Electronic spectroscopy of carbon chains (C2n+1, n = 7–10) of astrophysical importance. II. Quantum dynamics.

In continuation with Paper I [S. R. Reddy et al., J. Chem. Phys. 151, 054303 (2019)], the vibronic structure and dynamics of the 1 Σ u + electronic state of C₁₅, C₁₇, C₁₉, and C₂₁ chains in the coupled manifold of 1 Σ u + –¹Π_g–¹Π_u– 1 Σ g + electronic states have been investigated in this paper. The model vibronic Hamiltonian developed through extensive ab initio quantum chemistry calculations in Paper I is employed, and first principles nuclear dynamics calculations are carried out to obtain the photoabsorption band of the 1 Σ u + electronic state. Both time-independent and time-dependent quantum mechanical calculations are carried out to precisely locate the vibrational levels, assign them with the progression of vibrational modes, and elucidate the impact of both Renner-Teller and pseudo-Renner-Teller couplings on them. The nonradiative decay of the 1 Σ u + electronic state is studied, and it is found that the decay rate is comparable with the prediction made for them to be qualified as a carrier of diffuse interstellar bands in the literature. The theoretical results are found to be in good accord with the available experimental results. [ABSTRACT FROM AUTHOR]