Beta-gamma directional correlation in Sb 124

Abstract

The directional correlation between the non-unique first-forbidden outer beta group of endpoint energy 2.31 MeV in Sb 124 and the 0.603 MeV cascade gamma ray in Te 124 has been measured at twenty six beta energies. The measured beta-gamma correlation coefficient ϵ ranges from −(0.186±0.016) to −(0.387±0.010) in the beta energy interval 0.95 to 2.20 MeV. Taking into account the existing data on shape correction factor and also the angular dependence of the beta gamma circular polarization coefficient ω, the relevant first-forbidden beta decay matrix element ratios have been extracted; the ratios of the matrix elements are (in Kotani's notation) x = 0.06±0.05, u = 0.15±0.05 and Y = 1.05±0.15. Absolute values of the matrix elements were obtained from the observed log ft value as |∫ B ij |/ R = (1.0±0.2) × 10 −2, |∫ r|/R = (7.5±6.4) × 10 −4 , |∫ i σ × r|/R = (15.5±5.9) × 10 −4 , |∫ i α| = (7.0±2.1) × 10 −4 . The experimental ratio of ∫ iα/∫ r agrees with the predictiction of the conserved vector current theory of beta decay.