Backbends in directed percolation
Roy, R.; Sarkar, A.; White, D. G.
2001-01-01
When directed percolation in a bond percolation process does not occur any path to innity on the open bonds will zigzag back and forth through the lattice Backbends are the portions of the zigzags that go against the percolation direction They are important in the physical problem of particle transport in random media in the presence of a eld as they act to limit particle ow through the medium The critical probability for percolation along directed paths with backbends no longer than a given ...
Influence of quadrupole pairing on backbending
The backbending phenomenon is attributed to the Coriolis antipairing and the rotational alignment effects. We can consider both effects simultaneously by applying the cranked Hartree-Fock-Bogoliubov theory to the description of the rotational motion of nuclei. In usual treatments of the backbending, however, only the monopole pairing force is considered and pairing forces of other types are neglected. This may be the main reason for starting of the backbending at too small total angular momentum in theoretical results. (orig.)
Quasi-dynamical symmetries in the backbending of chromium isotopes
Herrera, Raul A.; Johnson, Calvin W.
2016-01-01
We examine the well-known backbending, or abrupt change in the moment of inertia along the yrast line, in $^{48,49,50}$Cr by decomposing configuration-interaction shell-model wavefunctions into group irreps, using the subgroups $L$ (total orbital angular momentum) and $S$ (total spin) of SU(2), and the groups SU(3) and SU(4). We see strong signatures of quasi-dynamical symmetries--the same or similar decomposition across members of a band--below the backbending, while quasi-dynamical symmetry...
Quasi-dynamical symmetries in the backbending of chromium isotopes
Herrera, Raul A
2016-01-01
We examine the well-known backbending, or abrupt change in the moment of inertia along the yrast line, in $^{48,49,50}$Cr by decomposing configuration-interaction shell-model wavefunctions into group irreps, using the subgroups $L$ (total orbital angular momentum) and $S$ (total spin) of SU(2), and the groups SU(3) and SU(4). We see strong signatures of quasi-dynamical symmetries--the same or similar decomposition across members of a band--below the backbending, while quasi-dynamical symmetry is weaker above the bandbending.
Change of deformation at the backbending in the yrast superdeformed band of {sup 144}Gd
Ur, C.A.; Bolzonella, G.P.; Bazzacco, D. [dell`Universita, Padova (Italy)]|[INFN, Padova (Italy)] [and others
1996-12-31
A mean lifetime measurement using the Doppler shift attenuation method has been performed at GASP in order to extract the quadrupole moment of the yrast SD band of {sup 144}Gd. The extracted intrinsic quadrupole moments, being Q{sub 0}=13.7 eb above the backbending and Q{sub 0}=11.8 eb below the backbending, are consistent with a change of deformation from {beta}{sub 2}=0.51 (at {beta}{sub 4} {approx} 0.050) to {beta}{sub 2}=0.45 (at {beta}{sub 4} {approx}0.035). The experimental results are in nice agreement with the theoretical predictions, which revealed that the second well in {sup 144}Gd arises essentially from the very favored shell structure at N=80 and Z=64. The occupation at higher frequency of the aligned N=6 proton orbitals drives the nucleus to a slightly more deformed shape.
Relation between the critical spin and angular velocity of a nucleus immediately after backbending
Nosov, V. G.; Kamchatnov, A. M.
2004-01-01
In nonspherical nuclei at $J = J_c + 0$ the relationship between the angular momentum and angular velocity immediately after backbending is the same as in the limiting case $J - J_c\\to\\infty$. This indicates that there is a unique type of cancellation of the deviations from a rigid-body moment of inertia in the upper phase $J>J_c$. An integral relationship is found which expresses this cancellation quantitatively. This formula permits $J_c$ to be calculated for the rotational bands of the eve...
Proton Orbital [541]1/2 and Backbending in 178W
WEI Zhi-Yuan; LIU Shu-Xin
2008-01-01
The microscopic mechanism of nine experimentally observed bands in 178W is investigated using the particle-number conserving method of the cranked shell model with monopole and quadrupole paring interactions.The experimental results,including the moments of inertia and angular momentum alignments of nine bands in 178W,are reproduced well by the particle-number conserving calculations,in which no free parameter is involved.Calculations demonstrate that occurrence of sharp backbending comes mainly from the contribution of high-j intruder orbitals vi13/2 or πh11/2 and their interference effect with orbitals near the Fermi surface.The w variation of the occupation probability of each cranked orbital and the contribution to moment of inertia from each cranked orbital are analyzed.
Relation between the critical spin and angular velocity of a nucleus immediately after backbending
Nosov, V.G.; Kamchatnov, A.M.
1979-05-01
In nonspherical nuclei at J=J/sub c/+0 the relationship between the angular momentum and angular velocity immediately after backbending is the same as in the limiting case J-J/sub c/..-->..infinity. This indicates that there is a unique type of cancellation of the deviations from a rigid-body moment of inertia in the upper phase J>J/sub c/. An integral relationship is found which expresses this cancellation quantitatively. This formula permits J/sub c/ to be calculated for the rotational bands of the even-even nuclei studied and the results are in agreement with those obtained by other methods of locating the Curie point. For the ground state band of W/sup 170/ the cancellation of the reciprocals of the true and rigid-body moments of inertia can be verified directly. The condition for the stability of the rotation of a nonspherical nucleus is analyzed in the Appendix in close connection with the problem of a reasonable definition of the concept of a variable moment of inertia.
Relation between the critical spin and angular velocity of a nucleus immediately after backbending
Nosov, V G
1979-01-01
In nonspherical nuclei at $J = J_c + 0$ the relationship between the angular momentum and angular velocity immediately after backbending is the same as in the limiting case $J - J_c\\to\\infty$. This indicates that there is a unique type of cancellation of the deviations from a rigid-body moment of inertia in the upper phase $J>J_c$. An integral relationship is found which expresses this cancellation quantitatively. This formula permits $J_c$ to be calculated for the rotational bands of the even-even nuclei studied and the results are in agreement with those obtained by other methods of locating the Curie point. For the ground state band of W$^{170}$ the cancellation of the reciprocals of the true and rigid-body moments of inertia can be verified directly. The condition for the stability of the rotation of a nonspherical nucleus is analyzed in the Appendix in close connection with the problem of a reasonable definition of the concept of a variable moment of inertia.
The Yrast band energy spectra of even-even nuclei 120∼130Xe and 124∼130Ba are calculated by using the O(6) limit of IBM 1 containing three-body potential. It shows that the backbending characteristics in the Yrast bands can be described fairly by O(6) + V3
Backbending and band crossing in the MR band of 137Pr
The A=130 mass region is expected to support magnetic rotation (MR) phenomenon in many nuclei. However a confirmed existence of MR is known only in few cases. To study the properties of MR in the A = 130 mass region, an experiment was performed at N.S.C. by using the first phase of the INGA clover array. The reaction used was 122Sn(19F, 4n)137Pr at 80 MeV beam energy. Here detailed results on the I=1 band are presented and confirm its magnetic rotation character
Structure of energy spectra and backbending phenomena of the isotope string of Hf with mass number between 162 and 170 have been investigated. Extend of SU(3)-limits of interacting boson model to allow a boson to break to form a quasiparticle pair, which can occupy h11/2 and i13/2 orbitals. The calculated energy levels, intensity of the electromagnetic transitions, including the ground state, β and γ band are in satisfactory agreement with observed values for the whole string of Hf isotopes. Backbending of the moment inertia of the yrast and β bands can be reproduced reasonably. Recently, very high spin states up to J=40 and a double backbending have been observed in some nuclei in rare-earth region. This phenomena might hopefully be interpreted by considering two or more bosons to break to form more quasiparticle pairs and make more bands crossing to form the double backbending
Lifetimes of high-spin states in {sup 180-184}Pt
Carpenter, M.P.; Ahmad, I.; Crowell, B. [and others
1995-08-01
Over the past few years, lifetimes were measured, using the recoil distance method, to investigate shape-coexistence and shape transitions in the even mass {sup 182-186}Pt isotopes. In all three cases, one observes a sharp increase in the transition quadrupole moment, Q{sub t}, at low frequencies followed by a rapid and significant decline in the backbending region. It was shown that the initial increase in the Q{sub t} can be explained in terms of the mixing at low spins of two bands of very different deformation, and the decline in the backbending region is brought about by mixing between the ground and a two-quasiparticle band. No lifetime information exists for these nuclei above the backbend, and there is some contention whether or not the backbend is due to the alignment of h{sub 9/2} protons, i{sub 13/2} neutrons or the near simultaneous alignment of both. Nilsson-Strutinsky calculations indicate very different shapes for the nuclei after the backbend, depending on which orbitals align. Thus, lifetime information on the states above the backbend should help determine which interpretation is correct. In order to determine the lifetimes of states in the even mass {sup 180-184}Pt nuclei above the backbend, we performed a recent experiment at Gammasphere using a {sup 64}Ni beam on Pb backed Sn targets in order to populate the nucleus of interest via a 4n reaction. At the time of the experiment, thirty-six Ge detectors were available for use in Gammasphere and approximately 100 x 10{sup 6} 3-fold and higher events were taken for each nucleus. Currently, angle-sorted matrices were created from the data, and spectra representing the ground bands show well developed lineshapes for transitions above the backbend. A full lineshape analysis of the data will begin shortly.
