Precise measurement of the half-life of 61 Cu

The decay characteristics of 61Cu allow for a precise determination of its half-life. In order to search for a possible influence of the chemical environment on the decay rate, the half-life of 61Cu in nickel and nickel-oxide was measured with high precision. The results show a small difference in the half-life that can be explained by the differences in electron density at the site of the nucleus. A discussion about the validity of the adopted value of the total angular momentum of the 656keV state in 61Ni is presented.