Structure of ${}^{14}$B and the evolution of $N=9$ single-neutron isotones

We have used the ${}^{13}$B($d,p$)${}^{14}$B reaction in inverse kinematics to study the properties of states in ${}^{14}$B, the lightest particle-bound $N=9$ isotone. The spectroscopic information, including spins, parities, and spectroscopic factors for the states observed in ${}^{14}$B are used to deduce the wave functions for the low-lying negative parity $\nu \left(\mathit{sd}\right)$ levels, as well as provide information about the evolution of the effective neutron $1s_{1/2}-0d_{5/2}$ single-particle energies. The data confirm that the ground and first-excited states are predominantly $s$ wave in character and are single-neutron halo states. The effective single-particle energies are found to match the trends set by other $N=9$ isotones.

Figure 1

${}^{14}$B excitation-energy spectrum from the ${}^{13}$B${(d,p)}^{14}$B reaction. The filled (open) histogram corresponds to protons detected in coincidence with identified ${}^{14}$B(${}^{13}$B) recoil ions. The vertical dashed line shows the neutron-separation energy, and the cross-hatched peak is described in the text. The inset shows the level diagram for ${}^{14}$B from [4].

Figure 2

Angular distributions for different states in the ${}^{13}$B($d,p$)${}^{14}$B reaction. The horizontal bars represent the angular range for each data point. The curves represent DWBA calculations described in the text, with the thick-dashed, dot-dashed, and solid curves corresponding to $\ell =0$, 2, and $0+2$, respectively. The thin-dashed curve in (a) shows the $\ell =0$ result for the 2${}_1^{-}$ state before averaging over the scattering angle.

Figure 3

Effective single-particle binding energies of the $1s_{1/2}$ and $0d_{5/2}$ orbitals as a function of $Z$, for $N=9$ isotones. The ${}^{14}$B points are from the present measurement, and the lines are to guide the eye.