THE TWO-LEVEL MODEL AT FINITE-TEMPERATURE
Goodman, A.L.
1980-07-01
The finite-temperature HFB cranking equations are solved for the two-level model. The pair gap, moment of inertia and internal energy are determined as functions of spin and temperature. Thermal excitations and rotations collaborate to destroy the pair correlations. Raising the temperature eliminates the backbending effect and improves the HFB approximation.
Particle-number conserving treatment for the ground state bands in even-even transfermium nuclei
The ground state bands observed in even-even transfermium nuclei 250Fm and 252,254No are investigated by the cranked shell model with the particle-number conserving treatment for the monopole and quadrupole pairing correlations. The experimental variations of the kinematic moment of inertia with rotational frequency are reproduced very well in our calculation. Our results show backbendings of ℑ(1) at ħω ≈ 0.275 and 0.300 MeV in 252No and 254No, respectively. The detailed information about the contribution to alignment from each cranked single particle level exhibits that the backbending is mainly due to the rapidly aligned angular momentum of proton 1j15/2 [770]1/2 pairs and neutron 2h11/2 [761]3/2, 1j15/2 [734]9/2 pairs the band crossing. (author)
Energy level statistics of the U(5) and O(6) symmetries in the interacting boson model
We study the energy level statistics of the states in U(5) and O(6) dynamical symmetries of the interacting boson model and the high spin states with backbending in U(5) symmetry. In the calculations, the degeneracy resulting from the additional quantum number is eliminated manually. The calculated results indicate that the finite boson number N effect is prominent. When N has a value close to a realistic one, increasing the interaction strength of subgroup O(5) makes the statistics vary from Poisson type to Gaussian orthogonal ensemble type and further recover to Poisson type. However, in the case of N→∞, they all tend to be Poisson type. The fluctuation property of the energy levels with backbending in high spin states in U(5) symmetry involves a signal of shape-phase transition between spherical vibration and axial rotation
Isovectorial pairing plus quadrupole model in the framework of SU(3) scheme
An extended pairing plus quadrupole model, in the framework of Elliot SU scheme, is used to study the combined effects of the quadrupole-quadrupole, pairing and spin-orbit interactions on energy spectra and deformation in the yrast band of even-even nuclei in the sd and f p shells.The pairing interaction contains the three components of the iso vectorial pairing T z 0; and the results were obtained for a reasonable choice of the interaction parameter strengths. After a general review of the pairing effects on deformations, the backbending phenomenon of 48Cr was reproduced in a highly truncated Hilbert space by renormalizing the pairing strength to compensate the effective suppression of paring correlations caused by the the truncation. Likewise The backbending phenomenon in 50Cr and 52Fe is reproduced by using this method
Full text: Interacting boson model has achieved a significant success in the phenomenological description of collective motion in medium and heavy nuclei at low excitation energies [1, 2]. However, there still remain some questions: why such a simple picture with s - and d - bosons works well, even in the deformed region, without the other higher bosons. On the other hand, the cranked Hartree-Fock-Bogoliubov (HFB) approximation gives a splendid rare-earth region from the microscopic point of view. The merits of the cranked HFB approximation are its ability to treat collective - and single - particle aspects of nuclear structure on the same footing, and to take into account in a consistent way shape and pairing changes as well as rotational alignment. The main aim of this paper is to explore the microscopic foundation of the Interacting Boson Model in the framework of the cranked HFB model, and to see the mechanism of backbending in terms of the boson picture. The numerical calculations are carried out for the structure of energy spectra and backbending phenomena of the isotope string of Er, Dy. Backbending of the moment of inertia of the yrast and β states can be reproduced reasonably. The gapless super-conductor effects, in which one of the quasiparticles starts to have negative energy, begins with the 10+ states. The calculated quadrupole moment does not change much as a function of the spin of state I, although there is a delicate change corresponding to backbending phenomena. (author) Reference: 1. Arima, F.Iachello, Ann. Phys., No111, 1978, p.201.; 2. K.Baktybayev, Iader. Phys., No42, 1978, p.1031.
Microscopic insight in the study of yrast bands in selenium isotopes
Parvaiz Ahmad Dar; Sonia Verma; Rani Devi; S K Khosa
2008-05-01
The yrast bands of even-even selenium isotopes with = 68-78 are studied in the framework of projected shell model, by employing quadrupole plus monopole and quadrupole pairing force in the Hamiltonian. The oblate and prolate structures of the bands have been investigated. The yrast energies, backbending plots and reduced 2 transition probabilities and -factors are calculated and compared with the experimental data. The calculated results are in reasonably good agreement with the experiments.
{Delta}I = 2 energy staggering in normal deformed dysprosium nuclei
Riley, M.A.; Brown, T.B.; Archer, D.E. [Florida State Univ., Tallahassee, FL (United States)] [and others
1996-12-31
Very high spin states (I{ge}50{Dirac_h}) have been observed in {sup 155,156,157}Dy. The long regular band sequences, free from sharp backbending effects, observed in these dysprosium nuclei offer the possibility of investigating the occurence of any {Delta}I = 2 staggering in normal deformed nuclei. Employing the same analysis techniques as used in superdeformed nuclei, certain bands do indeed demonstrate an apparent staggering and this is discussed.
The relativistic consistent angular-momentum projected shell model study of the N=Z nucleus 52Fe
无
2009-01-01
The relativistic consistent angular-momentum projected shell model(ReCAPS) is used in the study of the structure and electromagnetic transitions of the low-lying states in the N=Z nucleus 52Fe.The model calculations show a reasonably good agreement with the data.The backbending at 12+ is reproduced and the energy level structure suggests that neutron-proton interactions play important roles.
Multiparticle excitations and identical bands in the superdeformed [sup 149]Gd nucleus
Flibotte, S.; Hackman, G.; Theisen, C.; Andrews, H.R.; Ball, G.C.; Beausang, C.W.; Beck, F.A.; Belier, G.; Bentley, M.A.; Byrski, T.; Curien, D.; de France, G.; Disdier, D.; Duchene, G.; Fallon, P.; Haas, B.; Janzen, V.P.; Jones, P.M.; Kharraja, B.; Kuehner, J.A.; Lisle, J.C.; Merdinger, J.C.; Mullins, S.M.; Paul, E.S.; Prevost, D.; Radford, D.C.; Rauch, V.; Smith, J.F.; Styczen, J.; Twin, P.J.; Vivien, J.P.; Waddington, J.C.; Ward, D.; Zuber, K. (Centre de Recherches Nucleaires, Institut National de Physique Nucleare et de Physique Particles-Centre National de la Recherche Scientifique/Universite Louis Pasteur, F-67037 Strasbourg CEDEX (France) Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4K1 (Canada) AECL Research, Chalk River Laboratories, Chalk River, Ontario K0J 1J0 (Canada) Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 3BX (United Kingdom) Science and Engineering Research Council, Daresbury Laboratory, Warrington WA4 4AD (Unit
1993-08-02
Eight superdeformed rotational bands have been observed in the [sup 149]Gd nucleus. Several excited bands have partners in neighboring nuclei which differ by up to four nucleons, with nearly identical dynamic moments of inertia and quantized [gamma]-ray phasing. These observations cannot be easily explained by theoretical models including an intrinsic scaling with mass of the moment of inertia. A paired backbend and an interaction due to an accidental degeneracy between two superdeformed levels have also been observed.
Multiparticle excitations and identical bands in the superdeformed 149Gd nucleus
Eight superdeformed rotational bands have been observed in the 149Gd nucleus. Several excited bands have partners in neighboring nuclei which differ by up to four nucleons, with nearly identical dynamic moments of inertia and quantized γ-ray phasing. These observations cannot be easily explained by theoretical models including an intrinsic scaling with mass of the moment of inertia. A paired backbend and an interaction due to an accidental degeneracy between two superdeformed levels have also been observed
Analysis of the experimental level scheme of {sup 61}Cu using computational technique
Gupta, Anuradha, E-mail: annu1gupta1@gmail.com; Verma, Preeti, E-mail: preetiverma130587@gmail.com [Research Scholar, Department of Physics and Electronics, University of Jammu, Jammu-180006 (India); Bharti, Arun, E-mail: arunbharti-2003@yahoo.co.in [Professor, Department of Physics and Electronics, University of Jammu, Jammu-180006 (India)
2015-08-28
The high-spin structure in {sup 61}Cu nucleus is studied in terms of effective two body interaction. In order to take into account the deformed BCS basis, the basis states are expanded in terms of the core eigenfunctions. Yrast band with some other bands havew been obtained and back-bending in moment of inertia has also been calculated and compared with the available experimental data for {sup 61}Cu nucleus. On comparing the available experimental as well as other theoretical data, it is found that the treatment with PSM provides a satisfactory explanation of the available data.
Investigation of band structure of {sup 103,105}Rh using microscopic computational technique
Kumar, Amit, E-mail: akbcw2@gmail.com [Research Scholar, Department of Physics and Electronics, University of Jammu, Jammu-180006 (India); Singh, Suram, E-mail: suramsingh@gmail.com [Assistant Professor, Department of Physics Govt. Degree College, Kathua-184142 (India); Bharti, Arun, E-mail: arunbharti-2003@yahoo.co.in [Professor, Department of Physics and Electronics, University of Jammu, Jammu-180006 (India)
2015-08-28
The high-spin structure in {sup 61}Cu nucleus is studied in terms of effective two body interaction. In order to take into account the deformed BCS basis, the basis states are expanded in terms of the core eigenfunctions. Yrast band with some other bands havew been obtained and back-bending in moment of inertia has also been calculated and compared with the available experimental data for {sup 61}Cu nucleus. On comparing the available experimental as well as other theoretical data, it is found that the treatment with PSM provides a satisfactory explanation of the available data.
