Quantum and Semiclassical Dynamics of Nonadiabatic Electronic Excitation of C(³P) to C¹D) by Hyperthermal Collisions with N₂

Abstract

The dynamics and kinetics of nonadiabatic excitation of C( 3 P) to C( 1 D) induced by hyperthermal collisions with N 2 molecules are investigated using a quantum mechanical and two semiclassical nonadiabatic methods. The full-dimensional interaction potential energy surfaces and spin−orbit coupling, which facilitates the spin-forbidden process, are represented by a recently constructed diabatic potential energy matrix. The multistate quantum dynamics for selected partial waves found small transition probabilities due to the weak spin−orbit coupling. The spin-flip transition is the most favored near the threshold due to effective curve crossing. Strong oscillations are also found in the probabilities, which are attributable to resonances supported by the deep well in the singlet-state potential. Vibrational state-specified rate coefficients are reported from J-shifted quantum dynamics calculations, and they follow the Arrhenius form. Vibrational excitation in the N 2 collision partner is found to increase the excitation rate at low temperatures, but the trend is reversed at high temperatures. The two semiclassical methods qualitatively reproduce the quantum rate coefficients.

Quantum and semiclassical studies of nonadiabatic electronic transitions between N(4S) and N(2D) by collisions with N2

“…The solid lines in these panels represent the crossing seam, near which non-adiabatic transitions between the doublet and quartet states take place, facilitated by the spin–orbit coupling. Similar with the C + N 2 system, 46 the crossing seam is mostly parallel to the N–N internuclear distance ( r ) and perpendicular to the scattering coordinate ( R ), which suggests that the vibrational excitation in the initial N 2 should have a relatively minor impact and the translational energy along the scattering coordinate might have a significant effect.…”

“…The small rate coefficients for these two spin-forbidden processes have also been seen in our recent investigation of the excitation of C( 3 P) to C( 1 D) by collisions with N 2 . 46 There is no experimental data to compare with, as no such measurements have so far been reported.…”

“…40 Many improvements over the FSSH method have been proposed, [41][42][43] but we will in this work use the Coherent Switching with Decay of Mixing (CSDM), 44 which has been tested in many systems, 45 including our recent study of the spin-forbidden excitation of C( 3 P) to C( 1 D) by collisions with N 2 . 46 These semiclassical methods are numerically inexpensive and thus can be used for larger systems. However, it is essential to valid such a semi-classical approach against exact quantum mechanical calculations.…”

Generalized Semiclassical Ehrenfest Method: A Route to Wave Function-Free Photochemistry and Nonadiabatic Dynamics with Only Potential Energies and Gradients

“…It is shown elsewhere that CSDM agrees well with accurate quantum dynamics for realistic full-dimensional electronically inelastic collisions when the CSDM and accurate dynamics calculations are carried out with the same coupled potential surfaces. ,,,− …”

State-to-State Quantum Dynamics Study of Intramolecular Isotope Effects on Be(1S) + HD (v0 = 2, j0 = 0) → BeH/BeD + H/D Reaction

“…The most reliable strategy for studying reaction dynamics theoretically is to perform quantum mechanics calculations on a high-quality PES [ 38 , 39 , 40 ]. The quantum TDWP method [ 41 , 42 , 43 , 44 , 45 ] can not only accurately calculate dynamics data but also has a relatively small numerical cost, meaning that it has been widely applied to simple reaction systems [ 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ]. A detailed description of the TDWP method has been presented in the relevant literature, and we only give the essentials and main equations.…”