Rotational Transitions of COH⁺ and He: New Interaction Potential, Bound States, Scattering and Pressure Broadening Cross‐sections**

Abstract

We present new calculations of metastable isomer of HCO+, i.e., COH+ in collision with He. The COH+ has been suggested as an alternative H2 tracer, which makes it of great interest for astrophysical studies. COH+ was first observed in astronomical space towards SgrB2 with observation of J=1→0, J=2→1 and J=3→2 lines. Calculations are based on new ab initio potential energy surfaces (PES) of charged complex COH+‐He using the CCSD(T) in conjunction with aug‐cc‐pVQZ basis set. The PES has well depth of ‐836.5 cm−1 towards H‐end at the COH+−He distance (R) of 2.9 Å in linear orientation. To test the new PES, the calculations of bound‐state are carried out and pressure broadening cross‐sections of COH+ with He collisions are computed for kinetic energies up to 150 cm−1 using accurate close‐coupling method. Further, the pressure broadening and shift coefficients have been calculated from the corresponding real and imaginary parts of cross‐sections for first six rotational transitions. The data obtained is found to be in same order as the HCO+‐He system. Further, the results of rate coefficients are compared with reported COH+‐He and HCO+‐He data. The results generated by this study are believed to be useful for both laboratory and future astrophysical research.