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Unravelling the mechanisms of vibrational relaxation in solution

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Unravelling the mechanisms of vibrational relaxation in solution. / Grubb, Michael P; Coulter, Philip M; Marroux, Hugo J B; Orr-Ewing, Andrew J; Ashfold, Michael N R.

In: Chemical Science, Vol. 8, No. 4, 28.03.2017, p. 3062-3069.

Research output: Contribution to journalArticle

Harvard

Grubb, MP, Coulter, PM, Marroux, HJB, Orr-Ewing, AJ & Ashfold, MNR 2017, 'Unravelling the mechanisms of vibrational relaxation in solution', Chemical Science, vol. 8, no. 4, pp. 3062-3069. https://doi.org/10.1039/C6SC05234G

APA

Grubb, M. P., Coulter, P. M., Marroux, H. J. B., Orr-Ewing, A. J., & Ashfold, M. N. R. (2017). Unravelling the mechanisms of vibrational relaxation in solution. Chemical Science, 8(4), 3062-3069. https://doi.org/10.1039/C6SC05234G

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Author

Grubb, Michael P ; Coulter, Philip M ; Marroux, Hugo J B ; Orr-Ewing, Andrew J ; Ashfold, Michael N R. / Unravelling the mechanisms of vibrational relaxation in solution. In: Chemical Science. 2017 ; Vol. 8, No. 4. pp. 3062-3069.

Bibtex

@article{41332e4754214fcab85061b41f1247c2,
title = "Unravelling the mechanisms of vibrational relaxation in solution",
abstract = "We present a systematic study of the mode-specific vibrational relaxation of NO2 in six weakly-interacting solvents (perfluorohexane, perfluoromethylcyclohexane, perfluorodecalin, carbon tetrachloride, chloroform, and d-chloroform), chosen to elucidate the dominant energy transfer mechanisms in the solution phase. Broadband transient vibrational absorption spectroscopy has allowed us to extract quantum state-resolved relaxation dynamics of the two distinct NO2 fragments produced from the 340 nm photolysis of N2O4 → NO2(X) + NO2(A) and their separate paths to thermal equilibrium. Distinct relaxation pathways are observed for the NO2 bending and stretching modes, even at energies as high as 7000 cm-1 above the potential minimum. Vibrational energy transfer is governed by different interaction mechanisms in the various solvent environments, and proceeds with timescales ranging from 20-1100 ps. NO2 relaxation rates in the perfluorocarbon solvents are identical despite differences in acceptor mode state densities, infrared absorption cross sections, and local solvent structure. Vibrational energy is shown to be transferred to non-vibrational solvent degrees of freedom (V-T) through impulsive collisions with the perfluorocarbon molecules. Conversely, NO2 relaxation in chlorinated solvents is reliant on vibrational resonances (V-V) while V-T energy transfer is inefficient and thermal excitation of the surrounding solvent molecules inhibits faster vibrational relaxation through direct complexation. Intramolecular Vibrational Redistribution allows the symmetric stretch of NO2 to act as a gateway for antisymmetric stretch energy to exit the molecule. This study establishes an unprecedented level of detail for the cooling dynamics of a solvated small molecule, and provides a benchmark system for future theoretical work in solution.",
author = "Grubb, {Michael P} and Coulter, {Philip M} and Marroux, {Hugo J B} and Orr-Ewing, {Andrew J} and Ashfold, {Michael N R}",
year = "2017",
month = "3",
day = "28",
doi = "10.1039/C6SC05234G",
language = "English",
volume = "8",
pages = "3062--3069",
journal = "Chemical Science",
issn = "2041-6520",
publisher = "Royal Society of Chemistry",
number = "4",

}

RIS - suitable for import to EndNote

TY - JOUR

T1 - Unravelling the mechanisms of vibrational relaxation in solution

AU - Grubb, Michael P

AU - Coulter, Philip M

AU - Marroux, Hugo J B

AU - Orr-Ewing, Andrew J

AU - Ashfold, Michael N R

PY - 2017/3/28

Y1 - 2017/3/28

N2 - We present a systematic study of the mode-specific vibrational relaxation of NO2 in six weakly-interacting solvents (perfluorohexane, perfluoromethylcyclohexane, perfluorodecalin, carbon tetrachloride, chloroform, and d-chloroform), chosen to elucidate the dominant energy transfer mechanisms in the solution phase. Broadband transient vibrational absorption spectroscopy has allowed us to extract quantum state-resolved relaxation dynamics of the two distinct NO2 fragments produced from the 340 nm photolysis of N2O4 → NO2(X) + NO2(A) and their separate paths to thermal equilibrium. Distinct relaxation pathways are observed for the NO2 bending and stretching modes, even at energies as high as 7000 cm-1 above the potential minimum. Vibrational energy transfer is governed by different interaction mechanisms in the various solvent environments, and proceeds with timescales ranging from 20-1100 ps. NO2 relaxation rates in the perfluorocarbon solvents are identical despite differences in acceptor mode state densities, infrared absorption cross sections, and local solvent structure. Vibrational energy is shown to be transferred to non-vibrational solvent degrees of freedom (V-T) through impulsive collisions with the perfluorocarbon molecules. Conversely, NO2 relaxation in chlorinated solvents is reliant on vibrational resonances (V-V) while V-T energy transfer is inefficient and thermal excitation of the surrounding solvent molecules inhibits faster vibrational relaxation through direct complexation. Intramolecular Vibrational Redistribution allows the symmetric stretch of NO2 to act as a gateway for antisymmetric stretch energy to exit the molecule. This study establishes an unprecedented level of detail for the cooling dynamics of a solvated small molecule, and provides a benchmark system for future theoretical work in solution.

AB - We present a systematic study of the mode-specific vibrational relaxation of NO2 in six weakly-interacting solvents (perfluorohexane, perfluoromethylcyclohexane, perfluorodecalin, carbon tetrachloride, chloroform, and d-chloroform), chosen to elucidate the dominant energy transfer mechanisms in the solution phase. Broadband transient vibrational absorption spectroscopy has allowed us to extract quantum state-resolved relaxation dynamics of the two distinct NO2 fragments produced from the 340 nm photolysis of N2O4 → NO2(X) + NO2(A) and their separate paths to thermal equilibrium. Distinct relaxation pathways are observed for the NO2 bending and stretching modes, even at energies as high as 7000 cm-1 above the potential minimum. Vibrational energy transfer is governed by different interaction mechanisms in the various solvent environments, and proceeds with timescales ranging from 20-1100 ps. NO2 relaxation rates in the perfluorocarbon solvents are identical despite differences in acceptor mode state densities, infrared absorption cross sections, and local solvent structure. Vibrational energy is shown to be transferred to non-vibrational solvent degrees of freedom (V-T) through impulsive collisions with the perfluorocarbon molecules. Conversely, NO2 relaxation in chlorinated solvents is reliant on vibrational resonances (V-V) while V-T energy transfer is inefficient and thermal excitation of the surrounding solvent molecules inhibits faster vibrational relaxation through direct complexation. Intramolecular Vibrational Redistribution allows the symmetric stretch of NO2 to act as a gateway for antisymmetric stretch energy to exit the molecule. This study establishes an unprecedented level of detail for the cooling dynamics of a solvated small molecule, and provides a benchmark system for future theoretical work in solution.

U2 - 10.1039/C6SC05234G

DO - 10.1039/C6SC05234G

M3 - Article

VL - 8

SP - 3062

EP - 3069

JO - Chemical Science

JF - Chemical Science

SN - 2041-6520

IS - 4

ER -