Molecular-dynamics simulation of collisional energy transfer from vibrationally highly excited azulene in compressed CO2

Heidelbach, C.; Fedchenia, I. I.; Schwarzer, Dirk; Schroeder, J.

doi:10.1063/1.476474

Cited by 37 publications

(40 citation statements)

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“…The theoretical background of classical MD calculations is provided elsewhere. [96,123,124] Direct non-equilibrium MD simulations have been found to reproduce important features of the energy gain and loss of FC-active CI 2 stretch modes observed in the experiments. A key finding of the studies of Kaeb et al is that most of the excess energy deposited by the IR pump is dissipated into the solvent through the lowest-frequency CÀH mode (CH 2 rocking vibration), while the lowest-frequency mode (CI 2 bending) is merely a spectator in the overall process of energy redistribution and relaxation and is not significantly populated at all on the timescale of the relaxation.…”

Section: Methodsmentioning

confidence: 73%

“…As a result of this balance, VET is mostly determined by x(w) at frequencies w >~100 cm À1 , that is, the range beyond the lowest-frequency modes describing complex collective motions of the liquid. [69,123,124] x(w) is defined in Equation (7) (C(t) is proportional to the force autocorrelation function).…”

Section: Methodsmentioning

confidence: 99%

“…[46,112] Beyond such an approach, flexible MD calculations should be able to treat IVR and VET in solution, even for polyatomic systems. Recently, VET of azulene in solution and supercritical fluids [122][123][124] and VET as well as IVR of diiodomethane in solution was investigated in full MD simulations. [96] The latter study has accompanied our recent experimental investigations of the intra-and intermolecular vibrational energy flow of CH 2 I 2 in solution.…”

Section: Methodsmentioning

confidence: 99%

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

2003

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Energized molecules are the essential actors in chemical transformations in solution. As the rearrangement of bonds requires a movement of nuclei, vibrational energy is often the driving force for a reaction. Vibrational energy can be redistributed within the "hot" molecule, or relaxation can occur when molecules interact. Both processes govern the rates, pathways, and quantum yields of chemical transformations in solution. Unfortunately, energy transfer and the breaking, formation, and rearrangement of bonds take place on ultrafast timescales. This Review highlights experimental approaches for the direct, ultrafast measurement of photoinduced femtochemistry and energy flow in solution. In the first part of this Review, we summarize recent experiments on intra- and intermolecular energy transfer. The second part discusses photoinduced decomposition of large organic peroxides, which are used as initiators in free radical polymerization. The mechanisms and timescales of their decarboxylation determine the initial steps of polymerization and the microstructure of the polymer product.

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Section: Methodsmentioning

confidence: 73%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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

2003

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“…The second general observation is that while measurements and calculations of relaxation rates are directly proportional to pressure at pressures low enough for isolated gasmolecule collisions, the measurements of Schwarzer et al 14 and the calculations of Heidelbach et al 20,21 and Paul et al 23 show that at high enough pressures, the relaxation rate grows more slowly than in direct proportion to the pressure. The Schwarzer et al measurements of the relaxation of azulene in a variety of supercritical fluids including CO 2 show that a change in relaxation rate growth from direct proportional dependence to slower growth occurs at a density of ∼1 mol/L or ∼25 atm (estimated using the ideal gas law).…”

Section: Introductionmentioning

confidence: 93%

“…Because of the expense, such simulations are unusual, especially for highly excited molecules of greatest interest in combustion for which the time required for thermalization can be quite long. Several examples can be found in the work of Heidelbach et al 20 for azulene/CO 2 and of Paul et al 23 for the C 6 F 6 /N 2 system.…”

Section: Introductionmentioning

confidence: 96%

Pressure effects on the relaxation of an excited nitromethane molecule in an argon bath

Rivera‐Rivera

Wagner

Sewell

et al. 2015

The Journal of Chemical Physics

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Classical molecular dynamics simulations were performed to study the relaxation of nitromethane in an Ar bath (of 1000 atoms) at 300 K and pressures 10, 50, 75, 100, 125, 150, 300, and 400 atm. The molecule was instantaneously excited by statistically distributing 50 kcal/mol among the internal degrees of freedom. At each pressure, 1000 trajectories were integrated for 1000 ps, except for 10 atm, for which the integration time was 5000 ps. The computed ensemble-averaged rotational energy decay is ∼100 times faster than the vibrational energy decay. Both rotational and vibrational decay curves can be satisfactorily fit with the Lendvay-Schatz function, which involves two parameters: one for the initial rate and one for the curvature of the decay curve. The decay curves for all pressures exhibit positive curvature implying the rate slows as the molecule loses energy. The initial rotational relaxation rate is directly proportional to density over the interval of simulated densities, but the initial vibrational relaxation rate decreases with increasing density relative to the extrapolation of the limiting low-pressure proportionality to density. The initial vibrational relaxation rate and curvature are fit as functions of density. For the initial vibrational relaxation rate, the functional form of the fit arises from a combinatorial model for the frequency of nitromethane "simultaneously" colliding with multiple Ar atoms. Roll-off of the initial rate from its low-density extrapolation occurs because the cross section for collision events with L Ar atoms increases with L more slowly than L times the cross section for collision events with one Ar atom. The resulting density-dependent functions of the initial rate and curvature represent, reasonably well, all the vibrational decay curves except at the lowest density for which the functions overestimate the rate of decay. The decay over all gas phase densities is predicted by extrapolating the fits to condensed-phase densities.

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Echtzeit‐Beobachtung photoinduzierter Chemie und molekularen Energietransfers in Lösung

2003

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Hochangeregte Moleküle sind die wichtigen Akteure bei chemischen Transformationen in Lösung. Da die Reorganisation von Bindungen eine Kernbewegung voraussetzt, ist es oft die Schwingungsenergie, die Reaktionen maßgeblich vorantreibt. Schwingungsenergie kann innerhalb des “heißen” Moleküls umverteilt oder in Stößen mit anderen Molekülen abgegeben werden. Beide Prozesse beeinflussen die Mechanismen, Geschwindigkeiten und Ausbeuten chemischer Transformationen. Die Zeitskalen, auf denen Energie relaxiert und Bindungen gebrochen, geformt oder umgelagert werden, liegen jenseits unserer Erfahrung und Vorstellungskraft. Dieser Aufsatz beschreibt leistungsstarke experimentelle Ansätze für die direkte Messung des molekularen Energieflusses und photoinduzierter Chemie auf ultrakurzer Zeitskala in Lösung. Im ersten Teil des Aufsatzes werden Experimente zur direkten Messung der intra‐ und intermolekularen Energierelaxation diskutiert, der Fokus des zweiten Teils liegt auf dem ultraschnellen photoinduzierten Zerfall organischer Peroxide, die als Initiatoren in radikalischen Polymerisationen zum Einsatz kommen. Die Mechanismen und Zeitskalen ihrer Decarboxylierung sind wichtig für die primären Schritte einer radikalischen Polymerisation und die Mikrostruktur des Polymerproduktes.

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Molecular-dynamics simulation of collisional energy transfer from vibrationally highly excited azulene in compressed CO2

Abstract: Articles you may be interested inHigh resolution IR diode laser study of collisional energy transfer between highly vibrationally excited monofluorobenzene and CO2: The effect of donor fluorination on strong collision energy transfer

Cited by 37 publications

References 50 publications

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

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

Pressure effects on the relaxation of an excited nitromethane molecule in an argon bath

Echtzeit‐Beobachtung photoinduzierter Chemie und molekularen Energietransfers in Lösung

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