucleon and Illinois-7 three-nucleon potentials are used to generate the ground state and nine excited states, with energies that are in excellent agreement with experiment. A dozen $M1$ and eight $E2$ transition matrix elements between these states are then evaluated. The $E2$ matrix elements are computed only in impulse approximation, with those transitions from broad resonant states requiring special treatment. The $M1$ matrix elements include two-body meson-exchange currents derived from chiral effective field theory, which typically contribute 20--30\\% of the total expectation value. Many of the transitions are between isospin-mixed states; the calculations are performed for isospin-pure states and then combined with the empirical mixing coefficients to compare to experiment. In general, we find that transitions between states that have the same dominant spatial symmetry are in decent agreement with experiment, but those transitions between different spatial symmetries are often significantly underpredicted.
Large low-energy M1 strength for ^{56,57}Fe within the nuclear shell model.
Brown, B Alex; Larsen, A C
2014-12-19
A strong enhancement at low γ-ray energies has recently been discovered in the γ-ray strength function of ^{56,57}Fe. In this work, we have for the first time obtained theoretical γ decay spectra for states up to ≈8 MeV in excitation for ^{56,57}Fe. We find large B(M1) values for low γ-ray energies that provide an explanation for the experimental observations. The role of mixed E2 transitions for the low-energy enhancement is addressed theoretically for the first time, and it is found that they contribute a rather small fraction. Our calculations clearly show that the high-ℓ(=f) diagonal terms are most important for the strong low-energy M1 transitions. As such types of 0ℏω transitions are expected for all nuclei, our results indicate that a low-energy M1 enhancement should be present throughout the nuclear chart. This could have far-reaching consequences for our understanding of the M1 strength function at high excitation energies, with profound implications for astrophysical reaction rates.
NUSTART: A PC code for NUclear STructure And Radiative Transition analysis and supplementation
Energy Technology Data Exchange (ETDEWEB)
Larsen, G.L.; Gardner, D.G.; Gardner, M.A.
1990-10-01
NUSTART is a computer program for the IBM PC/At. It is designed for use with the nuclear reaction cross-section code STAPLUS, which is a STAPRE-based CRAY computer code that is being developed at Lawrence Livermore National Laboratory. The NUSTART code was developed to handle large sets of discrete nuclear levels and the multipole transitions among these levels; it operates in three modes. The Data File Error Analysis mode analyzes an existing STAPLUS input file containing the levels and their multipole transition branches for a number of physics and/or typographical errors. The Interactive Data File Generation mode allows the user to create input files of discrete levels and their branching fractions in the format required by STAPLUS, even though the user enters the information in the (different) format used by many people in the nuclear structure field. In the Branching Fractions Calculations mode, the discrete nuclear level set is read, and the multipole transitions among the levels are computed under one of two possible assumptions: (1) the levels have no collective character, or (2) the levels are all rotational band heads. Only E1, M1, and E2 transitions are considered, and the respective strength functions may be constants or, in the case of E1 transitions, the strength function may be energy dependent. The first option is used for nuclei closed shells; the bandhead option may be used to vary the E1, M1, and E2 strengths for interband transitions. K-quantum number selection rules may be invoked if desired. 19 refs.
Study of thermally excited nuclei through E1 and E2 decay from collective modes
Energy Technology Data Exchange (ETDEWEB)
Million, B.; Bracco, A.; Benzoni, G.; Leoni, S.; Camera, F.; Wieland, O. [Dipartimento di Fisica, Universita di Milano and INFN, via Celoria 16, 20133, Milano (Italy); Maj, A.; Kmiecik, M. [Niewodniczanski Institute of Nuclear Physics, 31-342, Krakow (Poland); Gadea, A. [Laboratori Nazionali di Legnaro, via Romea, Legnaro (Italy); Herskind, B. [The Niels Bohr Institute, Blegdamsvej 15-17, 2100, Copenhagen (Denmark)
2004-04-01
The nuclear system at the limit of excitation energy and angular momentum is here studied in the case of the superdeformed nucleus {sup 143}Eu using {gamma}-spectroscopy techniques. The data are based on a EUROBALL experiment using the reaction {sup 37}Cl+{sup 110}Pd{yields}{sup 143}Eu+4n. The influence of thermal energy on superdeformed configurations is investigated through the analysis of the quasi-continuum spectra formed by E2 transitions among states of excited rotational bands with energy extending up to 4-5 MeV above the yrast line. In particular, the effective lifetimes of the discrete rotational bands forming ridge structures in {gamma}-{gamma} coincidence matrices is measured by a Doppler Shift Attenuation Method. The deduced quadrupole deformation of Q{sub t} {approx}10 eb indicates that the nucleus maintains its collectivity with increasing excitation energy, supporting the superdeformed character of the excited nuclear rotation. The obtained number of superdeformed discrete bands forming the ridge structures is found in good agreement with microscopic cranked shell model calculations including the decay-out process into the lower deformation minimum. In addition, the nuclear properties at higher excitation energies are investigated through the E1 {gamma}-decay of the giant dipole resonance (GDR). It is found that the intensity of the superdeformed yrast and excited bands increases by a factor of approximately 1.6 when a coincidence with a high-energy {gamma}-ray is required, showing the importance of the E1 cooling in the feeding mechanism of the superdeformed states. (orig.)
