Vibrational Deactivation of HF(<i>v</i>=1) in Pure HF and in HF-Additive Mixtures

Hancock, J. K.; Green, W. H.

doi:10.1063/1.1678109

Cited by 115 publications

(14 citation statements)

References 69 publications

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“…In particular, such forces were invoked in the 1970s to explain the rapid rates observed for the vibrational relaxation of HF(v = 1) both in HF-HF collisions 8,9 and in collisions with H 2 O. 8b, [9][10][11] In such cases, it is less likely that IVR in any complex that is formed will occur faster than re-dissociation to the collision partners in their original vibrational states. Consequently, the mechanism for vibrational relaxation must take account of the competition between IVR in the complex and its re-dissociation without loss of the initial vibrational excitation.…”

Section: Introductionmentioning

confidence: 99%

The relaxation of OH (v = 1) and OD (v = 1) by H2O and D2O at temperatures from 251 to 390 K

McCabe

Rajakumar

Marshall

et al. 2006

Phys. Chem. Chem. Phys.

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We report rate coefficients for the relaxation of OH(v = 1) and OD(v = 1) by H 2 O and D 2 O as a function of temperature between 251 and 390 K. All four rate coefficients exhibit a negative dependence on temperature. In Arrhenius form, the rate coefficients for relaxation (in units of 10 À12 cm 3 molecule À1 s À1 ) can be expressed as: for OH ( , 1977, 66, 4758), in order to estimate the rates of intramolecular energy transfer from the OH (OD) vibration to other modes in the complexes in order to explain the measured relaxation rates-assuming that relaxation proceeds via the hydrogen-bonded complexes.

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Section: Introductionmentioning

confidence: 99%

The relaxation of OH (v = 1) and OD (v = 1) by H2O and D2O at temperatures from 251 to 390 K

McCabe

Rajakumar

Marshall

et al. 2006

Phys. Chem. Chem. Phys.

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“…At the low temperatures involved it is probably dimerization which is responsible (28). Linear extrapolations of HF relaxation data, measured at mole fractions as low as 0.00 1, to X = I differ very much from the results for pure HF, thus indirectly indicating non-linearities (29). Similarly for H, (21).…”

Section: H Comparison With Experimentsmentioning

confidence: 86%

A simple reason for non-linear mixture rules in chemical kinetics. Part 1. Vibrational relaxation of diatomic molecules

Carruthers¹,

Teitelbaum²

1985

Can. J. Chem.

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CHRIS CARRUTHERS and HESHEL TEITELBAUM. Can. J. Chem. 63, 38 1 (1 985). The generalized rate law for the vibrational relaxation of diatomic molecules is extended to include inert collision partners. V-V energy transfer processes are accounted for explicitly as are thermal effects. The molecules are treated as Morse oscillators as far as energetics are concerned; however, the microscopic rate constants are Landau-Teller type. It is found that the phenomenon of non-linear mixture rules arises when experimental data are forced to fit a first-order rate law. The persistence of V-V processes at times well-advanced into the relaxation zone is responsible for deviations from linearity. The nonlinearities are most pronounced at high temperatures, and can be avoided only by using extremely dilute mixtures. Several sources of ambiguity are pointed out. The type of excitation method influences the initial deviation from a Boltzmann distribution and plays a crucial role in determining the importance of V-V processes and hence the degree of non-linearity. 'Thus, when the initial distribution is Boltzmann as in shock waves, the mixture rule is found to be absolutely linear for the vibrational relaxation of diatomic molecules.Several examples, heretofore not recognized as such, are pointed out in the literature.CHRIS CARRUTHERS et HESHEL TEITELBAUM. Can. J. Chem. 63, 381 (1985). Dans le but d'inclure des partenaires inertes impliquks dans des collisions, on a Ctendu la loi gCnCralisCe de vitesse des relaxations vibrationnelles des molCcules diatomiques. On peut interprkter explicitement tant les effets thermiques que les processus de transferts d'knergie V-V. En autant que les Cnergies sont concernCes, on traite les molCcules comme des oscillateurs de Morse; toutefois, les constantes microscopiques de vitesse sont du type Landau-Teller. Lorsqu'on force les donntes expCrimentales a obCir B une loi de vitesse du premier ordre, on observe que le phCnomkne des rkgles de mClanges non-IinCaires se dCveloppe. C'est la persistance des processus V-V, B des temps bien avancCs dans la zone de relaxation, qui provoque des dCviations de la linCaritC. Les non-IinCaritCs sont plus prononcCes B hautes tempCratures et on peut les Cviter uniquement en utilisant des mClanges extrkmement diluCs. On identifie plusieurs sources d'ambiguitk. La mCthode d'excitation influence la deviation initiale, par rapport B la distribution de Boltzmann, et elle joue un r81e crucial dans la dCtermination de I'importance des proccssus V-V et, par conskquent, dans le degrC de non-IinCaritC. Donc, lorsque la distribution initiale est du type Boltzmann, comme dans les ondes de choc, on trouve que la rkgle des mClanges est absolument IinCaire pour la relaxation vibrationnelle des molCcules diatomiques.On a relevC, dans la IittCrature, plusieurs exemples qui n'avaient pas CtC reconnus comme tels.[

