An experimental and theoretical investigation of the C(1D) + D2 reaction

TL;DR

This study combines experimental measurements and ring polymer molecular dynamics simulations to investigate the C(1D) + D2 reaction at low temperatures, extending previous work on C(1D) + H2 and highlighting the importance of multiple potential energy surfaces.

Contribution

It extends prior research on C(1D) + H2 to include D2, demonstrating RPMD's effectiveness in modeling low-temperature reactions involving deuterated molecules.

Findings

RPMD results agree within 25% of experimental data

Both PESs contribute significantly to the reaction dynamics

The first excited PES becomes more influential at lower temperatures

Abstract

In a previous joint experimental and theoretical study of the barrierless chemical reaction C(1D) + H2 at low temperatures (300-50 K) [K. M. Hickson, J.-C. Loison, H. Guo, Y. V. Suleimanov, J. Phys. Chem. Lett., 2015, 6, 4194.], excellent agreement was found between experimental thermal rate constants and theoretical estimates based on ring polymer molecular dynamics (RPMD) over the two lowest singlet potential energy surfaces (PESs). Here, we extend this work to one of its deuterated counterparts, C(1D) + D2, over the same temperature range. Experimental and RPMD results are in very good agreement when contributions from both PESs to this chemical reaction are included in the RPMD simulations. The deviation between experiment and the RPMD calculations does not exceed 25 % and both results exhibit a slight negative temperature dependence. The first excited 1A" PES plays a more important role than the ground 1A' PES as the temperature is decreased, similar to our previous studies of the C(1D) + H2 reaction but with a more pronounced effect. The small differences in temperature dependence between the earlier and present experimental studies of C(1D) + H2/D2 reactions are discussed in terms of the use of non-equilibrium populations of ortho/para-H2/D2. We argue that RPMD provides a very convenient and reliable tool to study low-temperature chemical reactions.