Projected Shell Model Study of Yrast States of Neutron-Deficient Odd-Mass Pr Nuclei
Ibanes, A. [Instituto de Fisica, Mexico; Ortiz, Mark E [ORNL; Velazquez, V. [Universidad Nacional Autonoma de Mexico (UNAM); Galindo-Uribarri, Alfredo {nmn} [ORNL; Hess, P. O. [Universidad Nacional Autonoma de Mexico (UNAM); Sun, Y. [Shanghai Jiao Tong University, Shanghai
2011-01-01
A wide variety of modern instruments allow us to study neutron-deficient nuclei in the A = 130 mass region. Highly deformed nuclei have been found in this region, providing opportunities to study the deformed rotational bands. The description of the 125,127,129,131,133Pr isotopes with the projected shell model is presented in this paper. Good agreement between theory and experiment is obtained and some characteristics are discussed, including the dynamic moment of inertia J (2), kinetic moment of inertia J (1), the crossing of rotational bands, and backbending effects.
Projected shell model study of yrast states of neutron-deficient odd-mass Pr nuclei
A wide variety of modern instruments allow us to study neutron-deficient nuclei in the A=130 mass region. Highly deformed nuclei have been found in this region, providing opportunities to study the deformed rotational bands. The description of the 125,127,129,131,133Pr isotopes with the projected shell model is presented in this paper. Good agreement between theory and experiment is obtained and some characteristics are discussed, including the dynamic moment of inertia J(2), kinetic moment of inertia J(1), the crossing of rotational bands, and backbending effects.
Projected shell model study of neutron-deficient 122Ce
Rani Devi; B D Sehgal; S K Khosa
2006-09-01
The observed excited states of 122Ce nucleus have been studied in the frame-work of projected shell model (PSM). The yrast band has been studied up to spin 26 ħ. The first band crossing has been predicted above a rotational frequency of 0.4 MeV/ħ that corresponds to first backbending. The calculation reproduces the experimentally observed ground state band up to spin 14ħ. The electromagnetic quantities, transition quadrupole moments and -factors are predicted and there is a need to measure these quantities experimentally.
Constrained caloric curves and phase transition for hot nuclei
Borderie, Bernard; Rivet, M F; Raduta, Ad R; Ademard, G; Bonnet, E; Bougault, R; Chbihi, A; Frankland, J D; Galichet, E; Gruyer, D; Guinet, D; Lautesse, P; Neindre, N Le; Lopez, O; Marini, P; Parlog, M; Pawlowski, P; Rosato, E; Roy, R; Vigilante, M
2013-01-01
Simulations based on experimental data obtained from multifragmenting quasi-fused nuclei produced in central $^{129}$Xe + $^{nat}$Sn collisions have been used to deduce event by event freeze-out properties in the thermal excitation energy range 4-12 AMeV [Nucl. Phys. A809 (2008) 111]. From these properties and the temperatures deduced from proton transverse momentum fluctuations, constrained caloric curves have been built. At constant average volumes caloric curves exhibit a monotonic behaviour whereas for constrained pressures a backbending is observed. Such results support the existence of a first order phase transition for hot nuclei.
Borderie, B; Rivet, M F; Raduta, Ad R; Bonnet, E; Bougault, R; Chbihi, A; Galichet, E; Guinet, D; Lautesse, Ph; Neindre, N Le; Lopez, O; Parlog, M; Rosato, E; Roy, R; Spadaccini, G; Vient, E; Vigilante, M
2012-01-01
Simulations based on experimental data obtained from multifragmenting quasifused nuclei produced in central 129Xe + natSn collisions have been used to deduce event by event freeze-out properties on the thermal excitation energy range 4-12 AMeV. From these properties and temperatures deduced from proton transverse momentum fluctuations constrained caloric curves have been built. At constant average volumes caloric curves exhibit a monotonous behaviour whereas for constrained pressures a backbending is observed. Such results support the existence of a first order phase transition for hot nuclei.
Kurter, C.; Zasadzinski, J. F.; Ozyuzer, L.; Hinks, D. G.; Gray, K. E.
2009-03-01
In order to study Joule-heating effects on small intrinsic Josephson junction (IJJ) stacks or mesas, we compare their current-voltage curves, I(V), with those of single junctions, both using Bi2.1Sr1.4Ca1.5Cu2O8+δ (Ca-Bi2212) intercalated by HgBr2. Even for small volume stacks with reduced dissipation by intercalation, there can be self-heating despite the absence of the commonly seen backbending of I(V). This conclusion is based on distinctive features of I(V) of intermediate size mesas which were absent in single junctions.
IBM-2 calculation of band mixing in 132Ba
The band crossing in 132Ba has been investigated by using the interacting boson model. A broken neutron pair has been coupled to a collective boson core. The boson-fermion interaction hamiltonian contains terms which can transform a boson into a pair of quasiparticles and vice versa. The parameters were partly determined by fitting the collective states of 132,134Ba and the yrast states of 131Ba. The energy backbending has been satisfactorily reproduced. Good agreement of the electromagnetic moments has been reached. The structure of the wave functions has been discussed. (author)
Study of nuclear structure of odd mass 119-127I nuclei in a phenomenological approach
Singh, Dhanvir; Gupta, Anuradha; Kumar, Amit; Sharma, Chetan; Singh, Suram; Bharti, Arun; Khosa, S. K.; Bhat, G. H.; Sheikh, J. A.
2016-08-01
By using the phenomenological approach of Projected Shell Model (PSM), the positive and negative-parity band structures of odd mass neutron-rich 119-127I nuclei have been studied with the deformed single-particle states generated by the standard Nilsson potential. For these isotopes, the band structures have been analyzed in terms of quasi-particles configurations. The phenomenon of backbending in moment of inertia is also studied in the present work. Besides this, the reduced transition probabilities, i.e. B (E 2) and B (M 1), are obtained from the PSM wavefunction for the first time for yrast bands of these isotopes.
Rotational spectra and parity splitting in nuclei with strong octupole correlations
A formula is suggested to describe the energies of positive- and negative-parity states belonging to the ground-state alternating-parity rotational bands in nuclei with significant octupole correlations. The agreement with experimental data is quite good for actinide nuclei. This formula corresponds to the parity splitting from a one-dimensional potential well. It leads to a common moment of inertia for both parities at least for low angular momenta. At high angular momenta a slight difference in the moments of inertia is found, which is presumably due to backbending. ((orig.))
Investigation of band structure of 103,105Rh using microscopic computational technique
The high-spin structure in 61Cu nucleus is studied in terms of effective two body interaction. In order to take into account the deformed BCS basis, the basis states are expanded in terms of the core eigenfunctions. Yrast band with some other bands havew been obtained and back-bending in moment of inertia has also been calculated and compared with the available experimental data for 61Cu nucleus. On comparing the available experimental as well as other theoretical data, it is found that the treatment with PSM provides a satisfactory explanation of the available data
Recent developments of the projected shell model based on many-body techniques
Sun Yang
2015-01-01
Full Text Available Recent developments of the projected shell model (PSM are summarized. Firstly, by using the Pfaffian algorithm, the multi-quasiparticle configuration space is expanded to include 6-quasiparticle states. The yrast band of 166Hf at very high spins is studied as an example, where the observed third back-bending in the moment of inertia is well reproduced and explained. Secondly, an angular-momentum projected generate coordinate method is developed based on PSM. The evolution of the low-lying states, including the second 0+ state, of the soft Gd, Dy, and Er isotopes to the well-deformed ones is calculated, and compared with experimental data.
