Nuclear lifetimes inAr42

Abstract

Excitation energies and nuclear lifetimes of states in $^{42}\mathrm{Ar}$ have been measured by employing the reaction $^{40}\mathrm{Ar}(t,p)^{42}\mathrm{Ar}$ at a triton bombarding energy of 2.8 MeV. Protons were detected by an annular silicon surface barrier counter at an average angle of 174\ifmmode^\circ\else\textdegree\fi{}, and coincident $\ensuremath{\gamma}$ rays were detected by a 20-cm$^{3}\mathrm{Ge}$(Li) counter positioned at angles of 30 and 120\ifmmode^\circ\else\textdegree\fi{}. The extraction of nuclear lifetimes by the Doppler-shift-attenuation technique was made possible by the use of a solid argon target operated at 15 K. Experimental results for excitation energies (keV) and lifetimes (psec) are: 1208.2\ifmmode\pm\else\textpm\fi{}0.3, ${3.8}_{\ensuremath{-}0.8}^{+1.0}$; 2486.7\ifmmode\pm\else\textpm\fi{}0.6, 0.40\ifmmode\pm\else\textpm\fi{}0.16; 2512.5\ifmmode\pm\else\textpm\fi{}0.5, ${4.0}_{\ensuremath{-}1.2}^{+3.1}$; 3014.6\ifmmode\pm\else\textpm\fi{}0.6, 0.12; 3096.4\ifmmode\pm\else\textpm\fi{}0.6, >5; 3557.8\ifmmode\pm\else\textpm\fi{}0.6, 0.09; 4006.1\ifmmode\pm\else\textpm\fi{}0.6, 3.3\ifmmode\pm\else\textpm\fi{}0.8; 4127.4\ifmmode\pm\else\textpm\fi{}0.7, 1.4\ifmmode\pm\else\textpm\fi{}0.3; 4287.0\ifmmode\pm\else\textpm\fi{}0.7, 0.05; 4633.7\ifmmode\pm\else\textpm\fi{}0.7, 0.05. The experimental results are in good agreement with the shell-model calculations of Gloeckner, Lawson, and Serduke.[NUCLEAR REACTIONS $^{40}\mathrm{Ar}(t,p)$, ${E}_{t}=2.8$ MeV; measured $\ensuremath{\sigma}({E}_{p},{E}_{\ensuremath{\gamma}},{\ensuremath{\theta}}_{\ensuremath{\gamma}})$. $^{42}\mathrm{Ar}$ deduced ${E}_{x}$, ${I}_{\ensuremath{\gamma}}$, ${\ensuremath{\tau}}_{m}$. Solid Ar target; Doppler shift attenuation.]