Two-Dimensional Infrared Spectroscopy From the Gas to Liquid Phase: Density Dependent J-Scrambling, Vibrational Relaxation, and the Onset of Liquid Character

2019 ◽  
Author(s):  
Greg Ng Pack ◽  
Matthew Rotondaro ◽  
Parth Shah ◽  
Aritra Mandal ◽  
Shyamsunder Erramilli ◽  
...  
Keyword(s):  
Vibrational Energy ◽  
Rotational Relaxation ◽  
Vibrational Energy Relaxation ◽  
Pump Probe ◽  
Solution Dynamics ◽  
Supercritical Phase ◽  
Supercritical Solution ◽  
Asymmetric Stretch ◽  
Two Dimensional Infrared Spectroscopy ◽  
Vibrational Equilibrium

Ultrafast 2DIR spectra and pump-probe responses of the N2O n 3 asymmetric stretch in SF6 as a function of density from the gas to supercritical phase and liquid are reported. 2DIR spectra unequivocally reveal free rotor character at all densities studied in the gas and supercritical region. Analysis of the 2DIR spectra determines that J-scrambling or rotational relaxation in N2O is highly efficient, occurring in ~1.5 to ~2 collisions with SF6 at all non-liquid densities. In contrast, N2O n 3 vibrational energy relaxation requires ~15 collisions, and complete vibrational equilibrium occurs on the ~ns scale at all densities. An independent binary collision model is sufficient to describe these supercritical state point dynamics. The N2O n 3 in liquid SF6 2DIR spectrum shows no evidence of free rotor character or spectral diffusion. Using these 2DIR results, hindered rotor or liquid-like character is found in gas and all supercritical solutions for SF6 densities ³ r * = 0.3, and increases with SF6 density. 2DIR spectral analysis offers direct time domain evidence of critical slowing for SF6 solutions closest to the critical point density. Applications of 2DIR to other high density and supercritical solution dynamics and descriptions are discussed. <br>

Two-Dimensional Infrared Spectroscopy From the Gas to Liquid Phase: Density Dependent J-Scrambling, Vibrational Relaxation, and the Onset of Liquid Character

2019 ◽  
Author(s):  
Greg Ng Pack ◽  
Matthew Rotondaro ◽  
Parth Shah ◽  
Aritra Mandal ◽  
Shyamsunder Erramilli ◽  
...  
Keyword(s):  
Vibrational Energy ◽  
Rotational Relaxation ◽  
Vibrational Energy Relaxation ◽  
Pump Probe ◽  
Solution Dynamics ◽  
Supercritical Phase ◽  
Supercritical Solution ◽  
Asymmetric Stretch ◽  
Two Dimensional Infrared Spectroscopy ◽  
Vibrational Equilibrium

Ultrafast 2DIR spectra and pump-probe responses of the N2O n 3 asymmetric stretch in SF6 as a function of density from the gas to supercritical phase and liquid are reported. 2DIR spectra unequivocally reveal free rotor character at all densities studied in the gas and supercritical region. Analysis of the 2DIR spectra determines that J-scrambling or rotational relaxation in N2O is highly efficient, occurring in ~1.5 to ~2 collisions with SF6 at all non-liquid densities. In contrast, N2O n 3 vibrational energy relaxation requires ~15 collisions, and complete vibrational equilibrium occurs on the ~ns scale at all densities. An independent binary collision model is sufficient to describe these supercritical state point dynamics. The N2O n 3 in liquid SF6 2DIR spectrum shows no evidence of free rotor character or spectral diffusion. Using these 2DIR results, hindered rotor or liquid-like character is found in gas and all supercritical solutions for SF6 densities ³ r * = 0.3, and increases with SF6 density. 2DIR spectral analysis offers direct time domain evidence of critical slowing for SF6 solutions closest to the critical point density. Applications of 2DIR to other high density and supercritical solution dynamics and descriptions are discussed. <br>

The influence of rotational and vibrational energy relaxation on boundary-layer stability

1998 ◽  
Vol 372 ◽  
pp. 93-118 ◽  
Author(s):  
FABIO P. BERTOLOTTI
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Bulk Viscosity ◽  
Vibrational Energy ◽  
Energy Relaxation ◽  
Rapid Expansion ◽  
Rotational Relaxation ◽  
Stagnation Temperature ◽  
Relaxation Rates ◽  
Vibrational Energy Relaxation

We investigate the influence of rotational and vibrational energy relaxation on the stability of laminar boundary layers in supersonic flows by numerically solving the linearized equations of motion for a flow in thermal non-equilibrium. We model air as a mixture of nitrogen, oxygen and carbon dioxide, and derive accurate models for the relaxation rates from published experimental data in the field of physical chemistry. The influence of rotational relaxation is to dampen high-frequency instabilities, consistent with the well known damping effect of rotational relaxation on acoustical waves. The influence of rotational relaxation can be modelled with acceptable accuracy through the use of the bulk-viscosity approximation when the bulk viscosity is computed with a formula described herein. Vibrational relaxation affects the growth of disturbances by changing the characteristics of the laminar mean flow. The influence is strongest when the flow field contains a region at, or near, stagnation conditions, followed by a rapid expansion, such as inside wind tunnels and around bodies with a blunt leading edge, whereby the rapid expansion causes the internal energy to freeze in a distribution out of equilibrium. For flows at Mach 4.5 and stagnation temperature of 1000 K, the total amplification exhibited by boundary-layer disturbances over a sharp flat plate in wind-tunnel flows can reach a value that is fifty times as high as the value computed under the assumption of thermal equilibrium. The difference in amplification can be twice as high in the case of a blunt flat plate at atmospheric flight conditions.

