Coulomb excitation of 85Rb and 87Rb

Abstract

Energy levels of 85Rb and 87Rb have been studied via de-excitation γ-rays following Coulomb excitation with 35Cl ions. In addition to the known negative-parity states at 151.2 keV and 868.2 keV in 85Rb, two states at 281.0 keV and 731.8 keV have been found with fourγ-ray transitions of 129.8, 281.0, 450.8 and 731.8 keV. Only one Coulomb excited state at 402.6 keV in 87Rb has been observed. The B(E2↑) values (in units e 2 · b 2) have been determined as 0.0035±0.0004 (151.2 keV), 0.0016±0.0002 (281.0 keV), 0.0101 ±0.0010 (731.8 keV), and 0.036±0.004 (868.2 keV) for the states in 85Rb, and as 0.0054±0.0006 (402.6 keV) for the state in 87Rb. The mean lifetimes of the 731.8 keV and 868.2 keV states have been measured by the Doppler shift attenuation method as 6.4±0.7 psec and 4.2±0.5 psec respectively. Angular distribution measurements allow unique spin and parity assignments of 1 2 − and 3 2 − to the 281.0 keV and 731.8 keV levels respectively. The spin and parity of the 868.2 keV level has been restricted to 5 2 − or 7 2 − .