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“…However, in view of the fact that the degree of laser excitation is rarely known, this conclusion is not certain, and it would be worthwhile checking the data. Even though they produce distinctly different initial distributions, both laser excitation and chemical activation can produce the entire range of values of 6. Particular values of a are suggested (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…The ambiguity is cleared up when measurements are made at morc than one //T'. experimentalist c o~~l d determine both y and T , as an alternative method to manipulating 6. We note that it may not be necessary to vary the time scale over many orders of magnitude: even for y = 10'' where the interesting region of t /~' varies from 1.74 X lo-' to 2.63, the absolute time scale, t, only varies by a factor of 4.7 (the region of rapid rise in Fig We note further that r /~ can be written at N~/ N T , where NT is just (k,,,, -k,,,l)-'.…”

Section: Shock Tubesmentioning

confidence: 99%

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Solutions of the generalized rate law for vibrational relaxation of a pure diatomic gas

Teitelbaum¹

1983

Can. J. Chem.

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61. 1276 (1983). Thc gcncralizcd ratc law for tlic relaxation of thc vibrational cncrgy of a p~11.c di;~toriiic gas. AB, dcrivcd carlicr, is solvcd analytically for a varicty of initial conditions corscsponding to shock tubc, lascr-cxcitcd fluorcsccncc, and chcmical activation cxpcrimcnts. Thc rcsulting cxprcssions can bc uscd to casily prcdict wlicthcr a givcn systcm will rclax according to a V-V or a T-V mechanism or both. Thc initial conditions and thc rnolccul;~s anharmonicity arc shown to bc as important, if not morc important, for this purposc than thc ratio of T-V ant1 V-V ratc constants. Bchind shock wavcs thc cncrgy rclaxcs cxponcntially with a T-V timc constant. Thc initial distribution rcmains Boltzmann. In I:~scr or chcmical activation cxpcrimcnts thc cncrgy does not rclax cxponcntially, lcading to phcnomcnological timc "constants"which arc not constant in timc and prcvcnt dircct comparisons with shock tubc data. It is only aftcr an incubation pcriod during which thc vibrational cncrgy is rcdistributcd via V-V proccsscs that thc cncrgy tlicn cxchangcs with translational cncrgy and dccays. Prescriptions arc givcn to cxtract T-V ancl V-V ratc constants from such data. Thc initial tlcgrcc of lascr excitation, u . and the timc regime probcd, 117, must bc known for this purposc. Howevcr, whcn dircct ovcrtonc cxcitation is uscd, a carcful choice of a can lead to extraction of the T-V constant directly. Even though thc vibrational cncrgy itself does not rclaxcxponcntially, it is shown that the mean energy. E / h v 1 , and the mean sclu~~rcci encrgy, ~' / ( l r v ' ) ' , rclax in such a way that plusieurs excitations par laser ou par reaction chimique dCcritcs dans la literature est donne. 11 est analysd selon les conditions initiales des experiences individuelles. En gCnCrale on trouve que plus sCvtre I'excitation et que plus elcvCs les nombrcs quantiques des niveaux excitCs, alors plus de caracttrc V-V aura la relaxation. L'Cquation "master" dCcrivant le changcment des populations des niveaux vibrationels individuels par rapport au tcrnps cst simplifie pour le rCgime du temps qui correspond B la redistribution rapide V-V de I'Cnergie. