Spectroscopy of ${}^7\mathrm{He}$ states using the ${(}^{15}\mathrm{N}{,}^{17}\mathrm{F})$ reaction on ${}^9\mathrm{Be}$

We have studied states of ${}^7\mathrm{He}$ using the ${}^9\mathrm{Be}{(}^{15}\mathrm{N}{,}^{17}\mathrm{F}{)}^7\mathrm{He}$ reaction at two incident energies, $E_{\mathrm{lab}}=240\mathrm{}$ MeV and 318.5 MeV and observed clearly the first excited state of ${}^7\mathrm{He}.$ An extended study of the three-body background was required to determine the excitation energy and width. The resonance parameters obtained for $l=1\mathrm{}$ are $E_x=2.95\mathrm{}\left(10\right)\mathrm{}$ MeV, and Γ=1.9(3) MeV. There is also evidence of a broad excited state at $E_x=5.8\mathrm{}\left(3\right)\mathrm{}$ MeV with Γ=4(1) MeV. From the analysis of the ${}^7\mathrm{He}$ ground state resonance, we extracted a value of 0.14(2) MeV for the width. In the calibration reaction ${}^{12}\mathrm{C}{(}^{15}\mathrm{N}{,}^{17}\mathrm{F}{)}^{10}\mathrm{Be}$ three high-lying states of ${}^{10}\mathrm{Be}$ are found at 13.6(1), 15.3(2), and 16.9(2) MeV.