In-beam spectroscopic study of 135Pr was made using 91 MeV 120Sn(19F,4n) reaction. A strong negative parity proton band based on the h/sub 11/2-/ 1/2[550] configuration with α = -1/2 was observed. Possibly α = +1/2 unfavored band is observed. Also two positive parity proton bands are observed most likely based on the g/sub 7/2+/ 5/2[413] configurations with α = +-1/2. In all cases (except for the (π,α) = (-,+1/2) band) the backbending is caused by alignment of two h/sub 11/2-/ 9/2[514] quasi-neutrons. For the strongly decoupled π(-) bands the observed signature splitting decreases with increasing rotational frequency. The signature splitting of the positive parity bands increases with rotational frequency and then inverts above the backbending. This is interpreted to be caused by the quasi-neutrons, which drive the γ-deformation to the negative values. 18 refs., 6 figs
Shape changes and electromagnetic properties of odd-proton rare-earth nuclei
Very rapidly rotating odd-proton and odd-odd rare earth nuclei have been studied using in-beam gamma-ray spectroscopy following heavy-ion reactions. The nucleus 171Re was studied using the reaction 123Sb(52Cr,4n)171Re. A back-bend in the proton i13/2 band was fully delineated for the first time, a second back-bend was observed in the 5/2+[402] band and other bands were extended to higher spin. Band crossings were interpreted using the Cranked Shell Model and three-band mixing calculations. Deformations as functions of spin, based on diabatic configurations, have been calculated for proton i13/2 and h9/2 bands in Re and Ir isotopes. The nuclei 173,174Ta were studied using a 19F beam on a 160Gd target. A total of 16 bands have been identified and interpreted in terms of different quasiparticle excitations. Weak interband transitions between the pseudospin doublet, composed of the 5/2+[402] and 7/2+[404] band, together with accurately measured intraband mixing ratios were compared with particle-rotor calculations. A total of 10 rotational bands were identified in the odd-odd nucleus 174Ta. 38 refs, 20 figs, 3 tabs
Magnetic moments of high spin rotational states in 158Dy and 164Dy+
For the study of their magnetic moments yrast states in 158Dy and 164Dy were excited via the multiple-Coulomb excitation by a 4.7 MeV/u 208Pb beam. Hereby especially the question was of interest, how the one-particle effects in the nuclear structure in the region of the backbending anomaly in 158Dy take effects on the g-factors of the high spin states in this region. The particle-γ angular correlations perturbed in the transient magnetic field during the passing of the excited Dy ions through a thin magnetized iron foil were measured. By the selective position-sensitive detection of Dy recoil ions and Pb projectiles under forward angles it was possible to determine additionally to the g-factors in the backbending region also g-factors in the spin region I 158Dy and 164Dy by detection of the particle-γ correlations precessing in the static hyperfine field after implantation in iron. The static hyperfine field was at the 4+ state in 164Dy determined to B (Dy,Fe) = 245+-25 T. The g-factors were determined by comparison of the experimental results with calculations of the perturbed angular correlations by time-differential regarding of the population and de-excitation of the yrast states as well as by precession and hyperfine-relaxation effects during the flight of the Dy ions in the vacuum. (orig./HSI)
Effects of the quark-hadron phase transition on highly magnetized neutron stars
Franzon, B.; Gomes, R. O.; Schramm, S.
2016-08-01
The presence of quark-hadron phase transitions in neutron stars can be related to several interesting phenomena. In particular, previous calculations have shown that fast rotating neutron stars, when subjected to a quark-hadron phase transition in their interiors, could give rise to the backbending phenomenon characterized by a spin-up era. In this work, we use an equation of state composed of two phases, containing nucleons (and leptons) and quarks. The hadronic phase is described in a relativistic mean field formalism that takes many-body forces into account, and the quark phase is described by the MIT bag model with a vector interaction. Stationary and axi-symmetric stellar models are obtained in a self-consistent way by solving numerically the Einstein-Maxwell equations by means of a pseudo-spectral method. As a result, we obtain the interesting backbending phenomenon for fast spinning neutron stars. More importantly, we show that a magnetic field, which is assumed to be axi-symmetric and poloidal, can also be enhanced due to the phase transition from normal hadronic matter to quark matter on highly magnetized neutron stars. Therefore, in parallel to the spin-up era, classes of neutron stars endowed with strong magnetic fields may go through a "magnetic-up era" in their lives.
Stretching the Spines of Gymnasts: A Review.
Sands, William A; McNeal, Jeni R; Penitente, Gabriella; Murray, Steven Ross; Nassar, Lawrence; Jemni, Monèm; Mizuguchi, Satoshi; Stone, Michael H
2016-03-01
Gymnastics is noted for involving highly specialized strength, power, agility and flexibility. Flexibility is perhaps the single greatest discriminator of gymnastics from other sports. The extreme ranges of motion achieved by gymnasts require long periods of training, often occupying more than a decade. Gymnasts also start training at an early age (particularly female gymnasts), and the effect of gymnastics training on these young athletes is poorly understood. One of the concerns of many gymnastics professionals is the training of the spine in hyperextension-the ubiquitous 'arch' seen in many gymnastics positions and movements. Training in spine hyperextension usually begins in early childhood through performance of a skill known as a back-bend. Does practising a back-bend and other hyperextension exercises harm young gymnasts? Current information on spine stretching among gymnasts indicates that, within reason, spine stretching does not appear to be an unusual threat to gymnasts' health. However, the paucity of information demands that further study be undertaken. PMID:26581832
Effects of the quark-hadron phase transition on highly magnetized neutron stars
Franzon, B; Schramm, S
2016-01-01
The presence of quark-hadron phase transitions in neutron stars can be related to several interesting phenomena. In particular, previous calculations have shown that fast rotating neutron stars, when subjected to a quark-hadron phase transition in their interiors, could give rise to the backbending phenomenon characterized by a spin-up era. In this work, we use an equation of state composed of two phases, containing nucleons (and leptons) and quarks. The hadronic phase is described in a relativistic mean field formalism that takes many-body forces into account, and the quark phase is described by the MIT bag model with a vector interaction. Stationary and axi-symmetric stellar models are obtained in a self-consistent way by solving numerically the Einstein-Maxwell equations by means of a pseudo-spectral method. As a result, we obtain the interesting backbending phenomenon for fast spinning neutron stars. More importantly, we show that a magnetic field, which is assumed to be axi-symmetric and poloidal, can al...
Spectroscopy of nuclei far from stability
Sheline, R K
1976-01-01
Spherical and deformed shell energies are calculated for both the simple harmonic oscillator and the modified harmonic oscillator. When these shell effects are added to pairing and liquid drop energies, total energies are produced which suggest special stabilities for a number of nuclear regions far from the line of beta stability. The regions discussed are spherical closed shells with emphasis on /sup 132/Sn, new regions of nuclear deformation with emphasis on the neutron deficient Ra's and Th's, /sup 80/Zr, /sup 104/Zr, /sup 202/Rn, and /sup 232/Rn, and coexistence with emphasis on the neutron deficient Gd's, the neutron deficient Ir's and especially the neutron deficient Hg's. The spectroscopy of very high spin states is briefly discussed in terms of decoupled bands, backbending up to spins of approximately 24/sup +/ and of continuum gamma rays depopulating much higher spin states. Calculations relating the very high spin states to nuclear shapes are also presented. (48 refs).
Zhang, ZhenHua
2016-07-01
The high-spin rotational properties of two-quasiparticle bands in the doubly-odd 166Ta are analyzed using 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 alignments and their variations with the rotational frequency hω are reproduced very well by the particle-number conserving calculations, which provides a reliable support to the configuration assignments in previous works for these bands. The backbendings in these two-quasiparticle bands are analyzed by the calculated occupation probabilities and the contributions of each orbital to the total angular momentum alignments. The moments of inertia and alignments for the Gallagher-Moszkowski partners of these observed two-quasiparticle rotational bands are also predicted.
Cluster structure and collective behavior of the nucleus 48Cr
The structure of the nucleus 48Cr was investigated by the 40Ca+α+α orthogonality condition model (OCM). The energy spectra, electromagnetic transitions, and spectroscopic factors for the α+ 44Ti and 8Be+ 40Ca channels were calculated and are discussed herein. The observed energies and E2 transitions of the yrast band, which show collective behavior, were found to be well reproduced by the cluster model. Some exotic 2α-cluster states with ''Ca-α-α''- and ''α-Ca-α''-like configurations are predicted near the 2α threshold. The structures of the states were analyzed through the wave functions. The mechanism of backbending of the yrast band can be explained naturally in terms of the cluster-coupling scheme
Decoupling effects in the light mass barium isotopes
High spin states in 126128132Ba nuclei have been populated by (HI,xn) reactions and coincidence spectra, angular distribution and polarization of the deexcitation gammas have been used to determine the spins, parities, and decay schemes for these states. The ground-state rotational band in 126Ba is strongly excited up to I = 16+ and possibly 18+. A marked backbend occurs at the yrast 12+ state and a second nearby 12+ state appears to be a continuation of the ground-state band. An odd spin negative parity band with spins between 7- and 15- also was strongly excited. Similar behavior is observed in 128Ba while a more complicated spectrum is excited in 132Ba. Two-quasiparticle-plus-rotor band mixing calculations have been performed. The observed high spin behavior in 126128Ba is well reproduced by these calculations, demonstrating the importance of decoupling of two quasiparticles in these nuclei. (Auth.)
High spin spectroscopy of 123Ba and alignment processes for A ≅ 120
The level scheme of 123Ba has been extended. Bands based on the [523]7/2- and [402]5/2+ Nilsson configurations were established to spins 59/2 (67/2 tentatively) and 29/2, respectively. The first backbend in this region is found to be caused by the alignment of a pair of h11/2 protons. For the first time in this mass region there is evidence for a second crossing due to the alignment of an h11/2 neutron pair in a neutron h11/2 band. The experimental results are compared with self-consistent cranking calculations. A previous suggestion that large γ-deformation is needed to explain the observed bandheads is not supported. (orig.)
Cluster structure and collective behavior of the nucleus sup 4 sup 8 Cr
Sakuda, T
2002-01-01
The structure of the nucleus sup 4 sup 8 Cr was investigated by the sup 4 sup 0 Ca+alpha+alpha orthogonality condition model (OCM). The energy spectra, electromagnetic transitions, and spectroscopic factors for the alpha+ sup 4 sup 4 Ti and sup 8 Be+ sup 4 sup 0 Ca channels were calculated and are discussed herein. The observed energies and E2 transitions of the yrast band, which show collective behavior, were found to be well reproduced by the cluster model. Some exotic 2 alpha-cluster states with ''Ca-alpha-alpha''- and ''alpha-Ca-alpha''-like configurations are predicted near the 2 alpha threshold. The structures of the states were analyzed through the wave functions. The mechanism of backbending of the yrast band can be explained naturally in terms of the cluster-coupling scheme.
