Electron collisions with the CF radicals using the R-matrix method

The R-matrix method is used to treat electron collisions with the diatomic radical CF as a function of internuclear separation, R. These calculations concentrate on obtaining low-energy (< 10 eV) elastic and excitation cross sections of the five lowest-lying electronically excited states of the symmetries X² Π, ⁴ Σ⁻, ² Σ⁺, ²Δ, ² Σ⁻ and ⁴ Π, with vertical excitation energies in the range of 2.86–10 eV. Special measures are required to treat ² Σ⁺, which is Rydberg-like for R < 2.6 a₀. Three shape resonances of ³Σ⁻,¹ Δ and ¹ Σ⁺ symmetries are fitted. The ¹ Δ and ¹ Σ⁺ resonances have a position of 0.91 and 2.19 eV respectively at the equilibrium bond length of CF. The position of the ³ Σ⁻ resonance is close to zero at R_e = 2.44 a₀ and the resonance becomes bound at larger R. Two weakly bound states of symmetries ³Π and ¹ Π were also detected at the equilibrium geometry. Calculations which stretch the C–F bond show that the ¹Δ resonance becomes bound at R = 3.3 a₀ and ¹ Σ⁺ at larger R.