State-to-state electron impact cross sections for BeH+ molecular ions in ITER-like fusion edge plasmas with Be walls

Abstract

BeH+ molecules will be an important intermediary species present in fusion plasmas with Be walls (e.g. JET, ITER), both for impurity transport and spectroscopic studies. To enable such analyses the electron-impact-induced excitations X 1Σ+(vi) → A 1Σ+(vf) and X 1Σ+(vi) → B 1Π(vf) in BeH+(vi) molecular ion, occurring between the vi and vf vibrational levels of different electronic states (vibro-electronic transitions), have been studied using the Coulomb–Born approximation. The cross sections and rate coefficients for these transitions have been calculated in a broad energy and temperature range, respectively. Accurate analytic fit expressions have been derived for the cross sections and rate coefficients for the vi = vf = 0 case of considered electronic transitions that have correct asymptotic limits. It has been demonstrated that the cross sections and rate coefficients for vi, vf > 0 transitions satisfy approximate (to within 10%) scaling relationships that involve the transition energies and matrix elements of dipole transition moments only.