Photodissociation dynamics of CO-forming channel of methyl formate at 193 nm: a computational study

Abstract

The dissociation dynamics of CO-forming channel on the ground state (S₀) of methyl formate has been studied by direct dynamics simulations and Generalised Multi-Centre Impulsive Model (GMCIM) under photon energy of 193 nm. Comparison of the simulated product-state distribution with experimental results permits us to conclude that the major forming channel of primary CO is through the conventional three-centre saddle point (TS1), which leads to CO (X¹∑⁺) + CH₃OH (${\tilde{\mathrm{X}}}^1{\text{A}}^{\mathrm{\prime }}$) products. Besides, the photolysis wavelength dependence of product state distribution via TS1 is successfully interpreted by GMCIM, whereas the excess energy above the barrier top is treated by sudden approximation. In addition, the possibility to produce secondary CO is also considered. With the aid of phase-space theory simulation, it turns out that the most probable route to form secondary CO is via the sequential triple fragmentation due to the further decomposition of energetic HCO(${\tilde{\mathrm{X}}}^2{\text{A}}^{\mathrm{\prime }}$), which takes place on the S₀ surface of methyl formate.

GRAPHICAL ABSTRACT

KEYWORDS:

• Direct dynamics simulations
• Generalised Multi-Center Impulsive Model
• sudden approximation

Acknowledgements

The authors are pleased to dedicate this article to the Special Issue of Molecular Physics in honour of Oleg Vasyutinskii. FP gratefully acknowledges the Italian Ministry for Education, University and Research, MIUR, for financial support through SIR 2014 ‘Scientific Independence of young Researchers’ (RBSI14U3VF). PYT gratefully acknowledges the Ministry of Science and Technology (MOST) of Taiwan, Republic of China (MOST 110-2113-M-005-020).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Ministero dell'Istruzione, dell'Università e della Ricerca  [grant number RBSI14U3VF].