Picosecond Vibrational Spectroscopy of Intermolecular Energy Transfer and Overtone Relaxation in Liquid Bromoform

Abstract

Intermolecular energy transfer in liquid bromoform and d-bromoform was investigated by help of picosecond IR and Raman spectroscopy. Fora comprehensive interpretation of the corresponding results the study of C-H bending overtone (2V4) relaxation was necessary; the effective vibrational lifetime of this vibrational mode was determined to T1 = 3±1 ps. For the intermolecular transfer a dominating process between the intramolecularly equilibrated C-Br stretching modes V2 and vs of CHBr3 and CDBr3 with a rate constant of 4.10 10 S-l was recognized. Other possible channels, particularly the one between the quasi resonant modes VI (C-D) and 2v4(C-H) were found to be negligible.The question if the intermolecular energy transfer is mainly caused by molecular collisions or if other processes like dipole-dipole interaction play an important role will be an interesting aspect of future work in this field.

Watching Photoinduced Chemistry and Molecular Energy Flow in Solution in Real Time

“…Of particular importance are experiments in which the vibrational energy is initially deposited with some degrees of freedom in the molecule, and is then dissipated into lower-energy vibrations and into the solvent. [20-23, 25, 26, 28-36, 61-70] Several time-resolved techniques such as IR absorption spectroscopy, [20,24,62,[71][72][73] antiStokes Raman spectroscopy, [28-30, 35, 65, 74-77] and UV absorption spectroscopy [25-27, 56, 61] have been successfully applied to measure rates of IVR and VET of organic molecules. IVR and VET in halogenated hydrocarbons, [20,21,24,27,34,62,63,78] benzene, [65] nitromethane, [30] acetonitrile, [28] alcohols, [35,36,66,67] and water [78,79] have been studied in considerable detail in the time domain employing different techniques of (state-selective) pump-and-probe spectroscopy.…”

Vibrational energy relaxation of polyatomic molecules in liquids: The solvent’s perspective

“…Most importantly, there is the possibility of solvent-assisted intramolecular vibrational relaxation ͑solvent-assisted IVR͒, in which vibrational energy flows between different solute modes, with the main responsibility of the solvent the removal ͑or addition͒ of enough energy to make the process conserve energy. There is also the opportunity for solvent-assisted intermolecular energy transfer, 19 with most of the transfer taking place between intramolecular modes on different molecules and the intermolecular degrees of freedom taking up the remainder. So what determines the sequence of energy-transfer events in dissolved polyatomics and how much of a role does the solvent play?…”

Vibrational relaxation of the CH stretch fundamental in liquid CHBr3

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] This leads to the identification of primary acceptor modes and the most likely pathways for the decay of the excitation. The objective of such studies, both theoretical and experimental, is to understand how the absorbed energy is channeled into various intra-and intermolecular modes.…”