The decay of mass-separated ¹⁹⁹P0

Mass-separated sources of ¹⁹⁹ Po were produced through the reaction ¹⁹¹Ir(¹⁴N,6n). Energies and intensities were meaured for both y-rays and conversion electrons. On-line multiscale data were used to determine half-lives of many transitions. From an analysis of the Y-y-t coincicidence data and energy sums, 33 transitions were placed in a decay scheme between 29 levels in 199. Bi. Spin and parity assignments were made on the basis of measured conversion coefficients. An unusually large retardation was determined for decay from the ½⁺ isomeric state to ¹⁹⁹ Bi. The rate for this transition was at least 38o times less than the Weisskopf estimate of the single particle rate. Decay observed from the 13/2* isomeric level in ¹⁹⁹ Po made possible the placement of the 13/2⁺ and 5/2^- levels above the 3/2^- ground state. A branching ratio of 2.1% was determined for the M4 transition from the 13/2^- state. A retardation factor of O.58 Weisskopf units was determined for this transition. The placement of the 13/2⁺; state in ¹⁹⁹ Po together with α-decay information made possible the location of the 13/2⁺; isomeric state in ¹⁹⁵ pb.