Ground-State Quasirotational Bands and Other States inCe130,132,134,136,138,140

Abstract

The even cerium isotopes 130 through 140 have been investigated by $\mathrm{Ba}(\alpha , \mathrm{xn}\gamma )\mathrm{Ce}$. The energies, relative intensities, angular distributions, and time distributions of the $\gamma$ rays relative to the cyclotron beam bunch have been measured. The results show transitions from states up to $8^{+}$ in ${}_{}{}^{130}{}_{}{}^{}\mathrm{Ce}$ (253.2, 456.4, 613.9, and 729.0 keV ±1 keV), up to ${10}^{+}$ in ${}_{}{}^{132}{}_{}{}^{}\mathrm{Ce}$ (325.6, 533.5, 684.5, 789.0, and 875 keV), and up to $8^{+}$ in ${}_{}{}^{134}{}_{}{}^{}\mathrm{Ce}$ (409.4, 639.9, 814.8, and 947 keV). Several transitions from states not in the ground-state band have been assigned in the three heaviest isotopes. The most prominent transitions (ground-state band; others) are for ${}_{}{}^{136}{}_{}{}^{}\mathrm{Ce}$: 551.7, 761.7, 898.8; 328.6, 623.6, 664.3, and 1051.9 keV; for ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ce}$: 787.9, 1037.4; 302.1, 390.7, 402.8, 417.5, 430.1, and 815.0 keV; and for ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}$: 1596.7, 486.7, 202.0, 222.0, 1317.5, and 1404.1 keV. A 22-nsec level is found in ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}$. Significant long-lived (≳200 nsec) feeding of the ground-state band has been observed in each Ce isotope.