K-shell photoionization of ground-state Li-like boron ions [B${}^{2+}$]: Experiment and Theory

Absolute cross sections for the K-shell photoionization of ground-state Li-like boron [B${}^{2+}$(1s${}^2$2s ${}^2$S)] ions were measured by employing the ion-photon merged-beams technique at the Advanced Light Source synchrotron radiation facility. The energy ranges 197.5–200.5 eV, 201.9–202.1 eV of the [1s(2s,2p)${}^3$P]${}^2$P${}^{\mathrm{o}}$ and [1s(2s,2p)${}^1$P] ${}^2$P${}^{\mathrm{o}}$ resonances, respectively, were investigated using resolving powers of up to 17,600. The energy range of the experiments was extended to about 238.2 eV yielding energies of the most prominent [1s(2$\mathrm{\ell }$,n${\mathrm{\ell }}^{\mathrm{\prime }}$)]${}^2$P${}^o$ resonances with an absolute accuracy of the order of 130 ppm. The natural linewidths of the [1s(2s,2p)${}^3$P] ${}^2$P${}^{\mathrm{o}}$ and [1s(2s,2p)${}^1$P] ${}^2$P${}^{\mathrm{o}}$ resonances were measured to be $4.8\pm 0.6$ meV and $29.7\pm 2.5$ meV, respectively, which compare favourably with theoretical results of 4.40 meV and 30.53 meV determined using an intermediate coupling R-matrix method.