Recoil-distance measurements of g-factors for 24Mg(2 1+) and 20Ne(2 1+)

Abstract

Time-differential recoil-into-vacuum measurements have been performed with a plunger on the first-excited I π = 2 + states of 24Mg and 20Ne. The states were populated by the reactions 12C( 16O, α) 24Mg and 12C( 12C, α) 20Ne. The measured anisotropy of the α-γ angular correlation was greatly increased by means of a vertical slit on the annular particle detector. Values of ¦g¦= 0.51 ± 0.02 and 0.54 ± 0.04 have been deduced for the 24Mg and 20Ne g-factors, respectively. The mean lives of these states have been determined as τ m = 2.09 ± 0.13 ps and 0.8 ± 0.2 ps, respectively. Various theoretical calculations are discussed and compared with the measured g-factors. The analysis of the measurement also yields values for the populations of electronic states contributing to the hyperfine interaction. For 20Ne the populations of the different electronic configurations are compared with the results of a separate time-integral measurement, in which the correlations were measured for each ionic state separately. Large fractions of two-electron excited states are found to contribute.