Spectroscopy and lifetime measurements of states in 76Kr populated in 76Rb decay

Abstract

The properties of the excited states of Kr-76, populated in the decay of Rb-76 produced at ISOLDE isotopic separator, have been investigated by using K-conversion electron, gamma-ray, and gamma-gamma coincidence measurements. The lifetimes of several levels have been measured by means of the advanced time-delayed beta gamma gamma(t) method. The identification of 19 new levels and 55 transitions and the information deduced on spin and/or parity of the observed states from K-conversion coefficients, log ft values and decay properties have led to an improved knowledge of the level scheme. In particular, six 1(-) states have been definitely identified and J(pi)=2(-) has been assigned to the 2227 keV level, on which a band proposed to have negative-parity and even-spin had been previously observed. The strengths of the E0 and E2 transitions deexciting the 0(2)(+) and 0(3)(+) states (the latter is here identified with the state at 1598 keV) have been measured. The experimental data concerning the 0(2)(+) state have been analyzed in a simple two states mixing model and in the framework of the proton-neutron interacting boson model.