Messung der Lebensdauer des 287 keV-Zustands im⁷⁵Se

Abstract

The nuclear half-life of the 287 keV second excited state of⁷⁵Se, populated by the reaction⁷⁵As(p, n)⁷⁵Se^* has been measured by the delayed coincidence technique. NaJ(Tl)- and Ge(Li)-detectors were used for measuringγ-energies and time-spectra. By slope analysis of the time-spectra we obtained a half-life of T_1/2(⁷⁵Se, 287 keV)=(30.0±0.4) ns. Possible spin assignments for the 287 keV state in⁷⁵Se from logft-values derived fromβ ⁺-decay data of⁷⁵Br to this level byBaskova et al are 3/2⁻ and 1/2⁻.

Application of an external magnetic field of 24 kG to the target nuclei yielded no measurable perturbation of the time-spectra, thus a spin value of 1/2⁻ for this level seems to be more probable.