Investigation of the rotational nuclei 167168Hf and 170171W and the shell-model nucleus 26Mg
Two gamma-gamma coincidence experiments on neighbouring nuclei that exhibit the backbending phenomenon are described. The first experiment performed with the cyclotron of the KVI at Groningen is an investigation of 167Hf and 168Hf, whereas in the second experiment, performed at the cyclotron facility of Louvain University, high spin states are studied and compared with predictions of the cranked shell model. A new method for the correction of the large background of Compton-scattered events is described. Apart from this, an investigation of the single particle (d,p) transfer reaction at 26Mg has been performed with the van de Graaff tandem accelerator at 14 MeV. Specroscopic factors are presented for many levels up to an excitation energy of 8 MeV. Several new spin assignments could be made. (Auth.)
High spin levels in 62Zn, 64Zn, 66Zn, and 68Zn
Investigation by in-beam gamma spectroscopy of high-spin states in the even zinc isotopes has been made using the Ni(α,2nγ)Zn reactions at Esub(α) approximately equal to 30MeV for 62Zn, 64Zn and 66Zn, and the 65Cu(α,pγ) reaction at Esub(α) approximately equal to 18MeV for 68Zn. The high-spin states feeding by varying the incident particles: p,3He,α,12C is discussed. It is pointed out that the gsub(9/2) orbital plays an important role in the structure of the high-spin states. The variation of the inertia momentum throughout the yrast line shows a backbending behavior and a shape transition associated to the occurence, for J>6, of rotational states is speculated
Zhang, Zhen-Hua
2016-01-01
The high-spin rotational properties of two-quasiparticle bands in the doubly-odd ${}^{166}$Ta are analyzed using 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 alignments and their variations with the rotational frequency $\\hbar\\omega$ are reproduced very well by the particle-number conserving calculations, which provides a reliable support to the configuration assignments in previous works for these bands. The backbendings in these two-quasiparticle bands are analyzed by the calculated occupation probabilities and the contributions of each orbital to the total angular momentum alignments. The moments of inertia and alignments for the Gallagher-Moszkowski partners of these observed two-quasiparticle rotational bands are also predicted.
U(5) Symmetry of Even 96,98Ru Isotopes Under the Framework of Interacting Boson Model (IBM-1)
Sharrad, Fadhil I.; Hossain, I.; Ahmed, I. M.; Abdullah, Hewa Y.; Ahmad, S. T.; Ahmed, A. S.
2015-06-01
In this paper, the yrast bands of the even 96,98Ru isotopes are studied within the framework of the interacting boson model-1 (IBM-1), using the MATLAB computer code (IBM-1.Mat). The theoretical energy levels are obtained for the 96,98Ru isotopes, with neutron numbers 52 and 54, up to spin-parity 16+ and 12+, respectively. The ratio of the excitation energies of the first 4+ to the first 2+ excited states ( R 4/2), the backbending curves and the potential energy surfaces are also calculated. The calculated and experimental R4/2 values show that the 96,98Ru nuclei have U(5) dynamic symmetry. The calculated energies of the yrast states are compared with experimental results and they are shown to be in good agreement with the data. The contour plots of the potential energy surfaces show two interesting nuclei having a slightly oblate but almost spherical vibrator-like character.
The evolution properties of even–even 100-110Pd nuclei
The properties of the yrast states for 100-110Pd even–even (e–e) nuclei have been established. The relation between the moment of inertia 2ϑ/ℏ2 and the square of the rotational energy (ℏω)2 has been drawn to identify the back-bending that may occur at a certain state for each isotope. The relation between gamma-energy over spin Eγ/I as a function of spin I has been drawn to determine the evolution in each isotope ranging from vibration to rotational properties. The suitable limit in the interacting boson model IBM-1 has been used to calculate the yrast states for each isotope, which are then compared with the experimental results. (author)
Bejger, M; Haensel, P; Zdunik, J L; Fortin, M
2016-01-01
We explore the implications of a strong first-order phase transition region in the dense matter equation of state in the interiors of rotating neutron stars, and the resulting creation of two disjoint families of neutron-stars' configurations (the so-called high-mass twins). Rotating, axisymmetric and stationary stellar configurations are obtained numerically in the framework of general relativity, and their global parameters and stability are studied. The equation of state-induced instability divides stable neutron star configurations into two disjoint families: neutron stars (second family) and hybrid stars (third family), with an overlapping region in mass, the high-mass twin star region. These two regions are divided by an instability strip. Its existence has interesting astrophysical consequences for rotating neutron stars. We note that it provides a "natural" explanation for the rotational frequency cutoff in the observed distribution of neutron stars spins, and for the apparent lack of back-bending in ...
Zhang, Zhen-Hua
2016-01-01
The recently observed two high-spin rotational bands in the proton emitter $^{113}$Cs are investigated using the cranked shell model with pairing correlations treated by a particle-number conserving method, in which the Pauli blocking effects are taken into account exactly. By using the configuration assignments of band 1 ($\\pi 3/2^+[422], \\alpha = -1/2$) and band 2 ($\\pi 1/2^+[420], \\alpha = 1/2$), the experimental moments of inertia and quasiparticle alignments can be well reproduced by the present calculations, which in turn strongly support these configuration assignments. Furthermore, by analyzing the occupation probability $n_\\mu$ of each cranked Nilsson level near the Fermi surface and the contribution of each orbital to the angular momentum alignments, the backbending mechanism of these two bands is also investigated.
Experimental and theoretical investigation of anomalous behavior in rotational bands at high spin
High spin states of the barium nuclei have been investigated via the 114Cd(16O,4n)126Ba, 120Sn(12C,4n)128Ba and 124Sn(12C,4n)132Ba reactions. The even spin positive parity yrast band in 126Ba has been excited up to the 16+, and possibly the 18+ state. In addition, another strongly excited band was excited with spins and parities: 7-, 9-, 11-, 13- and 15-. In 128Ba, the even spin positive parity band has been excited up to the 12+ state. Backbending seems to begin at the 12+ state. Two-quasiparticles-plus-rotor bandmixing calculations have been performed in order to explain the backbending and the anomalous negative parity bands observed in 126128Ba and several other nuclei. The test case of 68156Er88 was studied in detail. Good agreement with experimental excitation energies was obtained. The E2 transition rates between the negative parity yrast states were estimated for 156Er. Strongly enhanced rates are found within the states of odd spin, and within the state of even spin. The values of the g-factors were also estimated for the two-quasineutron yrast states in 156Er, showing considerable deviations from the rotational values. The calculation was applied, with very similar results to 56126Ba70. Reasonable fits to the excitation energies were obtained. The case of 46104Pd58 was considered, and very similar results were obtained. The nucleus 80192Hg112 was also studied. No reasonable fit was obtained for the negative parity states. The above evidence suggests that decoupling effects are responsible for the anomalous high spin behavior of the nuclei considered
This paper presents new theoretical results for rotational population patterns in the nuclear SQUID effect. (The term nuclear SQUID is in analogy to the solid-state Superconducting Quantum Interference Devices.) The SQUID effect is an interesting new twist to an old quest to understand Coriolis anti-pairing (CAP) effects in nuclear rotational bands. Two-neutron transfer reaction cross sections among high-spin states have long been touted as more specific CAP probes than other nuclear properties. Heavy projectiles like Sn or Pb generally are recommended to pump the deformed nucleus to as high spin as possible for transfer. The interference and sign reversal of 2n transfer amplitudes at high spin, as predicted in the early SQUID work imposes the difficult requirement of Coulomb pumping to near back-bending spins at closest approach. For Pb on rare earths we find a dramatic departure from sudden-approximation, so that the population depression occurs as low as final spin 10h. 14 refs., 8 figs
U(5) symmetry of even {sup 96,98}Ru isotopes under the framework of interacting Boson model (IBM-1)
Sharrad, Fadhil I.; Ahmed, A.S. [Department of Physics, College of Science, Kerbala University, Karbala (Iraq); Hossain, I., E-mail: mihossain@kau.edu.sa [Department of Physics, Rabigh College of Science and Arts, King Abdulaziz University, Rabigh (Saudi Arabia); Ahmed, I.M. [Department of Physics, College of Education, Mosul University, Mosul (Iraq); Abdullah, Hewa Y. [Department of Physics, College of Science Education, Salahaddin University, Erbil, KRG (Iraq); Ahmad, S.T. [Department of Physics, Faculty of Science, Koya University, Koya, KRG (Iraq)
2015-06-15
In this paper, the yrast bands of the even {sup 96,98}Ru isotopes are studied within the framework of the interacting boson model-1 (IBM-1), using the MATLAB computer code (IBM-1.Mat). The theoretical energy levels are obtained for the {sup 96,98}Ru isotopes, with neutron numbers 52 and 54, up to spin-parity 16{sup +} and 12{sup +}, respectively. The ratio of the excitation energies of the first 4{sup +} to the first 2{sup +} excited states (R{sub 4/2}), the backbending curves and the potential energy surfaces are also calculated. The calculated and experimental R{sub 4/2} values show that the {sup 96,98}Ru nuclei have U(5) dynamic symmetry. The calculated energies of the yrast states are compared with experimental results and they are shown to be in good agreement with the data. The contour plots of the potential energy surfaces show two interesting nuclei having a slightly oblate but almost spherical vibrator-like character. (author)
Rotating neutron stars with exotic cores: masses, radii, stability
A set of theoretical mass-radius relations for rigidly rotating neutron stars with exotic cores, obtained in various theories of dense matter, is reviewed. Two basic observational constraints are used: the largest measured rotation frequency (716Hz) and the maximum measured mass (2M CircleDot). The present status of measuring the radii of neutron stars is described. The theory of rigidly rotating stars in general relativity is reviewed and limitations of the slow rotation approximation are pointed out. Mass-radius relations for rotating neutron stars with hyperon and quark cores are illustrated using several models. Problems related to the non-uniqueness of the crust-core matching are mentioned. Limits on rigid rotation resulting from the mass-shedding instability and the instability with respect to the axisymmetric perturbations are summarized. The problem of instabilities and of the back-bending phenomenon are discussed in detail. Metastability and instability of a neutron star core in the case of a first-order phase transition, both between pure phases, and into a mixed-phase state, are reviewed. The case of two disjoint families (branches) of rotating neutron stars is discussed and generic features of neutron-star families and of core-quakes triggered by the instabilities are considered. (orig.)
