Electron collision cross sections and electronic states of BH: an R-matrix study for fusion edge plasmas

A detailed collision calculation of electron impact on BH at the BH equilibrium $R_e=2.3285$\bohr\ is presented. First a good quality wave function for the target BH molecule is developed at the configuration interaction level. Then the R-matrix method is used to obtain collision cross sections for elastic scattering and state-to-state excitation to several excited electronic states of BH. The differential cross sections for elastic scattering below 10 eV and momentum transfer cross section are also obtained. Our calculations further yield two BH$^-$ anionic bound states and a few e-BH anionic resonances which have not been previously reported. We obtain potential energy curves for the two BH$^-$ bound states of $^2\Pi$ and $^4\Sigma^-$ symmetries, and the potential energy curve for the resonant BH$^-$ state of $^2\Pi$ symmetry. These data will aid studies of edge plasma characteristics in tokamaks where boronization is used for wall conditioning.