Fuchs, Stefan and Dick, Bernhard (2024) Photodissociation of deuterated pyrrole-ammonia clusters: H-atom transfer or electron coupled proton transfer? PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 26 (20). ISSN 1463-9076, 1463-9084
Full text not available from this repository. (Request a copy)Abstract
Several years ago the discovery of a conical intersection offered an explanation for the ultafast photodissociation of pyrrole. Subsequently, the photodissociation of pyrrole ammonia complexes PyH*(NH3)n with n >= 3 was studied in the gas phase as a model for a hydrogen-bond forming solvent. Two alternative mechanisms, electron coupled proton transfer (ECPT) and hydrogen atom transfer (HAT, also called the impulsive model, IM), have been proposed. The parent 1 : 1 complex was never studied, due to the short lifetime of the NH4 radical fragment. Here we report experiments on the deuterated species PyD*(ND3)n, including the 1 : 1 complex (n = 1). The velocity distribution of the ND4 radical is well approximated by a Maxwell-Boltzmann distribution of T approximate to 530 K, with a negative anisotropy parameter of beta = -0.3. The impulsive model predicts a much narrower velocity distribution with larger negative anisotropy. The ECPT model predicts a long lived intermediate that should allow thermal equilibration of the vibrational energy but should also destroy the rotational memory of the initially excited state. The average kinetic energy agrees with the prediction of the impulsive model, whereas the wide range of kinetic energies is more in line with ECPT. Hence the mechanism seems to be more complex and requires further theoretical modelling. What is the mechanism of photodissociation of the PyH-NH3 complex into the radicals Py and NH4 - impulsive hydrogen transfer, electron coupled proton transfer, or fragmentation after thermalization in the excited state? A molecular beam study.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | HYPERVALENT MOLECULAR CLUSTERS; EXCITED-STATE DYNAMICS; HYDROGEN-TRANSFER; RYDBERG STATES; PHOTOIONIZATION; DISSOCIATION; ELIMINATION; GENERATION; DETACHMENT; EXCITATION; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry III - Physical Chemistry (Molecular Spectroscopy and Photochemistry) Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry III - Physical Chemistry (Molecular Spectroscopy and Photochemistry) > Prof. Dr. Bernhard Dick |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 28 Jul 2025 11:30 |
| Last Modified: | 28 Jul 2025 11:30 |
| URI: | https://pred.uni-regensburg.de/id/eprint/63861 |
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