Electron collision calculations on the BH+ molecular ion for edge plasma applications

Wall conditioning by boronization is used in present-day tokamaks and will also be used in ITER, since it is planned to be a full tungsten machine with boronized walls. With the goal of obtaining collision and molecular data on the BH+ ion, which is expected to be present in the edge plasma due to plasma wall interaction, we have performed detailed calculations on electron collisions with the BH+ ion at its equilibrium geometry Re=2.2755 a0, using the R-matrix method. We have obtained cross sections for electronic excitation from its ground state (X2Σ+) to its first four excited states. For the lowest transition, namely, X 2Σ+→12Π, which has the largest excitation cross section, we have provided an estimate of the vibrationally resolved cross sections and have likewise shown that for this transition, the excitation rates for the isotopologues BD+ and BT+ can be smaller by up to 30% compared to BH+. Cross sections for rotational excitation from the X 2Σ+(j=0) ground state to the rotationally excited states with j′=1,2,3 were obtained in the Coulomb-Born approximation. Estimates of the cross section for the electron impact dissociation have been obtained, and the total ionization cross section of BH+ has been obtained in the Binary Encounter Bethe model. We further report on the bound states of BH, along with many Feshbach resonances and their widths at the BH+ equilibrium. We hope to extend these to more complete diabatic resonance curves in a future work, which may be useful for initiating studies of other processes like dissociative recombination and dissociative excitation.