| Abstract | The potential energy surface and dipole moment surfaces of the ã⁴A2 electronic state of CH+2 are calculated ab initio using an augmented correlation-consistent polarized valence quadruple-ζ (aug-cc-pVQZ) basis set, with the incorporation of dynamical correlation using the coupled cluster method with single and double excitations and perturbatively connected triple excitations [CCSD(T)]. We use these surfaces in the MORBID program system to calculate rotation and rotation–vibration term values for ã-state CH+2 , CD+2 , and CHD+ and to simulate the rotation and rotation–vibration absorption spectrum of CH+2 in the ã⁴A2 electronic state. Our work is motivated by studies of CH+2 that use the Coulomb explosion imaging technique and by the goal of predicting spectra that may be obtained from discharge sources. Although the ˜ a state is the lowest-lying excited state above the ˜X / ˜A ground state pair, it turns out to be relatively high-lying, and we determine that Te( ã) = 30447.5 cm−1. The equilibrium bond angle for ã-state CH+2 is only 77.1◦; as a result the asymmetric top κ value is close to 0, and the molecule is equally far from the oblate and prolate symmetric top limits in this electronic state. |
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