Lifetime Measurements Of Excited States In Cr-55

Excited states in Cr-55 have been populated via the fusion-evaporation reaction Ca-48(B-11, p3n) Cr-55 at a beam energy of 32 MeV. The Cologne plunger device surrounded by a gamma-ray detector array was employed to determine lifetimes with the recoil-distance Doppler-shift method. gamma rays were observed by one Ge EUROBALL cluster detector and five HPGe detectors. gamma gamma-coincidence data were analyzed with help from the differential decay-curve method, and precise lifetimes for the first excited states were extracted from the 5/2(-) -> 3/2(-) and the 9/2(-) -> 5/2(-) transitions. Reduced transition strengths B(sigma lambda) were determined and compared to shell-model calculations employing four interactions KB3G, FPD6, GXPF1A, and GXPF1Br. The calculations were also performed for the N = 31 isotonic chain from Ti-53 to Zn-61. Inspection of the wave functions as well as particle-plus-rotor model calculations allow for a detailed understanding of the excited states and the reduced transition strength in Cr-55.