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Mark A. Payne, Angela P. Milce, Michael J. Frost, Brian J. Orr

Rovibrational Energy Transfer in the 4ν_CH Manifold of Acetylene, Viewed by IR-UV Double Resonance Spectroscopy. 3. State-to-State J-Resolved Kinetics

Time-resolved infrared-ultraviolet double resonance (IR-UV DR) spectroscopy is used to study the kinetics of collision-induced state-to-state molecular energy transfer between rovibrational states in the 12700-cm⁻¹ 4ν_CH manifold of the electronic ground state of acetylene (C₂H₂). Particular initial and final rovibrational J-states are prepared and monitored by a pair of tunable laser pulses (IR PUMP and UV PROBE) and the kinetic results recorded by continuously varying the time delay between those pulses at a set sample pressure. After allowing for collision-induced quenching of fluorescence and mass transfer from the IR-UV optical excitation zone (by beam flyout and diffusion), an array of kinetic data for J-resolved energy-transfer channels can be interpreted by means of a mechanistically structured master-equation model. This paper focuses on kinetics derived by probing C₂H₂ in its 4ν_CH J = 12 state (which is affected by intramolecular perturbations and implicated in unusual collision-induced quasi-continuous background effects) and J-resolved collision-induced rovibrational energy transfer with both even ΔJ and (supposedly forbidden) odd ΔJ.

Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0942-9352
Volume: 219, 05/2005
Pages: 601 - 633

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