Excited states and transitions in 199Au

Abstract

Gamma radiations and conversion electrons in the decay of 31 min 199Pt to 199Au have been investigated by using Ge(Li) detectors and a Si-Ge(Li) conversion coefficient spectrometer. Thirty-nine gamma-ray lines were observed, including ten unreported lines. New levels have been confirmed at 822.3 ± 0.5, 1069.6 ± 0.5, 1103.2 ± 0.3, 1158.7 ± 0.5, 1249.0 ± 0.4and 1395.6 ± 0.5 keV on the basis of NaI(Tl)-Ge(Li) coincidence measurements. The spin and parity of the 791.4 keV level were determined as 3 2 + from the M1 character of the 714.1 keV transition. Angular correlations of four gamma-ray cascades of 191.7–542.7, 468.0–246.5, 474.5–317.0 and 714.1–77.1 keV have been measured. The results are consistent with the spin assignments of 1 2 and 3 2 to the 77.1 and 323.6 keV levels respectively, the 1 2 assignment to the latter level being excluded. From the measured conversion coefficients and angular correlation coefficients, the following M1-E2 mixing ratios have been determined: 317.0 keV, M1 + (25 ± 10) % E2; 468.0 keV, M1 + < 37%E2; 474.5 keV, M1 + (1.4 ± 0.4) % E2; 542.7 keV, M1 + (0.3 +2.0 −0.3) % E2; 714.1 keV, M1 + < 52 % E2. The energy level spectrum obtained is compared with the theoretically calculated one based on the intermediate coupling model. The transition probabilities of the lower excited states are compared with theoretical predictions based on three different models.