Investigation of ${}^{11}$B and ${}^{40}$Ca levels at 8-9 MeV by Nuclear Resonance Fluorescence

Abstract

We report on the measurement of ${}^{11}$B and ${}^{40}$Ca levels between excitation energies of 8 and 9 MeV using nuclear resonance fluorescence (NRF). The experiment was carried out with nearly-monoenergetic and linearly polarized photon beams provided by the High-Intensity $\gamma$-ray Source (HI$\gamma$S) facility at the Triangle Universities Nuclear Laboratory (TUNL). States in ${}^{11}$B are important for calibrations of NRF measurements, while the properties of ${}^{40}$Ca levels impact potassium nucleosynthesis in globular clusters. For ${}^{40}$Ca, we report on improved excitation energies and an unambiguous $2^{-}$ assignment for the state at 8425 keV. For ${}^{11}$B, we obtained improved values for $\gamma$-ray multipolarity mixing ratios and branching ratios of the 8920 keV level.

14 pages, 9 figures, to be published in Physical Review C

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