The 2+ excitation of the Hoyle state
Directory of Open Access Journals (Sweden)
Khoa Dao T.
2016-01-01
Full Text Available To understand why the 2+ excitation of the Hoyle state was so difficult to observe in the direct reaction experiments with the 12C target, a detailed folding model + coupled-channel analysis of the inelastic α+12C scattering at Elab = 240 and 386 MeV has been done using the complex optical potential and inelastic scattering form factor obtained from the double-folding model using the nuclear transition densities predicted by the antisymmetrized molecular dynamics. With the complex strength of the density dependent nucleon-nucleon interaction fixed by the optical model description of the elastic α+12C scattering, the inelastic scattering form factor was fine tuned to the best coupled-channel description of the (α, α′ cross section measured for each excited state of 12C, and the corresponding isoscalar Eλ transition strength has been accurately determined. The present analysis of the (α, α′ data measured in the energy bins around Ex ≈ 10 MeV has unambiguously revealed the E2 transition strength that should be assigned to the 22+ state of 12C. A very weak transition strength B(E2; 01+ → 22+ ≈ 3 e2fm4 has been established, which is smaller than the E2 strength predicted for the transition from the Hoyle state to the 22+ state by at least two orders of magnitude. This is one of the main reasons why the direct excitation of the 22+ state of 12C has been difficult to observe in the experiments.
Zhang, Xiaomei; Liu, Xiaoting; Liang, Guiying; Li, Rui; Xu, Haifeng; Yan, Bing
2016-01-01
The potential energy curves (PECs) of the 22 Λ-S states of the phosphorus monoiodide (PI) molecule have been calculated at the level of MRCI+Q method with correlation-consistent quadruple-ζ quality basis set. The spectroscopic constants of the bound states are determined, which well reproduce the available measurements. The metastable a1Δ state has been reported for the first time, which lies between the X3Σ- and b1Σ+ states and have much deeper well than the ground state. The R-dependent spin-orbit (SO) matrix elements are calculated with the full-electron Breit-Pauli operator. Based on the SO matrix elements, the perturbations that the 23Π state may suffer from are analyzed in detail. The SOC effect makes the original Λ-S states split into 51 Ω states. In the zero-field splitting of the ground state X3Σ-, the spin-spin coupling contribution (2.23 cm-1) is found to be much smaller compared to the spin-orbit coupling contribution (50 cm-1). The avoided crossings between the Ω states lead to much shallower potential wells and the change of dissociation relationships of the states. The Ω-state wavefunctions are analyzed depending on their Λ-S compositions, showing the strong interactions among several quasidegenerate Λ-S states of the same total SO symmetry. The transition properties including electric dipole (E1), magnetic dipole (M1), and electric quadrupole (E2) transition moments (TMs), the Franck-Condon factors, the transition probabilities and the radiative lifetimes are computed for the transitions between Ω components of a1Δ and b1Σ+ states and ground state. The transition probabilities induced by the E1, E2, and M1 transitions are evaluated. The E2 makes little effect on transition probabilities. In contrast, the E1 transition makes the main contribution to the transition probability and the M1 transition also brings the influence that cannot be neglected. Finally, the radiative lifetimes are determined with the transition moments including E
Zhang, Xiaomei; Yan, Peiyuan; Li, Rui; Gai, Zhiqiang; Liang, Guiying; Xu, Haifeng; Yan, Bing
2016-09-01
Total 34 Λ-S states of the PCl molecule have been studied by using the multi-reference configuration interaction plus the Davidson correction (MRCI+Q) method with the correlation consistent quadruple-zeta quality basis set. These states are correlated to three dissociation limits P(4Su)+Cl(2Pu), P(2Du)+Cl(2Pu), and P(2Pu)+Cl(2Pu), respectively. The potential energy curves (PECs) of the Λ-S states have been calculated, from which the spectroscopic constants of the bound states are determined. The calculated spectroscopic results well reproduce the available measurements. The spin-orbit matrix elements between the Λ-S states have been calculated, which indicate that the perturbations exist in the interacting system 11Π-23Π and 11Π-23Σ-. And the excited a1Δ, b1Σ+, 21Σ+ states could be predissociated induced by the spin-orbit coupling (SOC) effect. The SOC calculation on the PCl molecule has been performed with the state interaction method. This is the first time that the SOC effect of the PCl has been studied theoretically. The SOC effect leads to the 34 Λ-S states split into the 74 Ω states. The ground state X3Σ- splits into the X3 Σ0-+ (X10+) and X3Σ1- (X21) states. For the zero-field splitting of the X3Σ- state, the spin-orbit contribution of 6 cm-1 is much larger than spin-spin contribution of 0.32 cm-1. Under the influence of the SOC effect, the spectroscopic results of the a1Δ and b1Σ+ states have very small changes, but the dissociation energies strongly decrease. The transition properties of PCl are also predicted, including the E1, M1, and E2 transition moments, the Franck-Condon factors, the transition probabilities, and the radiative lifetimes. For the transitions from a1Δ-X3Σ- and b1Σ+-X3Σ-, the transition probabilities are in order of AE1 > AM1 ≫ AE2. The lifetimes for the b1Σ+(v'=0) state are 4.87ms (E1) and 4.57 ms (E1+M1), in good agreement with the available experimental result of 4.9±0.8 ms.
