Lifetime Measurements from theK39(p,γ)Ca40Reaction

Abstract

Lifetime measurements with a Ge(Li) detector have been made for several excited states of ${\mathrm{Ca}}^{40}$ by the Doppler-shift attenuation method utilizing the ${\mathrm{K}}^{39}(p,\ensuremath{\gamma}){\mathrm{Ca}}^{40}$ reaction. Agreement with results of ($p,{p}^{\ensuremath{'}}\ensuremath{\gamma}$) lifetime measurements is found for levels at 3.904, 5.280, and 6.285 MeV. New lifetime results are reported for levels at 5.615 MeV (>0.8 psec), 7.465 MeV ($0.010_{\ensuremath{-}0.006}^{}{}_{}{}^{+0.005}$ psec), and 7.562 MeV ($0.26_{\ensuremath{-}0.07}^{}{}_{}{}^{+0.14}$ psec. An upper limit of 1% is set for the branching of the 3.904-MeV (${2}^{+}$) to the 3.354-MeV (${0}^{+}$) levels. Comparison is made with Gerace and Green's predictions that the 5.280-, 3.904-, and 3.354-MeV levels form a rotational band. Calibration of the resonance spectrum with ${\mathrm{Co}}^{56}$ $\ensuremath{\gamma}$ rays has resulted in precise establishment of level energies for ${\mathrm{Ca}}^{40}$, a better $Q$ value for the reaction of 8.3295\ifmmode\pm\else\textpm\fi{}0.0009 MeV, and the association of the lower member of the doublet near 5.615 MeV with the ${4}^{\ensuremath{-}}$ level in this region. New decay modes are established for the levels at 7.113, 7.562, and 7.811 MeV.