Lifetime measurements in 72 As

Available as short communication only. Recently, the levels in 72 As have been studied employing the 59 Co (16 O, 2 p n) 72 As reaction with the Bucharest tandem and the 47 Ti (28 Si, 3 p) 72 As with the HHIRF tandem to enhance the population of high spin states. New states were observed about the 563.3 keV, J=7- isomer forming a high-spin sequence of levels based on a J=8+ level at 981.6 keV excitation energy. Recently, calculations on the VAMPIR models were extended to include proton-neutron as well as parity-mixing and complex HFB transformations so that states with arbitrary spin and parity in even-even and odd-odd nuclei could be treated. This possibility to describe the spectra of odd-odd nuclei with the same microscopic methods as the doubly even ones was used for the first time in this mass region for 72 As; as in neighboring doubly even nuclei also here coexisting bands based on intrinsic structures with opposite quadrupole deformations were found. The matrix elements for electromagnetic transitions are required to test the theoretical predictions; evidently, electric quadrupole electromagnetic elements are appropriate to test collective aspects. Since except for the 432.6 keV gamma ray there is no evidence for Doppler broadening in the angular distributions or gamma-gamma coincidences lifetimes were measured via the recoil distance method using the 56 Fe (19 F, 2 p n) 72 As reaction at 60 MeV bombarding energy. The data analysis is in progress. (Author) 2 Refs