Doubly excited states in electron-impact ionization ofC3+ions

Resonances due to a resonant-excitation–double-autoionization process in the electron-impact ionization of ${\mathrm{C}}^{3+}$ ions are calculated using the R-matrix method. Twelve autoionizing states arising from the 1s2${\mathit{s}}^2$, 1s2s2p, 1s2${\mathit{p}}^2$, 1s2s3s, 1s2s3p configurations, together with the ground 1${\mathit{s}}^2$2${\mathit{s}}^2$S and excited 1${\mathit{s}}^2$2p ${}_{}{}^2{}_{}{}^{}$ ${\mathit{P}}^0$, 1${\mathit{s}}^2$3${\mathit{s}}^2$S, 1${\mathit{s}}^2$3p ${}_{}{}^2{}_{}{}^{}$ ${\mathit{P}}^0$, 1${\mathit{s}}^2$3d ${}_{}{}^2{}_{}{}^{}$D states, are included in the close-coupling expansion. These states are represented by accurate configuration-interaction wave functions. The present results are in good agreement with the recent crossed-beam measurement.