Levels and transition rates in 199Au

Abstract

The decay of 199Pt to 199Au (T 1 2 = 30.8 min) has been investigated using a Ge(Li) detector and a double focussing beta spectrometer. 34 transitions were found and multipolarities were assigned for 11 of these, including a 55.15 keV M2+(0.9±0.5)%E3 isometric transition. Using these data together with the results of γ-γ and β-γ coincidence measurements, a decay scheme containing 9 excited levels and 25 transitions was constructed and spin and parity assignments were made. Using the delayed coincidence technique half-lives were determined for 3 levels and upper limits were obtained for 5 additional levels. The following levels were found: 77.21±0.03 keV ( 1 2 +, 1.1±0.1 ns); 316.98±0.10 ( 5 2 +, < 55 ps); 323.57±0.09 keV (( 1 2 ), 3 2 +, 35±20 ps); 493.59±0.10 keV ( 7 2 +, < 35 ps); 542.82±0.07 keV ( 5 2 +, < 30 ps); 548.65±0.09 keV ( 11 2 −); 734.44±0.11 keV ( 7 2 −, 0.36±0.04 ns); 791.47±0.15 keV ( 3 2 +, 5 2 +, < 50 ps); and 967.98±0.20 keV ( 3 2 (+), 5 2 (+), < 100 ps) . The decay properties of the lowest excited positive parity levels are discussed in terms of de-Shalit's core excitation model.