Evolution of the homogeneous IR spectrum of a highly vibrationally excited molecule as a result of a change in its vibrational energy

1988 ◽  
Vol 47 (3) ◽  
pp. 229-232 ◽  
Author(s):  
S. I. Ionov ◽  
A. A. Stuchebryukhov ◽  
V. N. Bagratashvili ◽  
V. N. Lokhman ◽  
G. N. Makarov ◽  
...  
Keyword(s):  
Ir Spectrum ◽  
Vibrational Energy ◽  
Excited Molecule ◽  
Vibrationally Excited

MULTISTAGE DEACTIVATION IN THE PHOTOLYSIS OF HEXAFLUOROACETONE

1964 ◽  
Vol 42 (6) ◽  
pp. 1345-1354 ◽  
Author(s):  
A. N. Strachan ◽  
R. K. Boyd ◽  
K. O. Kutschke
Keyword(s):  
Vibrational Energy ◽  
Excited Molecule ◽  
Single Step ◽  
Inert Gases ◽  
Ultraviolet Region ◽  
Vibrationally Excited ◽  
Vibrational Levels ◽  
New Treatments ◽  
Lower Group ◽  
Vibrational Equilibrium

In principle the vibrationally excited molecule in an upper electronic state, formed by absorption in the ultraviolet region of the spectrum, can attain vibrational equilibrium by two mechanisms. In most discussions of this degradation of vibrational energy it has been considered that the data are represented adequately by a single-step deactivation from high to low vibrational levels rather than by a multistep cascade from one group of vibrational levels to the next lower group. The present work suggests new treatments of the experimental data by which it is possible to distinguish between the single- and the multi-step deactivation processes. It is demonstrated that the literature data on the quantum yield for the decomposition of hexafluoroacetone is better interpreted in terms of a multistep deactivation. Some new data are presented which support this conclusion.Methods to evaluate the efficiencies as deactivating agents of added inert gases are discussed. It is suggested that the deactivation of excited hexafluoroacetone by hydrocarbons might involve chemical rather than, or in addition to, purely physical quenching.

scholarly journals The calculation of TV, VT, VV, VV' − rate coefficients for the collisions of the main atmospheric components

1998 ◽  
Vol 16 (7) ◽  
pp. 838-846 ◽  
Author(s):  
A. S. Kirillov
Keyword(s):  
Experimental Data ◽  
Energy Transfer ◽  
Vibrational Energy ◽  
Relaxation Times ◽  
Atmospheric Composition ◽  
Rate Coefficients ◽  
Frequency Change ◽  
Vibrational Energy Transfer ◽  
Ion Chemistry ◽  
Vibrationally Excited

Abstract. The first-order perturbation approximation is applied to calculate the rate coefficients of vibrational energy transfer in collisions involving vibrationally excited molecules in the absence of non-adiabatic transitions. The factors of molecular attraction, oscillator frequency change, anharmonicity, 3-dimensionality and quasiclassical motion have been taken into account in the approximation. The analytical expressions presented have been normalized on experimental data of VT-relaxation times in N2 and O2 to obtain the steric factors and the extent of repulsive exchange potentials in collisions N2-N2 and O2-O2. The approach was applied to calculate the rate coefficients of vibrational-vibrational energy transfer in the collisions N2-N2, O2-O2 and N2-O2. It is shown that there is good agreement between our calculations and experimental data for all cases of energy transfer considered.Key words. Ionosphere (Auroral ionosphere; ion chemistry and composition). Atmospheric composition and structure (Aciglow and aurora).

Vibrational energy transfer. Collisional quenching of competitive unimolecular reactions

1968 ◽  
Vol 46 (2) ◽  
pp. 341-343 ◽  
Author(s):  
D. C. Tardy ◽  
C. W. Larson ◽  
B. S. Rabinovitch
Keyword(s):  
Vibrational Energy ◽  
Heat Bath ◽  
Polyatomic Molecules ◽  
Unimolecular Reaction ◽  
Collisional Quenching ◽  
Kcal Mole ◽  
Vibrationally Excited ◽  
Reaction Systems ◽  
A Value ◽  
Collisional Deexcitation

A technique is described for the study of collisional deexcitation of highly vibrationally excited polyatomic molecules by use of externally activated competitive unimolecular reaction systems. This method has some advantages and is illustrated by the decomposition of chemically activated hexyl-3 radicals in the presence of H2 and CF4 as heat bath molecules. The former removes ~1.2 kcal mole−1 per successful collision; while for the latter a value in excess of 4.6 kcal is found so that CF4 behaves operationally like a strong collider.

scholarly journals Picosecond Anti-Stokes Raman Excitation Profiles as a Method for Investigating Vibrationally Excited Transients

1999 ◽  
Vol 19 (1-4) ◽  
pp. 335-341 ◽  
Author(s):  
Hiromi Okamoto ◽  
Takakazu Nakabayashi ◽  
Mitsuo Tasumi
Keyword(s):  
Vibrational Energy ◽  
Vibrational Modes ◽  
Vibrational States ◽  
Vibrationally Excited ◽  
Quantum Numbers ◽  
Trans Stilbene ◽  
Raman Process ◽  
Vibrationally Hot Molecules ◽  
Raman Excitation Profiles ◽  
Anti Stokes

