Coriolis coupling effects in proton-pickup spectroscopic factors from ${}^{12}\mathrm{B}$

Spectroscopic factors to low-lying negative-parity states in ${}^{11}\mathrm{Be}$ extracted from the ${}^{12}\mathrm{B}(d,{}^3\mathrm{He}){}^{11}\mathrm{Be}$ proton-removal reaction are interpreted within the rotational model. Earlier predictions of the $p$-wave proton-removal strengths in the strong-coupling limit of the Nilsson model underestimated the spectroscopic factors to the $3/2_1^{-}$ and $5/2_1^{-}$ states and suggested that deviations in the $1^{+}$ ground state of the odd-odd ${}^{12}\mathrm{B}$ due to Coriolis coupling should be further explored. In this work we use the particle rotor model to take into account these effects and obtain a good description of the level scheme in ${}^{11}\mathrm{B}$, with a moderate $K$ mixing of the proton Nilsson levels [110]1/2 and [101]3/2. This mixing, present in the $1^{+}$ bandhead of ${}^{12}\mathrm{B}$, is key to explaining the proton-pickup data.

Figure 1

Nilsson levels relevant for the structure of negative-parity neutron states in ${}^{11}\mathrm{Be}$ and ${}^{11}\mathrm{B}$ (solid lines). Also shown (dashed lines) are the levels originating from the $d_{5/2}$ spherical orbital. The shaded band indicates the anticipated range of ${\epsilon }_2$ deformation for these nuclei and the horizontal lines indicate the approximate Fermi levels of the odd neutron (blue) and the odd proton (red). Energies are in units of the harmonic oscillator frequency, $\hslash {\omega }_0$.

Figure 2

Left: The experimental level scheme of ${}^{11}\mathrm{B}$ from Ref. [3]. Right: Results of the PRM calculations. Energies are in keV.