E2M1multipole mixing ratios of2′→2gamma transitions in even-even spherical nuclei

Abstract

A systematic survey is presented of $\frac{E2}{M1}$ mixing ratios of $\ensuremath{\gamma}$ transitions between the ${2}^{+}$\ensuremath{'} and ${2}^{+}$ levels of even-even nuclei in the mass range $58\ensuremath{\le}A\ensuremath{\le}152$. Particular attention is given to the variations in the phase of the mixing ratios, which are deduced from the literature in a systematic manner. It is shown that the systematics of both magnitudes and phases of the mixing ratios are explained quite well for a number of nuclei by a model proposed by Greiner, in which the magnitude of the mixing ratio is parametrized in terms of the deviation of the $g$ factor of the first ${2}^{+}$ state from the value $\frac{Z}{A}$. It is further shown that a semimicroscopic description, in terms of small admixtures of two-particle components to the phonon basis states, yields reasonable agreement with the observed phase variations and absolute magnitudes, even when only very few two-particle states are considered.NUCLEAR STRUCTURE $^{58,\phantom{\rule{0ex}{0ex}}60,\phantom{\rule{0ex}{0ex}}62}\mathrm{Ni}$, $^{64,\phantom{\rule{0ex}{0ex}}66,\phantom{\rule{0ex}{0ex}}68}\mathrm{Zn}$, $^{70,\phantom{\rule{0ex}{0ex}}72,\phantom{\rule{0ex}{0ex}}74,\phantom{\rule{0ex}{0ex}}76}\mathrm{Ge}$, $^{74,\phantom{\rule{0ex}{0ex}}76,\phantom{\rule{0ex}{0ex}}78}\mathrm{Se}$, $^{80,\phantom{\rule{0ex}{0ex}}82,\phantom{\rule{0ex}{0ex}}84}\mathrm{Kr}$, $^{84,\phantom{\rule{0ex}{0ex}}86,\phantom{\rule{0ex}{0ex}}88}\mathrm{Sr}$, $^{92}\mathrm{Zr}$, $^{94,\phantom{\rule{0ex}{0ex}}96,\phantom{\rule{0ex}{0ex}}98}\mathrm{Mo}$, $^{100,\phantom{\rule{0ex}{0ex}}102,\phantom{\rule{0ex}{0ex}}104}\mathrm{Ru}$, $^{104,\phantom{\rule{0ex}{0ex}}106,\phantom{\rule{0ex}{0ex}}110}\mathrm{Pd}$, $^{106,\phantom{\rule{0ex}{0ex}}108,\phantom{\rule{0ex}{0ex}}110,\phantom{\rule{0ex}{0ex}}112,\phantom{\rule{0ex}{0ex}}114,\phantom{\rule{0ex}{0ex}}116}\mathrm{Cd}$, $^{116}\mathrm{Sn}$, $^{122,\phantom{\rule{0ex}{0ex}}124,\phantom{\rule{0ex}{0ex}}126}\mathrm{Te}$, $^{126,\phantom{\rule{0ex}{0ex}}128,\phantom{\rule{0ex}{0ex}}132}\mathrm{Xe}$, $^{132,\phantom{\rule{0ex}{0ex}}134}\mathrm{Ba}$, $^{140,\phantom{\rule{0ex}{0ex}}142}\mathrm{Ce}$, $^{144}\mathrm{Nd}$, $^{150}\mathrm{Sm}$, $^{152}\mathrm{Gd}$; calculated $\frac{E2}{M1}$ mixing ratio $\ensuremath{\delta}$.