E2 and M1 transition probabilities between low-energy states in 189Ir

Abstract

Half-lives have been measured for the lowest excited states in 189Ir and the transitions between the states have been studied using high-resolution electron and γ-spectroscopy. The following half-lives were obtained: 94.34 keV, 11.6±0.6 nsec; 113.82 keV, 76±18 psec; 176.53 keV, 22±10 psec; 300.51 keV, < 20 psec. A new transition was found at 62.65 keV. From L Subshell ratios the following multipolarity mixtures were obtained: 62.65 keV, M1 + (8.5 −3 +6 % E2; 71.69 keV, M2; 82.22 keV, M1 + (2.8±0.7) % E2; 94.34 keV, E2 + (5.5±1.0) % M1; 113.82 keV, M1 + (23±2)% E2; 141.18 keV, M1 + (1.5 +1.5 −0.8) % E2; 176.53 keV, M1 + (44±3) % E2; 186.70 keV, M1 + (21±4) % E2; 203.78 keV, M1 + < 30% E2; 223.34 keV, E2; 243.50 keV, E2; 258.37 keV, E3; 300.51 keV, E2; 317.65 keV, M1 + (23±10) % E2. Reduced E2 and M1 transition probabilities are calculated and compared to the result of a two-band Coriolis coupling calculation. A deformation parameter δ = 0.23 is obtained in 189Ir. This represents a sharp increase from the value δ = 0.12 obtained in 191Ir and 193Ir. The B(E2) and B(M1) values in all odd- AIr nuclei are presented systematically and compared to current nuclear models.