Hole States inNe19

Abstract

Levels of ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$ below an excitation energy of 7 MeV have been investigated using the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}({}_{}{}^3{}_{}{}^{}\mathrm{He},\alpha ){}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$ reaction at a bombarding energy of 15 MeV. Previously unreported states of ${}_{}{}^{19}{}_{}{}^{}\mathrm{Ne}$ were observed at excitation energies of 4.200, 4.625, 4.783, 5.351, 5.426, 5.463, 5.545, 5.831, 6.012, 6.089, 6.149, 6.290, 6.433, 6.744, 6.866, and 7.064 MeV. Angular distributions of strongly excited states are compared with distorted-wave Born-approximation calculations. The ground state and a state at 5.351 MeV have angular distributions characteristic of $l=0\mathrm{}$ neutron pickup whereas states at 0.273, 1.615, 4.551, 6.012, and 6.744 MeV correspond to $l=1\mathrm{}$ neutron pickup, and states at 0.238, 1.54, and 4.036 MeV correspond to $l=2\mathrm{}$ neutron pickup. The following new spin and parity assignments are made: 1.51, (${\frac{5}{2}}^{-}$); 1.54, ${\left(\frac{3}{2}\right)}^{+}$; 1.615, ${\left(\frac{3}{2}\right)}^{-}$; 4.036, ${\frac{3}{2}}^{+}$, (${\frac{5}{2}}^{+}$); 4.551, ${\frac{1}{2}}^{-}$, ${\frac{3}{2}}^{-}$; 5.351, ${\frac{1}{2}}^{+}$; 6.012, ${\frac{3}{2}}^{-}$, (${\frac{1}{2}}^{-}$); 6.744, ${\frac{3}{2}}^{-}$, (${\frac{1}{2}}^{-}$); energies in MeV. Relative spectroscopic factors are extracted and are compared with predicted configurations of negative-parity states in mass-19 nuclei and with the predicted ground-state neutron configuration of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$. Analog states in the mirror nucleus, ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$, are discussed.