U(5) symmetry of even 96,98Ru isotopes under the framework of interacting Boson model (IBM-1)
In this paper, the yrast bands of the even 96,98Ru isotopes are studied within the framework of the interacting boson model-1 (IBM-1), using the MATLAB computer code (IBM-1.Mat). The theoretical energy levels are obtained for the 96,98Ru isotopes, with neutron numbers 52 and 54, up to spin-parity 16+ and 12+, respectively. The ratio of the excitation energies of the first 4+ to the first 2+ excited states (R4/2), the backbending curves and the potential energy surfaces are also calculated. The calculated and experimental R4/2 values show that the 96,98Ru nuclei have U(5) dynamic symmetry. The calculated energies of the yrast states are compared with experimental results and they are shown to be in good agreement with the data. The contour plots of the potential energy surfaces show two interesting nuclei having a slightly oblate but almost spherical vibrator-like character. (author)
In-beam studies of high-spin states of actinide nuclei
High-spin states in the actinides have been studied using Coulomb- excitation, inelastic excitation reactions, and one-neutron transfer reactions. Experimental data are presented for states in 232U, 233U, 234U, 235U, 238Pu and 239Pu from a variety of reactions. Energy levels, moments-of-inertia, aligned angular momentum, Routhians, gamma-ray intensities, and cross-sections are presented for most cases. Additional spectroscopic information (magnetic moments, M1/E2 mixing ratios, and g-factors) is presented for 233U. One- and two-neutron transfer reaction mechanisms and the possibility of band crossings (backbending) are discussed. A discussion of odd-A band fitting and Cranking calculations is presented to aid in the interpretation of rotational energy levels and alignment. In addition, several theoretical calculations of rotational populations for inelastic excitation and neutron transfer are compared to the data. Intratheory comparisons between the Sudden Approximation, Semi-Classical, and Alder-Winther-DeBoer methods are made. In connection with the theory development, the possible signature for the nuclear SQUID effect is discussed. 98 refs., 61 figs., 21 tabs
Multiparticle excitations in the 149 Gd superdeformed nucleus. Signature of new C4 nucleus symmetry
The use of 8 π and EUROGAM phase I multi-detectors for the study of high spin states of 149 Gd nucleus has revealed unexpected new phenomenons about the superdeformation in this nucleus. The new excited bands confirm the omnipresence of twin bands phenomenon. A new multi-particle excitation (two protons and one neutron) has been discovered. Thanks to the second generation EUROGAM detector, unexpected discoveries such as C4 symmetry, level interactions, complete backbending were obtained for the second potential well. The knowledge of interacting levels gives informations about the nucleon-nucleon residual interaction and could allow the determination of SD bands excitation energy. The complex processing and analysis of high multiplicity events has led to the development of new computing tools. An automatic band research program has been written for the discovery of new excited bands, and an exact method for the elimination of uncorrected events has been developed. The improvements of multi-detector performances should allow the discovery of more exceptional phenomenons and new anomalies in the SD bands. (J.S.). 222 refs., 86 figs., 38 tabs
High spin gamma-ray coincidence spectroscopy with large detector arrays
In-beam γ-ray spectroscopy has been used to study rapidly rotating nuclei in the rare-earth region. The experiments were performed using the high-resolution multi detector arrays ESSA30 and TESSA3 at the Nuclear Structure Facility, Daresbury Laboratories in Great Britain and the NORDBALL at the Niels Bohr Tandem Accelerator at Risoe in Denmark. The studied nuclei were produced using heavy-ion induced fusion-evaporation reactions. New techniques for the analysis of γ-γ correlation spectra were developed. These involves viewing the two-dimensional γ-γ spectrum as well as projection in both energy axes, determination of centroids and volumes of peaks and full two-dimensional Gauss fits of an arbitrarily shaped area. The data acquisition system of the NORDBALL multi detector array is presented. In two of the studied nuclei (167Lu and 163Tm) the strongly shape driving πh9/2[541]1/2- is studied. The shift to larger frequency of the neutron AB crossing in these decay sequences is not fully understood. The study of 171Re revealed a second backbend of the [402]5/2+ band. The observed bandcrossings are interpreted using the CSM and three-band mixing calculations. The study of 171,172W revealed five new bands and although these nuclei are expected to be stably deformed the small differences in the formation showed to be crucial in order to reproduce data well. (au)
Bandcrossing of magnetic rotation bands in 137Pr
The odd mass nucleus 137Pr has been studied to high spins in order to investigate the magnetic rotation phenomenon in mass 130 region using the 122Sn(19F,4n)137Pr reaction at a beam energy of 80 MeV. A known ΔI=1 band has been extended to Jπ=47/2- with the addition of three new transitions. Directional Correlation of Oriented Nuclei (DCO) ratios and linear polarization measurements have been performed to assign the multipolarities of gamma transitions and the spins and parities of the energy levels in this band, now established as the M1 band. The combination of M1 transitions along with cross over E2 transitions have been observed in this band for the first time. The experimentally deduced B(M1)/B(E2) ratios show a decrease with increasing spin after band-crossing suggesting magnetic rotation. TAC calculations for the 3qp: πh11/2 x ν(h11/2)-2 configuration reproduce the experimental observations in the lower spin part of the ΔI=1 band and the 5qp: πh11/2(g7/2)2 x ν(h11/2)-2 configuration reproduces the ΔI=1 band at higher spins; the crossing of the bands based on the two configuration leads to a back-bending also. Theoretical calculations also support a magnetic rotation nature for both the configurations
Bauer, H.
1998-12-31
The scattering system {sup 162}Dy {yields} {sup 116}Sn has been examined at energies in the vicinity of the Coulomb barrier using the Heidelberg-Darmstadt Crystal Ball spectrometer combined with 5 Germanium-CLUSTER detectors. In order to study pairing correlations as a function of angular momentum cold events were selected in the 2n stripping channel by identifying and suppressing the dominant hot part of the transfer with the Crystal Ball. The CLUSTER detectors with their high {gamma}-efficiency were used to identify the transfer channel and to resolve individual final states. Cross sections for the population of individual yrast states in a cold transfer reaction have been measured for the first time indicating the strong influence of higher transfer multipolarities. At small surface distances Coulomb-nuclear interferences were found to be responsible for the stronger decline of the population of higher yrast states in the transfer channel as compared to the Coulex channel. As a preparatory study for 2n transfer measurements between high spin yrast states in the backbending region of deformed nuclei the Coulomb excitation process in the crossing region of two bands in {sup 162}Dy has been analyzed. The gross properties of the measured population probabilities could be interpreted in a simple band mixing model. (orig.)
Studies of normal deformation in {sup 151}Dy
Nisius, D.; Janssens, R.V.F.; Crowell, B. [and others
1995-08-01
The wealth of data collected in the study of superdeformation in {sup 151}Dy allowed for new information to be obtained on the normally deformed structures in this nucleus. At high spin several new yrast states have been identified for the first time. They were associated with single-particle excitations. Surprisingly, a sequence was identified with energy spacings characteristic of a rotational band of normal ({beta}2 {approximately} 0.2) deformation. The bandhead spin appears to be 15/2{sup -} and the levels extend up to a spin of 87/2{sup -}. A clear backbend is present at intermediate spins. While a similar band based on a bandhead of 6{sup +} is known in {sup 152}Dy, calculations suggest that this collective prolate band should not be seen in {sup 151}Dy. In the experiment described earlier in this report that is aimed at determining the deformations associated with the SD bands in this nucleus and {sup 152}Dy, the deformation associated with this band will be determined. This will provide further insight into the origin of this band.