A method for estimating vibrational quantum numbers of vibrationally excited transients in solution is proposed. In this method, we calculate anti-Stokes Raman excitation profiles (REPs) which are characteristic of the initial vibrational states involved in the Raman process, and compare them with observed anti-Stokes intensities. We have applied this method to vibrationally hot molecules of canthaxanthin in the So state and those of trans-stilbene in the S1 state. For canthaxanthin, it has been found that the vibrationally excited transients are for the most part on the ν=1 level of the C═C stretching mode, and that excess vibrational energy is statistically distributed among all intramolecular vibrational modes. As for S1 stilbene, vibrational transients are shown to be mostly on the ν=1 level for two vibrational modes examined, while the excess vibrational energy is probably localised on the olefinic C═C stretching mode.

IR spectrum of highly vibrationally excited osmium tetraoxide in the region of strong nonlinear interaction of vibrational modes

1990 ◽  
Vol 94 (4) ◽  
pp. 1294-1297 ◽  
Author(s):  
O. V. Boyarkin ◽  
S. I. Ionov ◽  
A. A. Stuchebrukhov ◽  
V. N. Bagratashvili ◽  
M. S. Dzhidzhoev
Keyword(s):  
Ir Spectrum ◽  
Nonlinear Interaction ◽  
Vibrational Modes ◽  
Vibrationally Excited ◽  
Osmium Tetraoxide

scholarly journals Pump- And Probe-Wavelength Dependencies of Picosecond Anti-Stokes Raman Spectrum of Trans-Stilbene in the S1 State

1999 ◽  
Vol 19 (1-4) ◽  
pp. 75-78 ◽  
Author(s):  
Takakazu Nakabayashi ◽  
Hiromi Okamoto ◽  
Mitsuo Tasumi
Keyword(s):  
Vibrational Relaxation ◽  
Vibrational Energy ◽  
Wavelength Dependence ◽  
Relaxation Dynamics ◽  
Vibrationally Excited ◽  
Time Resolved ◽  
Probe Wavelength ◽  
Trans Stilbene ◽  
Pump And Probe ◽  
Anti Stokes

Vibrational relaxation dynamics of trans-stilbene in the S1 state immediately after photoexcitation is studied by picosecond time-resolved anti-Stokes Raman spectroscopy with several pump and probe wavelengths. Pump-wavelength dependence of the anti- Stokes spectrum indicates that, when pump photons with high excess energy (≈5200cm-1) are used, the anti-Stokes Raman bands at 0 ps delay time arise from vibrationally excited transients with excess vibrational energy not thermally distributed in the molecule. Probe-wavelength dependence suggests that the vibrationally excited transients at 0 ps are mostly on the lowest excited vibrational levels, as far as the olefinic C═C stretching and the C–Ph stretching modes are concerned. The vibrational relaxation process of S1trans-stilbene is discussed on the basis of the observed results.

Vibrational Energy Transfer in Carbon Monoxide

1972 ◽  
Vol 50 (9) ◽  
pp. 889-897 ◽  
Author(s):  
P. H. Dawson ◽  
W. G. Tam
Keyword(s):  
Energy Exchange ◽  
Vibrational Energy ◽  
Transverse Flow ◽  
Vibration Energy ◽  
Excess Oxygen ◽  
Experimental Measurements ◽  
Energy Distributions ◽  
Vibrationally Excited ◽  
Population Distributions

The role of V–V processes in vibrationally excited CO systems in the longitudinal and transverse flow chemical lasers is studied. Initial vibrational energy distributions of CO formed by the O + CS reaction are deduced from chemiluminescent data using calculated values of the vibration energy exchange probabilities. The time evolution of the population distributions is then obtained by computer simulation. The results are compared with experimental measurements. The effects of excess oxygen and of "cold" CO on the population distributions are also discussed.

Vibrational energy distribution in HF formed by elimination from activated CH3CF3 and CH2CF2

1970 ◽  
Vol 48 (18) ◽  
pp. 2919-2930 ◽  
Author(s):  
P. N. Clough ◽  
J. C. Polanyi ◽  
R. T. Taguchi
Keyword(s):  
Rate Constants ◽  
Vibrational Energy ◽  
Flow System ◽  
Relative Rate ◽  
Elimination Reaction ◽  
Vibrationally Excited ◽  
Vibrational Levels ◽  
Relative Rate Constants ◽  
Fast Flow ◽  
Vibrational Energy Distribution

The combination–elimination reaction CH3 + CF3 → CH3CF3† → CH2CF2 + HF has been studied in a fast-flow system. Infrared chemiluminescence arising from the HF product has been observed from vibrational levels v = 1–4, and relative rate constants, k(v), have been obtained for HF formation in these levels. A study has also been made of the reaction CH2CF2 + Hg*(63P1) → CHCF + HF + Hg(61S0), which has been found to produce vibrationally-excited HF. Relative rate constants k(v) for vibrational levels v = 1–4 have been obtained. It appears that channelling of the potential energy into HF vibration, in the course of the elimination step, is more efficient in the first than in the second of these reactions. In the second reaction HF is eliminated with considerable rotational excitation.

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