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Sample records for fononnykh vozbuzhdenij nesfericheskikh

  1. Thermostimulated luminescence in KBr-In crystals after optical creation of electronic excitation. Termostimulirovannaya lyuminestsentsiya v kristallakh KBr-In pri opticheskom sozdanii ehlektronnykh vozbuzhdenij

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    Popov, A I [AN Latvijskoj SSR, Riga (USSR). Inst. Fiziki

    1990-01-01

    Thermal stability of the radiation defects produced in KBr-In by optical creation of the electronic excitation (optical creation of the excitons or optical ionization of In{sup +}-ions under C-band illumination) is investigated by the method of thermostimulated luminescence (TSL). A method of detection of prehistory defects, when the optical ionization of In{sup +}-ions and TSL are performed, is proposed. Quadratic dependence of V{sub 2}-center creation upon dose is shown. This dependence confirms assocative mechanism of the creation of V{sub 2}-centers from two interstitial centers.

  2. Theoretical Aspects of Phonon Dispersion Curves for Metals; Aspects Theoriques des Courbes de Dispersion des Phonons pour les Metaux; Teoreticheskie aspekty fononnykh dispersionnykh krivykh dlya metallov; Aspectos Teoricos de las Curvas de Dispersion Fononica en Metales

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    Cochran, W. [Department of Natural Philosophy, University of Edinburgh, Scotland (United Kingdom)

    1965-04-15

    Reasonably complete knowledge of the phonon dispersion curves for at least a dozen metallic elements and intermetallic compounds has now been obtained from neutron inelastic scattering experiments. The results have one feature in common: when analysed in terms of interatomic force constants they reveal the presence of comparatively long-range forces extending over several atomic spacings. The results for lead are particularly interesting; it did not prove possible to fit them by a force-constant model, but the dispersion curves for wave vectors in symmetry directions when analysed in terms of force constants between planes of atoms showed an oscillatory interatomic potential extending over distances of more than 20A. This review is concerned with recent theoretical work which has a bearing on the calculation of phonon dispersion curves for metals and the explanation of the long range of the interatomic potential. The best hope at present for a general treatment of atomic interaction in metals appears to lie in the ''method of neutral pseudo-atoms'', (a description recently coined by Ziman). This approximate theory is outlined and its relevance to Kohn anomalies in phonon dispersion curves is discussed. Experimental data for sodium is consistent with the theory, and the interatomic potential in sodium varies periodically in a distance {pi}/k{sub F}, where fik{sub F} is the Fermi momentum, as has already been demonstrated by Koenig in a different way. More exact calculations have been made for sodium by Toya and by Sham. The relationship between the different methods and other work of a more general character such as that of Harrison are discussed. (author) [French] A la suite d'experiences de dispersion inelastique des neutrons, on a maintenant une connaissance assez complete des courbes de dispersion des phonons pour une douzaine de metaux et de composes intermetalliques au moins. Les resultats presentent le caractere commun suivant: si on les analyse en fonction des constantes de forces interatomiques, ils revelent la presence de forces de portee relativement longue (plusieurs espaces atomiques). Les resultats relatifs au plomb sont particulierement interessants; il n'a pas ete possible de les ajuster au moyen d'un modele de constantes de forces, mais les courbes de dispersion pour les vecteurs d*ondes dans des directions de symetrie, analysees en fonction des constantes de forces entre plans d'atomes, accusent un potentiel interatomique oscillatoire qui s'etend sur des distances de plus de 20 A. L'auteur fait le point des travaux theoriques recents qui ont des incidences sur le calcul des courbes de dispersion des phonons pour des metaux, et tente d'expliquer la longue portee du potentiel interatomique. Il semble qu'actuellement ce soit la 'methode des pseudo-atomes neutres' (expression forgee recemment par Ziman) qui offre les meilleures chances de permettre un traitement general de l'interaction atomique dans des metaux. L'auteur donne un apercu de cette theorie et discute son importance du point de vue des anomalies de Kohn dans les courbes de dispersion des phonons. Les donnees experimentales pour le sodium sont en accord avec cette theorie et le potentiel interatomique dans le sodium varie periodiquement sur une distance {pi}/k{sub F}, hk{sub F} etant le moment de Fermi, ainsi que Koenig l'avait deja demontre d'une autre facon. Des calculs plus exacts ont ete effectues pour le sodium par Toya et par Sham. Le memoire examine les relations entre les differentes methodes, ainsi que d'autres travaux d'un caractere plus general, tels que ceux d'Harrison. (author) [Spanish] Los experimentos de dispersion inelastica de neutrones han permitido acopiar datos bastadte completos sobre las curvas de dispersion fononica correspondientes a una docena, por lo menos, de elementos metalicos y de compuestos intermetalicos. Los resultados presentan una caracteristica comun: analizados en funcion de las constantes de fuerzas interatomicas, manifiestan la presencia de fuerzas de alcance relativamente grande, que se extienden a varios espacios interatomicos. Los resultados relativos al plomo son particularmente interesantes; no fue posible ajustarlos a un modelo de constantes de fuerza, pero las curvas de dispersion de los vectores de onda en las direcciones de simetria, analizadas en funcion de las constantes de fuerza entre planos atomicos, revelan la existencia de un potencial interatomico de caracter oscilatorio que se extiende a distancias superiores a 20A. La memoria trata de trabajos teoricos recientes, relacionados con el calculo de las curvas de dispersion fononica en metales y con la explicacion del largo alcance del potencial interatomico. En la actualidad, el metodo mas prometedor para abordar con criterio general la interaccion atomica en los metales parece ser el de los 'pseudoatomos neutros ', denominacion recientemente acunada por Ziman. Se exponen los principios de esta teoria de Aproximacion y se examina su relacion con las anomalias de Kohn en las curvas de dispersion fononica. En el caso del sodio, los valores experimentales concuerdan con los datos teoricos, y el potencial interatomico varia periodicamente en la distancia {pi}/k{sub F}, donde hk{sub F} es el momento de Fermi, como ha demostrado Koenig por un procedimiento diferente. Toya y Sham han realizado calculos mas exactos para el sodio; se examinan las relaciones existentes entre los diferentes metodos y otros trabajos de indole mas general, tales como los de Harrison. (author) [Russian] V nastojashhee vremja v rezul'tate jeksperimentov po neuprugomu rassejaniju nejtronov dovol'no polno izucheny fononnye dispersionnye krivye po krajnej mere dlja djuzhiny metallicheskih jelementov i intermetallicheskih soedinenij. Rezul'taty imejut odnu obshhuju oso- oennost': analiz ih s tochki zrenija konstant mezhatomnyh sil pokazyvaet nalichie dovol'no dal'nodejstvujushhih sil, prostirajushhihsja na neskol'ko mezhatomnyh rasstojanij. Osobyj interes predstavljajut rezul'taty po svincu: okazalos' nevozmozhnym podognat' ih na osnove modeli konstanty sily, odnako dispersionnye krivye dlja volnovyh vektorov v simmetrichnyh napravlenijah, esli analizirovat' ih s tochki zrenija konstant sily mezhdu ploskostjami atomov, pokazyvajut nalichie kolebatel'nogo mezhatomnogo potenciala, prostirajushhegosja na rasstojanija, prevyshavshie 20A. Nastojashhij obzor posvjashhen poslednim teoreticheskim rabotam, imejushhim otnoshenie k raschetu fononnyh dispersionnyh krivyh dlja metallov i ob'jasneniju dal'nego dejstvija mezhatomnogo potenciala. V nastojashhee vremja naibolee obnadezhivajushhim metodom obshhej traktovki vzaimodejstvija atomov v metallah predstavljaetsja ''metod nejtral'nyh psevdoatomov'', kotoryj byl nedavno opisan Zimanom. Kratko izlozhena jeta priblizhennaja teorija i rassmotren vopros o ee spravedlivosti dlja anomalij Kona v fononnyh dispersionnyh krivyh. Jeksperimental'nye dannye po natriju soglasujutsja s teoriej, i mezhatomnyj potencial v natrii periodicheski menjaetsja na rasstojanii {pi}/k{sub F}(gde hk{sub F} - moment Fermi), kak bylo uzhe dokazano inym putem Kenigom. Bolee tochnye raschety po natriju proizveli Tojja i Sham. Rassmatrivaetsja svjaz' mezhdu razlichnymi metodami i drugimi rabotami bolee obshhego haraktera, naprimer, rabotoj Harrisona. (author)