scholarly journals Viscosity Dependence of the Ultrafast Vibrational Dynamics of Borohydride in NaOH Solutions: Crowding Effect on Dihydrogen Bonds

2019 ◽  
Author(s):  
Clinton Johnson ◽  
Kai C. Gronborg ◽  
Thomas Brinzer ◽  
Zhe Ren ◽  
Sean Garrett-Roe
Keyword(s):  
Ground State ◽  
Vibrational Energy ◽  
Vibrational Energy Relaxation ◽  
Energy Redistribution ◽  
Vibrational Dynamics ◽  
Structure And Dynamics ◽  
2D Ir ◽  
Intramolecular Vibrational Energy Redistribution ◽  
Two Dimensional Infrared Spectroscopy ◽  
Viscosity Dependence

<p>Two-dimensional infrared spectroscopy (2D-IR) probes the local solvent structure and dynamics of the nu<sub>3</sub> mode (BH antisymmetric stretch) of borohydride (BH<sub>4</sub><sup>-</sup> ) in aqueous solution. The 2D-IR spectra of the BH stretches have broad and overlapping bands. Vibrational energy relaxation occurs on a 2 ps timescale. Energy that is initially deposited in BH stretching modes and directly in the solvent generates a long lived hot ground state. Before the hot ground state appears, some indications of intramolecular vibrational energy redistribution are observed. The solvent viscosity was varied (1.5–6 cP) by increasing the hydroxide concentration (0.1–7 M). Within the vibrational lifetime of the BH stretching modes, the rate of structural relaxation slows proportionally to the viscosity due to the overlap of the ions’s solvation shells.</p>

Asymmetric stretch vibrational energy relaxation of OClO in liquid water

2001 ◽  
Vol 343 (5-6) ◽  
pp. 581-587 ◽  
Author(s):  
Jens Poulsen ◽  
Thomas M. Nymand ◽  
Søren R. Keiding
Keyword(s):  
Liquid Water ◽  
Vibrational Energy ◽  
Energy Relaxation ◽  
Vibrational Energy Relaxation ◽  
Asymmetric Stretch

Intermolecular vibrational energy transfer enabled by microcavity strong light–matter coupling

Science ◽  
2020 ◽  
Vol 368 (6491) ◽  
pp. 665-667 ◽  
Author(s):  
Bo Xiang ◽  
Raphael F. Ribeiro ◽  
Matthew Du ◽  
Liying Chen ◽  
Zimo Yang ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Vibrational Energy ◽  
Intermolecular Forces ◽  
Vibrational Energy Transfer ◽  
Strong Light ◽  
Pump Probe ◽  
Donor And Acceptor ◽  
Weak Intermolecular Forces ◽  
Two Dimensional Infrared Spectroscopy ◽  
Energy Transfer Pathway

Selective vibrational energy transfer between molecules in the liquid phase, a difficult process hampered by weak intermolecular forces, is achieved through polaritons formed by strong coupling between cavity photon modes and donor and acceptor molecules. Using pump-probe and two-dimensional infrared spectroscopy, we found that the excitation of the upper polariton, which is composed mostly of donors, can efficiently relax to the acceptors within ~5 picoseconds. The energy-transfer efficiency can be further enhanced by increasing the cavity lifetime, suggesting that the energy transfer is a polaritonic process. This vibrational energy-transfer pathway opens doors for applications in remote chemistry, sensing mechanisms, and vibrational polariton condensation.

scholarly journals Slow Relaxation Processes in SF6 Gas After Pumping by a CO2 Laser Pulse

1991 ◽  
Vol 11 (1) ◽  
pp. 39-48
Author(s):  
Iwao Kitazima ◽  
Hiroshi Iwasawa
Keyword(s):  
Molecular Diffusion ◽  
Vibrational Energy ◽  
Pump Intensity ◽  
Energy Relaxation ◽  
Probe Method ◽  
Relaxation Processes ◽  
Gas Cell ◽  
Vibrational Energy Relaxation ◽  
Pump Probe ◽  
Gas Cooling

The vibrational energy relaxation and distribution in SF6 at the collisional condition of 2 Torr was measured with the pump-probe method by use of two tunable CO2 300 ns-pulse lasers at the delay time up to 400 μs. The 10.6 μs P(30) pump intensity was 0.4 J/cm2. The probed spectra, divided into two parts, the induced transmission at the P(10)–P(22) and the absorption at the P(24)–P(32), were red-shifted by 50 μs and then slowly back to the initial. The time variation of induced signals was divided into the four regions due to the following processes; (I) the formation of nonthermal distribution in the ν3 mode and quasi-continuum with 1 μs, (II) the broad redistribution by the rise-up of vibrational temperature in 50 μs-duration, (III) the molecular diffusion or expansion out of the pumped region locally heated up by the V–T relaxation in another 60 μs, (IV) the gas cooling corresponding to the energy relaxation or population depletion over 400 μs. So, this pump-probe method at the collisional conditions will easily give us some informations, with a short gas cell and a suitable time scale, on those slow processes.

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