K40(n,γ)K41Reaction and the Level Structure ofK41

The low-lying level structure of ${}_{}{}^{41}{}_{}{}^{}\mathrm{K}$ has been studied using the thermal-neutron capture reaction ${}_{}{}^{40}{}_{}{}^{}\mathrm{K}(n,\gamma ){}_{}{}^{41}{}_{}{}^{}\mathrm{K}$ on an isotopically separated target of ${}_{}{}^{40}{}_{}{}^{}\mathrm{K}$. The $\gamma$-ray spectrum from this reaction has been studied in the energy range from 0.1 to 10.1 MeV using a Li-drifted Ge spectrometer system. $\gamma -\gamma$ coincidence measurements using Ge(Li) detectors have also been made. Spin and parity assignments for the excited states below 2450 keV are proposed, primarily on the basis of $\gamma$-ray branching to levels with established spin and parity values. The proposed level energy [keV ($I^{\pi }$)] values are $0\left({\frac{3}{2}}^{+}\right)$, $980.4\left({\frac{1}{2}}^{+}\right)$, $1293.4\left({\frac{7}{2}}^{-}\right)$, $1559.9\left({\frac{1}{2}}^{+}\right)$, $1582.0\left({\frac{5}{2}}^{+}\right)$, $1677.5({\frac{5}{2}}^{+},{\frac{7}{2}}^{+})$, $1698.1({\frac{5}{2}}^{\pm },{\frac{7}{2}}^{+})$, $2144.1\left({\frac{5}{2}}^{+}\right)$, $2166.0({\frac{1}{2}}^{+},{\frac{3}{2}}^{\pm })$, $2316.5({\frac{5}{2}}^{+},{\frac{7}{2}}^{+})$, $2447.9({\frac{1}{2}}^{\pm },{\frac{3}{2}}^{\pm })$. Additional levels have been observed at 2494.7, 2507.9, 2527.9, 2599.8, 2681.5, 2712.2, 2756.5, 2760.7, 3042.1, 3142.1, 3164.5, 3213.4, 3235.6, and 3281.1 keV. These low-lying excited states of