  3. Quasiparticles and Nuclear Vibrational States; Kvazichastitsy i vibratsionnye sostoyaniya yader

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    Sorensen, R. A. [Carnegie-Mellon University, Pittsburgh, PA (United States)

    1968-12-15

    The level structure associated with various nuclear vibrations is described. It is shown how these vibrations are described in terms of particle or quasi - particle excitations by means of the harmonic random phase approximation. Vibrations corresponding to different modes of excitation are compared. Motions corresponding to the enhancement of three different simple operators are considered: (a) the E2 one-body operator, (b) the operator causing the removal or addition of a like, zero-coupled pair of nucleons from the nucleus, and (c) the operator for allowed beta decay which changes one proton to a neutron or one neutron to a proton. (author) [Russian] Da etsja opisanie str u ktu ry urovnej, svjazannyh s razlichnymi jadernymi kolebanijami. Pokazano, kak takie vibracii mogut byt' opisany s pomoshh'ju chastichnyh i kvazichastichnyh vozbuzhdenij v garmonicheskom priblizhenii metoda sluchajnyhfaz. Sravnivajutsja kolebanija, sootvetstvujushhie razlichnym tipam vozbuzhdenij. R assm atrivaju tsja dvizhenija, sootvetstvujushhie uvelicheniju trehraz lichnyh prostyh operatorov: a) odnochastichnyj operator E2-perehoda, v) operator pogloshhenija ili porozhdenija sparennyh nuklonov s nulevym momentom, s) operator razreshennogo /3-raspada, zamenjajushhij proton na nejtron ili nejtron na proton. (author)