Spectroscopy ofB9via high-resolution ejectile-tagged recoil break-up

Abstract

An experiment has been carried out using the $^{9}\mathrm{Be}(^{3}\mathrm{He},\phantom{\rule{0.16em}{0ex}}t)^{9}\mathrm{B}^{*}$ reaction at a beam energy of 33 MeV. A large acceptance silicon-strip array was used to detect the $^{9}\mathrm{B}^{*}$ break-up in coincidence with the triton ejectiles in the high-resolution Munich-Q3D spectrograph. The excitation energy regime $<3$ MeV has been explored and the spectrum resulting from proton decaying states, isolated and characterized. Additional resonance strength is observed at 1.86 MeV $\ifmmode\pm\else\textpm\fi{}70$ keV(stat) $\ifmmode\pm\else\textpm\fi{}35$ keV(syst), in agreement with two other recent measurements at higher energies and different angles. The consequences for the ``missing'' ${\textonehalf{}}^{+}$ first excited state are discussed. Additionally, the branching ratios for the 2.36 MeV ${5/2}^{\ensuremath{-}}$ state have been measured as ${\ensuremath{\Gamma}}_{\ensuremath{\alpha}0}/\ensuremath{\Gamma}=0.98\ifmmode\pm\else\textpm\fi{}0.12$ and ${\ensuremath{\Gamma}}_{p0}/\ensuremath{\Gamma}=0.016\ifmmode\pm\else\textpm\fi{}0.008$, in close agreement with earlier work.