Possible Deformed States in {sup 115}In and {sup 117}ln
Energy Technology Data Exchange (ETDEWEB)
Baecklin, A.; Fogelberg, B. [Inst. of Physics, Univ. of Uppsala (Sweden); Swedish Research Councils' Laboratory, Studsvik, Nykoeping (Sweden); Malmskog, S.G. [AB Atomenergi, Nykoeping (Sweden)
1967-01-15
Levels and transitions in {sup 115}In and {sup 117}In have been studied from the beta decay of 2.3-day {sup 115g}Cd and 2.5-h {sup 117g}Cd. Using a Ge(Li) detector and a double focussing beta spectrometer energies, intensities, conversion coefficients and multipolarities were obtained for the following transitions (energies in keV and multipolarities are given): {sup 115}In: 35.63 (97.0 % M1 + 3.0 % E2), 231.47 (E1), 260.80 (M1), 267, 336. 23 (M4 + < 5 % E5), 492. 4 (96 % El +4 % M2), 527.70 (E1). {sup 117}In: 71.0, 89.80 (E2 + < 20 % M1), 273.32 (M1, E2), 315.27 (M4 + < 7 % E2), 344.29 (E1), 434.12 (E1). Using the delayed coincidence technique, half lives were measured for 2 levels in {sup 115}In and for 3 levels in {sup 117}In. Energies, spins, parities and half lives are given for the following levels: In: 597.03, 3/2{sup -}; 828.39, 3/2{sup +}, 5.4 ns; 863.95, l/2{sup +} or 3/2{sup +}, 1.1 ns. {sup 117}In: 588.59, 3/2{sup -}; 0.20 ns; 659.56, 3/2{sup +}, 58.7 ns; 749.37, 1/2{sup +} or 3/2{sup +}, 4.3 ns. Reduced transition probabilities are given for several transitions in both nuclei. The E2 transition rates between the two excited positive parity states in both nuclei were found to be about 100 s. p. u. indicating a possible deformation of these states. The energy spacing and transition rates between these states can be well accounted for within the Nilsson model assuming the states to form a K = 1/2{sup +} rotational band. A deformation {delta} of about 0.20 is obtained for both nuclei.
Shell-model states with seniority $\nu =3$ , 5, and 7 in odd- $A$ neutron-rich Sn isotopes
Energy Technology Data Exchange (ETDEWEB)
Iskra, Ł. W. [Polish Academy of Sciences (PAS), Sopot (Poland); Broda, R. [Polish Academy of Sciences (PAS), Sopot (Poland); Janssens, R. V. F. [Argonne National Lab. (ANL), Argonne, IL (United States); Chiara, C. J. [Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Maryland, College Park, MD (United States); Carpenter, M. P. [Argonne National Lab. (ANL), Argonne, IL (United States); Fornal, B. [Polish Academy of Sciences (PAS), Sopot (Poland); Hoteling, N. [Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Maryland, College Park, MD (United States); Kondev, F. G. [Argonne National Lab. (ANL), Argonne, IL (United States); Królas, W. [Polish Academy of Sciences (PAS), Sopot (Poland); Lauritsen, T. [Argonne National Lab. (ANL), Argonne, IL (United States); Pawłat, T. [Polish Academy of Sciences (PAS), Sopot (Poland); Seweryniak, D. [Argonne National Lab. (ANL), Argonne, IL (United States); Stefanescu, I. [Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Maryland, College Park, MD (United States); Walters, W. B. [Univ. of Maryland, College Park, MD (United States); Wrzesiński, J. [Polish Academy of Sciences (PAS), Sopot (Poland); Zhu, S. [Argonne National Lab. (ANL), Argonne, IL (United States)
2016-01-01
found to reproduce the experimental level energies rather well. Nevertheless, some systematic deviations between calculated and experimental energies, especially for positive-parity states, point to the need to improve some of the two-body interactions used in calculations. The computed wave-function amplitudes provide for a fairly transparent interpretation of the observed level structures. The systematics of level energies over the broad A = 117–129 range of Sn isotopes displays a smooth decrease with mass A, and the observed regularity confirms most of the proposed spin-parity assignments. The systematics of the B(E2) reduced transition probabilities extracted for the 23/2+ and 19/2+ isomers is discussed with an emphasis on the close similarity of the observed A dependence with that of the E2 transition rates established for other ν=2, 3, and 4 isomers in the Sn isotopic chain.