Self-coherent Hartree-Fock theory and the microscopic symmetries of the nucleus
A possible effects of the C4-symmetry in the superdeformed nuclei of the A ∼150 mass range has been studied microscopically using cranking Strutinsky method with the deformed Woods-Saxon potential and the Hartree-Fock approach with the Skyrme interaction. If the existence of such a symmetry is judged by the moments Q44, the results of the calculation indicate a very weak effect of this kind. Four new superdeformed bands in the 148Gd nucleus have been studied in reaction to the recent experimental observations (Eurogam Phase 2): a backbending has been tentatively observed at very high rotational frequency in the third excited band. One of the other bands exhibits a J(2) moment very similar to that of the yrast band in 152Dy, and this is the first example of identical bands which differ by four mass units. Calculations with the methods mentioned above have been used to analyse the band structure in terms of the nucleonic configurations. Calculation have been performed for some nuclear configurations predicted to involve the exotic octupole deformations (Y30-'pear shapes'; Y31-'banana mode'; Y32-'Td-symmetry' and Y33-'C3-symmetry'). While the previous calculations based on the Strutinsky method could not treat the coupling between those modes, the Hartree-Fock approach allows to see for the first time in which propositions the various modes couple. (author)
Rotating neutron stars with exotic cores: masses, radii, stability
Haensel, P; Fortin, M; Zdunik, J L
2016-01-01
A set of theoretical mass-radius relations for rigidly rotating neutron stars with exotic cores, obtained in various theories of dense matter, is reviewed. Two basic observational constraints are used: the largest measured rotation frequency is 716 Hz and the maximum measured mass is $2\\;{\\rm M}_\\odot$. Present status of measuring the radii of neutron stars is described. The theory of rigidly rotating stars in general relativity is reviewed and limitations of the slow rotation approximation are pointed out. Mass-radius relations for rotating neutron stars with hyperon and quark cores are illustrated using several models. Problems related to the non-uniqueness of the crust-core matching are mentioned. Limits on rigid rotation resulting from the mass-shedding instability and the instability with respect to the axisymmetric perturbations are summarized. The problem of instabilities and of the back-bending phenomenon are discussed in detail. Metastability and instability of a neutron star core in the case of a fi...
The Level Structure of ZIRCONIUM-83
Huttmeier, Uwe J.
The level structure of ^{83 }Zr was investigated via the fusion-evaporation reaction ^{54}Fe( ^{32}S,2pn)^{83 }Zr at beam energies between 105 and 120 MeV using in-beam gamma-ray spectroscopy techniques. gamma transitions from the decay of ^{83}Zr were unambiguously identified by means of recoil-gamma and neutron-gamma coincidence experiments. The decay scheme was constructed on the basis of Compton suppressed gamma- gamma coincidences, delayed gamma -gamma coincidences and angular distribution measurements. A total of 34 transitions were identified connecting 26 new energy levels and the previously known ground state. The lifetimes of two low-lying isomeric states were determined. A decoupled positive parity band built on the odd g_{9/2} neutron configuration was observed up to spin 37/2 hbar with the first band crossing due to proton alignment showing a sharp backbend at hbaromega ~ 0.5 MeV. A strongly coupled negative parity band based on a 5/2^- bandhead was observed up to spin 35/2 hbar . The angular momentum alignment is discussed and compared to neighboring nuclei. A theoretical analysis was performed using the Woods-Saxon cranking model. The results of the calculation are consistent with the experimental findings for ^{83}Zr and its neighbors. Triaxial shapes are predicted for all observed bands in ^{83}Zr. At higher angular momenta a transition to well deformed prolate bands including the h_{11/2} intruder orbitals is expected.
Rotating neutron stars with exotic cores: masses, radii, stability
Haensel, P.; Bejger, M.; Fortin, M.; Zdunik, L. [Polish Academy of Sciences, N. Copernicus Astronomical Center, Warszawa (Poland)
2016-03-15
A set of theoretical mass-radius relations for rigidly rotating neutron stars with exotic cores, obtained in various theories of dense matter, is reviewed. Two basic observational constraints are used: the largest measured rotation frequency (716Hz) and the maximum measured mass (2M {sub CircleDot}). The present status of measuring the radii of neutron stars is described. The theory of rigidly rotating stars in general relativity is reviewed and limitations of the slow rotation approximation are pointed out. Mass-radius relations for rotating neutron stars with hyperon and quark cores are illustrated using several models. Problems related to the non-uniqueness of the crust-core matching are mentioned. Limits on rigid rotation resulting from the mass-shedding instability and the instability with respect to the axisymmetric perturbations are summarized. The problem of instabilities and of the back-bending phenomenon are discussed in detail. Metastability and instability of a neutron star core in the case of a first-order phase transition, both between pure phases, and into a mixed-phase state, are reviewed. The case of two disjoint families (branches) of rotating neutron stars is discussed and generic features of neutron-star families and of core-quakes triggered by the instabilities are considered. (orig.)
The high spin (J70Ga all the members (except the 3- one) of the (πpsub(3/2), νgsub(9/2)) configuration have been identified, in addition with the (πfsub(5/2), νgsub(9/2))sub(7-) and (πgsub(9/2), νgsub(9/2))sub(9+) states. In 66Ga and 68Ga most of the levels with J>7 ca be described as a result of maximum coupling of a gsub(9/2) neutron with the odd Ga core. Thus the (πgsub(9/2), νgsub(9/2))sub(9+) states have been safely located. In the same way the even Ge, the backbending effect at the Jsup(π)=8+ state is less and less pronouced from the 68Ge to the 72Ge; that can be explained by the (νgsub(9/2))2sub(8+) configuration of this state, so that the 8+→6+ γ-transition is more and more allowed with increasing N, i.e. as the νgsub(9/2) shell acts more and more in the lower yrast levels Jsup(π)=0+, 2+, 4+, 6+ configurations
In-beam studies of high-spin states of actinide nuclei
Stoyer, M.A. (Lawrence Berkeley Lab., CA (USA). Nuclear Science Div. California Univ., Berkeley, CA (USA). Dept. of Chemistry)
1990-11-15
High-spin states in the actinides have been studied using Coulomb- excitation, inelastic excitation reactions, and one-neutron transfer reactions. Experimental data are presented for states in {sup 232}U, {sup 233}U, {sup 234}U, {sup 235}U, {sup 238}Pu and {sup 239}Pu from a variety of reactions. Energy levels, moments-of-inertia, aligned angular momentum, Routhians, gamma-ray intensities, and cross-sections are presented for most cases. Additional spectroscopic information (magnetic moments, M{sub 1}/E{sub 2} mixing ratios, and g-factors) is presented for {sup 233}U. One- and two-neutron transfer reaction mechanisms and the possibility of band crossings (backbending) are discussed. A discussion of odd-A band fitting and Cranking calculations is presented to aid in the interpretation of rotational energy levels and alignment. In addition, several theoretical calculations of rotational populations for inelastic excitation and neutron transfer are compared to the data. Intratheory comparisons between the Sudden Approximation, Semi-Classical, and Alder-Winther-DeBoer methods are made. In connection with the theory development, the possible signature for the nuclear SQUID effect is discussed. 98 refs., 61 figs., 21 tabs.
Medium-spin states in 70Ge and the role of the g9/2 orbital
Medium-spin states of 70Ge have been studied via the 60Ni(12C,2pγ)70Ge reaction at 45 MeV. The ground-state band and the second 0+ band have been extended to the 12+ and 8+ states, respectively. Two negative-parity bands, one of which has a coupled structure and the other has a decoupled structure, have been observed additionally. Although the latter decoupled structure was known up to the (21-) state from a previous experiment, the part of the level scheme up to the 15- state has been largely modified by the present experiment. Backbendings observed in the positive- and negative-parity yrast bands have been compared with those of the neighboring even Ge isotopes. The experimental level structure has been compared with the shell-model calculations in the model space (2p3/2, 1f5/2, 2p1/2, 1g9/2) employing two kinds of effective interactions, one of which is an extended P+QQ interaction with monopole interactions and the other is developed from a renormalized G matrix. Microscopic structures of the observed bands have been discussed with the help of the shell-model calculations.
Characteristics of collectivity along the yrast line in even-even tungsten isotopes
Yang, Qiong; Wang, Hua-Lei; Liu, Min-Liang; Xu, Fu-Rong
2016-08-01
The collective nature of high-spin yrast states in even-even W-190160 isotopes was systematically investigated by means of pairing self-consistent Woods-Saxon-Strutinsky calculations using the total Routhian surface approach in (β2,γ ,β4) deformation space. The calculated ground-state deformations are consistent with previous calculations and available experimental data. The deformation energy curves are presented to show the shape and softness evolutions, in particular in the triaxial direction. The backbending or upbending behavior in moment of inertia is attributed to band crossing. It is found that the neutron rotation alignment is preferred for most of the W isotopes (e.g., in W-180164), while in other nuclei the competition between the neutron and proton alignments may occur, even the proton alignment is favored in the very neutron-deficient nucleus 160W. In addition, the evolution and transition between vibrational and rotational collective modes along the yrast line are investigated on the basis of the new centipedelike E-GOS (E-Gamma Over Spin) curves introduced by us, which to some extent explains the existing differences (e.g., in the moment of inertia) between theory and experiment.
