Search for Weak Gamma-Rays in the Positron Decay of Mn⁵¹

Abstract

Weak gamma-rays following the decay of Mn⁵¹ were investigated by a NaI(T1) scintillation spectrometer. To eliminate the effect of the strong annihilation gamma-ray, a new method was used. Gamma-rays of 0.74 and 1.17 MeV were found and these intensities were 0.4±0.2 and 0.2±0.1 percent of the positrons, respectively. The half-life of Mn⁵¹ was determined as 44±1 min.