Ab initio potential energy curves and transition dipole moments for the low-lying states of CH+

Radiative association of C(3P) and H+: triplet states

“…Our calculated TDMs are shown in Fig. 2 for the triplet transitions of interest and they are in good agreement with those calculated by others using the MRCISD method (Stancil et al 1998a;Biglari et al 2014), where available. The TDM connecting the b 3 Σ − state to the d 3 Π state is not available, evidently, in the literature and we list our calculated values in Table 2.…”

“…6, are very small due to limited Franck-Condon overlap. Levels of the b 3 Σ − state are predissociated by the c 3 Σ + state for v > ∼ 4, see Hechtfischer et al (2007) for a detailed analysis, and the probability of forming levels with v < ∼ 4, which would decay to the a 3 Π state (Biglari et al 2014), is small. We ignored predissociation and radiative cascading and estimated the cross sections using the quantum-mechanical approach, Eq.…”

R-matrix study of electron impact excitation and dissociation of CH+ions

“…We have tested different target models, a summary of which is presented in Table 1. Finally, target model 5 with an extended (1σ) 2 (2 − 8σ, 1 − 3π, 1δ) 4 CAS was chosen as it gave the best agreement in terms of excitation energies and dipole moments with the coupled cluster singles doubles and triples (CCSDT) calculations of Kowalski & Piecuch (2001) and the multi reference configuration interaction (MRCI) calculation of Biglari et al (2014). Figure 1 shows the behaviour of the lowest 9 CH + target potential energy curves (PECs).…”

“…Figure 1 shows the behaviour of the lowest 9 CH + target potential energy curves (PECs). Shown also are the corresponding PECs obtained by Biglari et al (2014). In Figure 1 we have shifted the R-matrix curves down by 1.28 eV so that the two sets of curves have the same minima of the X 1 Σ + ground state.…”

“…Below A Figure 2 shows the vibrationally-resolved electronic-excitation cross sections from the X 1 Σ + vibrational ground states to the a 3 Π, A 1 Π and b 3 Σ − excited states, the vibrational state ν ′ being indicated in each panel. To calculate the vibrationally resolved cross sections we first calculated Franck-Condon factors corresponding to the transitions from the a 3 Π, A 1 Π and b 3 Σ − states to the X 1 Σ + state with the potential energy curves of Biglari et al (2014) using Le Roy's LEVEL program (Le Roy 2017), and these are presented in Table 6. At least for the A 1 Π → X 1 Σ + transitions, these are in good agreement to within 10% of the Franck-Condon factors computed with more accurate potential energy curves (Hakalla et al 2006).…”