Nonadiabatic couplings and charge transfer study in H + CS+collision using time-dependent quantum dynamics

A new global analytical ab initio potential energy surface for the dynamics of the C+(2P) + SH(X2Π) reaction

The global potential energy surface (PES) of HCS⁺(X¹Σ⁺) is constructed using many-body expansion (MBE) methodology. The obtained analytical function is found by fitting the 7907 ab initio energy points computed at the Davidson-corrected multi-reference configuration interaction level with the aug-cc-pV(5+d)Z basis set. The final root mean square error is 0.0419 eV, and the maximum deviation is 0.2039 eV, showing that the analytical formula agrees well with the energy points. The topological features are calculated and discussed based upon the analytical PES of HCS⁺(X¹Σ⁺). The reaction probability, integral cross sections and other details of the C⁺(²P) + SH(X²Π) → H(²S) + CS⁺(X²Σ⁺) reaction are investigated using the quasi-classical trajectory and time-dependent quantum wave packet methods.

Quantum Scattering Calculations for Rotational Excitations of by Hydrogen Atom: Potential Energy Surfaces and Rate Coefficients

Ab initio calculations are performed to determine new potential energy surfaces for the ground state and low-lying excited states of C₃ induced by collision with atomic hydrogen. The calculations are performed using the multireference configuration interaction method including Davidson's correction using aug-cc-pVQZ (augmented correlation consistent polarized valence quadruple zeta) basis sets. Nonadiabatic effects leading to avoided crossings are observed between ground and excited states. The computed points of the ground-state surface are fitted to an analytical form suitable for time-independent quantum scattering calculations of the state-to-state collisional cross sections. The close-coupling calculations are performed up to 1000 cm^-1. Resonances are observed at very low energies. Among all the rotational transitions, Δj = 2 is found to be predominant for excitation. After Boltzmann thermal averaging collisional cross sections, rate coefficients for rotational levels j = 0, 2, ..., 8 are obtained and discussed covering the temperature up to 100 K. The magnitude of the state-to-state excitation rate obtained is maximum for j = 0 → 2 transition and decrease for other higher excitations. The results computed in this work will be crucially required to accurately model the abundance of carbon trimer and its hydrocarbon form in space.

Ab Initio Potential Energy Surfaces of C3 Collision with Proton and Quantum Dynamics of Rotational Transition

New ab initio potential energy surfaces have been generated for the ground state and low-lying excited states of the H⁺ + C₃ system using the multireference configuration interaction (MRCI) method with Dunning's augmented correlation consistent polarized valence quadruple-zeta (aug-cc-pVQZ) basis sets. The ground state and low-lying excited states show avoided crossing, indicating nonadiabatic coupling. The anisotropy of the ground-state surface has been analyzed by computing the multipolar expansion coefficients with the frozen C-C equilibrium bond length. The asymptotic potential has been merged with the interaction potential by spline fit. This potential is then used in the full close coupling calculations of rotational excitation in C₃ collision with the proton for rotational levels j = 0, 2, 4, 6, 8 at very low collision energy. By averaging the cross sections over a Boltzmann distribution of velocities of the incoming atom, we obtain and discuss corresponding rate coefficients of C₃ collision with the proton in the interstellar medium.