Different Dynamics of CH3 and Cl Fragments from Photodissociation of CH3Cl in Clusters

0532538 - ÚFCH JH 2021 RIV US eng J - Článek v odborném periodiku
Vinklárek, Ivo S. - Rakovský, Jozef - Poterya, Viktoriya - Fárník, Michal
Different Dynamics of CH3 and Cl Fragments from Photodissociation of CH3Cl in Clusters.
Journal of Physical Chemistry A. Roč. 124, č. 38 (2020), s. 7633-7643. ISSN 1089-5639. E-ISSN 1520-5215
Grant CEP: GA ČR(CZ) GA19-14105S
Institucionální podpora: RVO:61388955
Klíčová slova: potential-energy surfaces * spectroscopy * atoms
Obor OECD: Physical chemistry
Impakt faktor: 2.781, rok: 2020
Způsob publikování: Omezený přístup

We investigate the photodissociation of CH3Cl at 193.3 nm using the velocity map imaging technique in (CH3Cl)n clusters in comparison with isolated molecules. Our results for the isolated molecules are in excellent agreement with the previous study of Cl fragments, and we extend it by detecting also the CH3(ν = 0) fragments. For the clusters, the Cl (and Cl*) and CH3 fragment images are dominated by intense central isotropic features. The corresponding kinetic energy distributions (KEDs) reveal significant differences in the CH3 and Cl fragment dynamics. While the CH3 fragments exhibit a very narrow near-zero kinetic energy peak, pointing to almost complete caging of CH3 fragments, the Cl (and Cl*) fragments show more structured KEDs extending all the way to the maximum available kinetic energy. The Cl KED spectra have a bimodal character with two broad peaks close to zero and around 0.6 eV. We observe a higher ICH3(ν=0)/ICl signal ratio from the clusters compared to the monomers. This is attributed to an efficient quenching of the higher vibrationally excited ν2 states of the CH3 fragments generated in the photodissociation. Collisional quenching of these excited states in clusters enhances the detected CH3(ν = 0) state. Finally, we determine the [Cl*]/[Cl] branching ratio for the photodissociation pathways in the clusters as ≈0.55 ± 0.15 compared to 0.86 for the isolated molecules, which is also attributed to the collisional quenching of the excited state in the clusters. The clusters and photofragment dynamics are discussed.
Trvalý link: http://hdl.handle.net/11104/0310999