Institute of Scientific and Technical Information of China (English)
张战军; 方向正; 桑建平; 刘庸
2001-01-01
Nuclear transition charge/current density operators are composed according to valence nucleon degrees of freedom. By using boson expansion technique, a microscopic theoretical method (BE method) about the transformation of the fermion density operators into boson density operators is established. Thus, calculations of the nuclear charge/current densities can be carried out in the boson state space by taking advantage of the eigenfunctions of the microscopic IBM. Associated with the formal theories of electron-nucleus scattering and nuclear electromagnetic transition, a microscopic approach, which can be used to study nuclear transition charge/current densities, various form factors, differential cross sections, reduced transition rates, electromagnetic multipole moments, g factors and so on, is built up. The preliminary results based on the microscopic sdIBM-2 has indicated that the physical quantities mentioned before can be described well in the framework of the microscopic approach. The preliminary calculations of spectrum, E2 transition boson structure functions (BSF) and transition charge density from 2+1 to 0+1 in 192Os are carried out in terms of the present approach in the frame of the microscopic sd IBM-2. It is found that a reasonable description of these physical quantities has been achieued.%从价核子自由度出发构造出核跃迁电荷/电流密度算符，采用Dyson玻色子展开技术给出了获取核玻色子形式跃迁电荷/电流密度有效算符的一种微观方法(BE方法). 利用微观相互作用玻色子模型(IBM)提供的波函数可在玻色子态空间中求出核跃迁电荷/电流密度，结合电子-核散射以及核电磁跃迁的形式理论，建立了可研究电子-核散射各种形状因子，微分散射截面以及核约化跃迁几率、电磁多极矩、核态g因子等物理量的理论方案. 在一种微观sdIBM-2框架下，结合现有理论方案，初步计算了192Os核的能谱、E2跃迁
Energy Technology Data Exchange (ETDEWEB)
Sheikh Obeid, Abdulrahman
2014-11-01
In the framework of this thesis electron scattering experiments on low-energy excitations of {sup 92}Zr and {sup 94}Zr were performed at the S-DALINAC in a momentum transfer range q=0.3-0.6 fm{sup -1}. The nature of one-phonon symmetric and mixed-symmetric 2{sup +} and 3{sup -} states of {sup 92}Zr was investigated by comparison with predictions of the quasi-particle phonon model (QPM). Theoretical (e,e') cross sections have been calculated within the distorted wave Born approximation (DWBA) to account for Coulomb distortion effects. The reduced strengths of the one-quadrupole phonon states and the one-octupole phonon state have been extracted. The similarity of the momentum-transfer dependence of the form factors between the 2{sup +} states supports the one-phonon nature of the 2{sup +}{sub 2} state of {sup 92}Zr. A new method based on the Plane Wave Born Approximation (PWBA) for a model-independent determination of the ratio of the E2 transition strengths of fully symmetric (FSS) and mixed-symmetry (MSS) one-phonon excitations of heavy vibrational nuclei is introduced. Due to the sensitivity of electron scattering to charge distributions, the charge transition-radii difference can be determined. The basic assumptions (independence from the ratio of Coulomb corrections and from absolute values of transition radii) are tested within the Tassie model, which makes no specific assumptions about the structure of the states other than collectivity. It is shown that a PWBA analysis of the form factors, which usually fails for heavy nuclei, can nevertheless be applied in a relative analysis. This is a new promising approach to determine the ground state transition strength of the 2{sup +} MSS of vibrational nuclei with a precision limited only by the experimental information about the B(E2;2{sup +}{sub 1}→0{sup +}{sub 1}) strength. The PWBA approach furthermore provides information about differences of the proton transition radii of the respective states
A study of the single neutron knockout reaction from silicon-26 and sulfur-30
Reynolds, Robert R., Jr.
evidence in the current work, intermediate-energy Coulomb excitation studies would help in completing the level schemes and also verify the branching strength of the E2 transitions characteristic of deformed nuclei.