Beta +-electron-capture decay of 69Se.

Abstract

The ${\ensuremath{\beta}}^{+}$--electron-capture decay of $^{69}\mathrm{Se}$, produced via the $^{40}\mathrm{Ca}$${(}^{32}$S, 2pn${)}^{69}$Se reaction, has been studied by \ensuremath{\beta}-delayed proton and \ensuremath{\gamma}-ray emissions using the recoil transport helium jet technique. The established decay scheme for $^{69}\mathrm{Se}$ involves 13 up to now unreported \ensuremath{\gamma} emitting levels in $^{69}\mathrm{As}$. The total proton branching ratio has been measured to be (4.5\ifmmode\pm\else\textpm\fi{}1.0)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$. The autocorrelation analysis of the delayed proton spectra indicates a level spacing in agreement with the back shifted Fermi gas model estimates. The Gamow-Teller beta strength distribution has been measured in 95% of the ${Q}_{\ensuremath{\beta}}$ window, up to 6.5 MeV excitation energy in $^{69}\mathrm{As}$.