Infinitesimal cranking for triaxial angular-momentum-projected configuration-mixing calculation and its application to the gamma vibrational band

摘要

Inclusion of time-odd components into the wave function is important forreliable description of rotational motion by the angular-momentum-projectionmethod; the cranking procedure with infinitesimal rotational frequency is anefficient way to realize it. In the present work we investigate the effect ofthis infinitesimal cranking for triaxially deformed nucleus, where there arethree independent cranking axes. It is found that the effects of cranking aboutthree axes on the triaxial energy spectrum are quite different and inclusion ofall of them considerably modify the resultant spectrum from the one obtainedwithout cranking. Employing the Gogny D1S force as an effective interaction, weapply the method to the calculation of the multiple gamma vibrational bands in$^{164}$Er as a typical example, where the angular-momentum-projectedconfiguration-mixing with respect to the triaxial shape degree of freedom isperformed. With this method, both the $K=0$ and $K=4$ two-phonon gammavibrational bands are obtained with considerable anharmonicity. Reasonably goodagreement, though not perfect, is obtained for both the spectrum and transitionprobabilities with rather small average triaxial deformation $\gamma\approx9^\circ$ for the ground state rotational band. The relation to the wobblingmotion at high-spin states is also briefly discussed.