Quantification of chemical erosion in fusion edge plasmas is often based upon CH (Gerö-band) spectroscopy. Systematic, vibrationally resolved rate coefficients for the electron impact excitation of A 2Δ, B 2Σ− and C 2Σ+ electronic states of the CH molecule are presented in the temperature range 0.2–1500 eV. The rate coefficients for 0–0 vibrational transitions are based on the R-matrix cross sections for energies below 10 eV, Born–Bethe cross sections for energies above ∼25–30 eV and a smooth interpolation in the 10–20 eV energy range. The rate coefficients for the v–v' transitions are determined by using a scaling relationship. The implications of these results for the fusion edge/divertor plasma diagnostics, based on the A(v') → X(v) transitions, are discussed. The rate coefficients for the 0–0 transitions are presented by convenient analytic fit expressions.
Electron collision cross sections and electronic states of BH: an R-matrix study for fusion edge plasmas