H. C. Chiang

NEGATIVE-PARITY STATES OF N = 88 ISOTONES IN THE INTERACTING BOSON APPROXIMATION

Abstract The negative-parity states of N =88 isotones are studied systematically in terms of the interacting boson approximation A mass-independent effective interacting boson hamiltonian reproduced energy levels very well. Unified E1 and E3 transition operators are found. The effect of p bosons on the energy spectra and electromagnetic transitions is discussed.

Effective-interaction calculation of the energy spectra of copper isotopes

SummaryEleven energy spectra of copper isotopes from58Cu to68Cu are studied in the conventional shell model. The model space is restricted to the low-seniority configurations. SomeT=0 two-body interactions are determined by a least-squares fit between the calculated and experimental low-lying energy levels. Good agreement is obtained with the observed level structure. Single-nucleon spectroscopic factors of64,66Cu are calculated and compared with experiments. The results show that the low-seniority restriction is an effective way to reduce the dimensionality of the model space for medium nuclei.RiassuntoSi studiano undici spettri di energia di isotopi di rame da58Cu a68Cu nel modello a strati convenzionale. Si restringe lo spazio modello alle configurazioni di seniorità inferiore. Alcune interazioni a due corpi conT=0 sono state determinate con un’approssimazione ai minimi quadrati fra i livelli d’energia inferiori calcolati e sperimentali. Si ottiene un buon accordo con la struttura dei livelli osservata. Si calcolano e si confrontano coi dati sperimentali i fattori spettroscopici di nucleone singolo di64,66Cu. I risultati mostrano che la limitazione alla seniorità inferiore è un metodo efficace per ridurre la dimensionalità dello spazio modello per nuclei medi.РеэюмеВ рамках стандартной оболочечной модели исследуются одиннадцать знергетических спектров иэотопов меди от58Cu до68Cu. Модельное пространство сводится к конфигурациям с малым синьоритетом. Испольэуя подгонку наименьщих квадратов между вычисленными и зкспериментальными ниэколежашими уровнями знергии, определяются некоторыеT=0 двухчастичные вэаимодействия. Получается хорощее согласие с обнаруженной структурой уровней. Вычисляются однонуклонные спектроскопические факторы иэотопов64,66Cu и сравниваются с реэультатами зкспе-риментов. Полученные реэультаты покаэывают, что ограничение, свяэанное с малым синьоритетом, представляет зффективный путь для уменьщения числа иэмерений модельного пространства для ядер вешества.

IBA calculations on the even-even Pt isotopes

Abstract By performing least-squares-fit calculations on the energy spectra of the even-even 186–196 Pt isotopes, the IBA model I and the IBA model II are compared on an equal footing. It is found that both model I and model II can fit energy spectra and absolute B (E2) transition rates reasonably well. Model II shows a distinct improvement in the energy spectra of β-bands of heavier nuclei in the isotope series. It is suggested that for regions far from the closed shells model I may be used to simulate model II as a useful phenomenological probing tool.

Weak-coupling calculation on N = 83 isotones

SummaryA proton-neutron weak-coupling model calculation is performed on those N=83 isotones that are far fromZ = 50 proton closed shell. The agreement between the experimental and the calculated energy level schemes is quite good. The result suggests that the weak-coupling model proposed by McGrory is applicable not only to even-even nuclei, but also to even-odd and odd-odd nuclei.

Shell-model studies of negative-parity states in nuclei with A=18, 19 and 20

A shell-model calculation of the negative-parity states in the A=18, 19 and 20 nuclei is presented. Assuming the nucleus 16O to be the core, an active hole is restricted to the 1p1/2 or 1p3/2 orbits, and active particles are allowed to occupy the 1d5/2 and 2s1/2 orbits. The two-body effective interaction is assumed to be a central potential which has Yukawa radial dependence. The energy spectra are calculated from a least-squares fit to the experimental data, varying the strengths of the exchange interaction and the single-particle level splittings. Spectroscopic factors and E2, E3 and M1 transition rates are calculated and compared with the observed values.

Effects of 1p3/2 and 0f5/2 hole excitations on N=50 isotones

The effects of the 1p3/2 and 0f5/2 one-hole excitations are examined for N=50 isotones. The pseudo-nucleus 100Sn is assumed to be the inert core and a two-range central-plus-tensor potential is used for the effective interaction. It is found that the calculated low-lying energy spectra agree with the experimental data quite well. Many more states can be accommodated by expansion of the model space. The transition probabilities are calculated. It is found that inclusion of 1p3/2 and 0f5/2 hole excitations in general improves the agreement between the calculated transition probabilities and experimental data.

Study of Pt isotopes in the core excited interacting boson model 1

Abstract The core exited IBM model was applied to the Pt isotopes. It was found that the energy spectra of the high-spin states as well as those of the low-spin states can be reproduced quite well. Also, it was found that there is a structure transition between 186 Pt and 188 Pt. The B (E2) values of 184 Pt were calculated and compared with recent experimental data. It was found that the general features of the B (E2) values can be reproduced qualitatively. The need of more boson core excitations is also discussed.

Effective boson calculations on Sm isotopes

Effective boson numbers are introduced in IBA-1 calculations to simulate the partial subshell closure effects at Z=64. The energy levels, wavefunctions and B(E2) values of Sm isotopes are calculated and compared with the experimental data. It is found that the agreement with the experimental data can be improved by introducing effective boson numbers in the calculations.

Phenomenological weak-coupling analysis on N = 81 isotones☆

Abstract A phenomenological np weak-coupling model is applied to N = 81 isotones. The energy spectra, stripping spectroscopic factors and electromagnetic transition probabilities are calculated and compared with experimental data. It is shown that the energy spectra and the spectroscopic factors can be reproduced quite well. The structures of the wave functions are analyzed. The discrepancies between the calculated and experimental transition probabilities suggest that the configuration mixings of the calculated wave functions are too small. The results of the calculation indicate that this model is a very efficient truncation scheme and suggest that its domain of applicability may be extended.

Study of Hf isotopes in the boson-plus-fermion-pair model

SummaryThe even-mass Hf isotopes are studied in the boson-plus-fermion-pair model. Energy spectra, effective moments of inertia andB(E2) values are calculated. It was found that the high-spin anomalies can be correlated qualitatively by the model. Possible extensions of the model are discussed.