The vibration states of the Skyrme model
In the paper an algebraic method for the construction of the collective Hamiltonian of the Skyrme model is treated. The Skyrme model has some phenomenological success in describing the static properties of nucleon and their interactions. The vibration spectra in the framework of the subgroup SU(5) have been discussed. Exploiting the related symmetry group it is possible to obtain the simple analytic expressions for the eigenvalues of boson Hamiltonian and for intraband transition matrix elements as well as for side feeding from one band to the other. Back-bending occurs naturally as the crossing of two bands and it can be predicted from the relative spacing of the low excited states. The algebraic properties of collective variables lead to a new quantum number N which implies in the boson representation the maximum number of phonons contained in vibrational states. Because the boson-boson interaction in SU(5) invariant Hamiltonian splits the degeneracy of the multiplets, this limits describes an anharmonic vibrator. It should be noted, we describe finite dimensional system in contrast with the geometrical description in which N→∞. It is worth noting that the knowledge of the invariance properties of Hamiltonian provides directly a solution to the eigenvalue problem. The transformation into intrinsic frame of reference has been performed explicitly. Thus, the formulae for the potential energy, the quadrupole moments are obtained as well as the spectroscopic factors for 0+ state excitation in the two nucleon transfer reactions. The proposed collective Hamiltonian is applied to the transformational nuclei Sm, Gd and Dy. The agreement between the experimental data and the theoretical description is good
Measurement of lifetimes of high spin states in the N = 106 nuclei {sup 183}Ir and {sup 182}Os
Ahmad, I.; Blumenthal, D.; Carpenter, M.P. [and others
1995-08-01
Lifetimes of high spin states in the isotones {sup 183}Ir and {sup 182}Os were measured using the Notre Dame plunger device in conjunction with the Argonne Notre Dame {gamma}-ray facility. The aim of these measurements was to determine the deformation-driving properties of the h{sub 9/2} proton intruder orbital by comparing the values of the intrinsic quadrupole moments in the ground state bands in the odd-mass Ir nucleus and the even-even Os core. Levels in these nuclei were populated by the {sup 150}Nd ({sup 37}Cl,4n) and {sup 150}Nd ({sup 36}S,4n) reactions using a {sup 37}Cl beam of 169 MeV and 164-Mev {sup 36}S beam. The {sup 150}Nd target was 0.9-g/cm{sup 2} thick and was prepared by evaporating enriched {sup 150}Nd onto a stretched 1.5-mg/cm{sup 2} gold foil. The target was covered with a layer of a 60-{mu}g/cm{sup 2} Au to prevent its oxidation. Gamma-ray spectra were accumulated for approximately 4 hours for each target-stopper distance. Data were collected for 20 target-stopper distances ranging from 16 {mu}m to 10.4 mm. Preliminary analysis indicates that it will be possible to extract the lifetimes of the levels in the yrast bands up to and including part of the backbending region with sufficient accuracy. Detailed analysis of the data is in progress.
Hüttmeier, U. J.; Gross, C. J.; Headly, D. M.; Moore, E. F.; Tabor, S. L.; Cormier, T. M.; Stwertka, P. M.; Nazarewicz, W.
1988-01-01
The level structure of 83Zr was investigated via the fusion-evaporation reaction 54Fe(32S,2pn)83Zr at beam energies between 105 and 120 MeV using in-beam γ-ray spectroscopy techniques. γ transitions from the decay of 83Zr were unambiguously identified by means of recoil-γ, neutron-γ, and x-ray-γ coincidences. The decay scheme was constructed on the basis of Compton suppressed γ-γ coincidences, delayed γ-γ coincidences, and angular distribution measurements. A total of 34 transitions were identified connecting 26 new energy levels and the previously known ground state. The lifetimes of two low-lying isomeric states were determined. A decoupled positive parity band built on the odd g9/2 neutron configuration was observed up to spin (37/2ħ with the first band crossing due to proton alignment showing a sharp backbend at ħω=0.5 Mev. A strongly coupled negative parity band based on a (5/2- bandhead was observed up to spin (35/2ħ. The angular momentum alignment is discussed and compared to neighboring nuclei. A theoretical analysis was performed using the Woods-Saxon cranking model. The results of the calculation are consistent with the experimental findings for 83Zr and its neighbors. Triaxial shapes are predicted for all observed bands in 83Zr. At higher angular momenta a transition to well-deformed prolate bands involving the h11/2 intruder orbitals is expected.
Level structures of 110,111,112,113Rh from measurements on 252Cf
Level schemes of 111Rh and 113Rh are proposed from the analysis of γ-γ-γ coincidence data from a 252Cf spontaneous fission source with Gammasphere. These schemes have the highest excitation energies and spins yet established in these nuclei, as well as weakly populated bands not reported in earlier fission- γ work. From these data, information on shapes is inferred. By analogy with lighter Z=45 odd-even isotopes, tentative spins and parities are assigned to members of several rotational bands. In this region triaxial nuclear shapes are known to occur, and we carried out calculations for 111Rh and 113Rh with the triaxial-rotor-plus-particle model. The 7/2+πg9/2 bands of both nuclei, as well as lighter isotopes studied by others, show similar signature splitting. Our model calculations give a reasonable fit to the signature splitting, collective sidebands, and transition probabilities at near-maximum triaxiality with γ≅28 deg. For the K=1/2+[431] band, experiment and model calculations do not fit well, which is accounted for by greater prolate deformation of the K=1/2+ band, a case of shape coexistence. Our data on 110,112Rh show no backbending and thus support the idea of the band crossing in the ground band of the odd-A neighbors being due to alignment of an h11/2 neutron pair. In 111,113Rh above the band crossing (spins ≅21/2(ℎ/2π)) the ground band appears to split, with two similar branches. We consider the possibility that chiral doubling may be involved, but there are not enough levels to determine that
Cyclortron-based nuclear science. Progress in research, April 1, 1982-March 31, 1983
This report contains descriptions of the activities of the research programs at the Institute and the progress on construction of the new cyclotron facility over the past year. A wide variety of both experimental and theoretical programs were underway and brief descriptions of recent progress in some areas of current interest are given. The first measurement of parity violation in the H(p,p) reaction has been completed at Ep = 47 MeV. Measurements of the vector and tensor analyzing powers A/sub y/(180), A/sub yy/180), and Z/sub zz/(00) for the 2H(d,n) 3He, 2H(d,n)X and 1H(d,n)2p reactions at E/sub d/ = 46 MeV have been performed. The giant monopole resonance has been identified in 28Si at E/sub x/ = 55/A sup 1/3/ MeV by small angle inelastic alpha scattering measurements. Further evidence for the proton character of levels causing second backbending in the Yb region has been obtained through the use of in-beam spectroscopy combined with a total multiplicity filter. Measurements of the energy spectra of H and He isotopes from the fragmentation of 320 MeV 10B projectiles in the system 10B + 181Ta lead to low momentum widths sigma/0 = 54 MeV/c) suggesting a rapid transition in momentum width between 32 and 43 MeV/nucleon. Evidence for enhanced fragment spins and shell effects in heavy-ion induced fission have been obtained. High resolution fluorine x-ray spectra of ionic solids excited by 80 MeV Ar ions have provided evidence of rapid electron transfer from the outer levels of surrounding atoms to energy matched high n states of highly ionized fluorine target atoms. In theoretical efforts, the transition from fusion and deep inelastic reactions at low energies to spectator/participant and fireball pictures at high energies has been clarified in relation to nuclear matter properties, with predictions of a multifragmentation region in between
Orogenic plateau magmatism of the Arabia-Eurasia collision zone
Allen, M. B.; Neill, I.; Kheirkhah, M.; van Hunen, J.; Davidson, J. P.; Meliksetian, Kh.; Emami, M. H.
2012-04-01
generally applicable as melt triggers. Enigmatic lavas are erupted over the thick lithosphere of Kurdistan Province, Iran. These alkali basalts and basanites have the chemical characteristics of small degree (<1%) melts in the garnet stability field. Most possess supra-subduction zone chemistry (La/Nb = 1-3), but this signature is highly variable. Similar La/Nb variability occurs in the basic lavas of Damavand volcano in the Alborz Mountains of northern Iran. Modelling suggests the depletion of residual amphibole during the progression of partial melting can explain the observed La/Nb range. This melting may occur as the result of lithospheric thickening. At depths of ~90 km, amphibole-bearing peridotite crosses an experimentally-determined "backbend" in its solidus. Melting can continue while the source remains hydrated. Such "compression" melting may apply to parts of other orogenic plateaux, including Tibet.
Delion, D. S.; Zamfir, N. V.; Raduta, A. R.; Gulminelli, F.
2013-02-01
renowned professors and researchers in nuclear physics. This proceedings volume is organized into four chapters, which reflects the traditional chapter structure of nuclear physics textbooks, but seen from the perspective of open quantum systems: INuclear structure IIDecay processes IIINuclear reactions and astrophysics IVContributions The lectures and contributions are listed alphabetically by author within each chapter. The volume contains many comprehensive reviews related to the topics of the School. The first week of the School was focused on nuclear structure and decay phenomena, considering the nucleus as an open system. Experts in these fields lectured on cluster radioactivity, the stability of superheavy nuclei, alpha-decay fine structure, fission versus fusion, beta and double beta decay and pairing versus alpha-clustering. New experimental results related to the nuclear stability of low-lying and high spin states were also presented. Recent developments at JINR—Dubna and GSI—Darmstadt international laboratories were also reported by their current or former directors. The second week of the event was dedicated to the physics of exotic nuclei, heavy ion reactions and multi-fragmentation, symmetries and phase transitions of open quantum systems. The stability of the atomic nucleus is an important and always interesting discussion point, especially in the context of newly discovered nuclear systems close to the stability line, such as proton/neutron rich or superheavy nuclei. Several lectures and contributions were focused on nuclear structure models describing low-lying states. This includes the status of density functional theory, new developments in Bohr-Mottelsohn Hamiltonian and shell-model theory, proton-neutron correlations, shape coexistence, back-bending phenomena and the thermodynamics of open quantum systems. Open systems in astrophysics, such as supernovae and neutron stars, were presented in detail by several lecturers. Important topics connected to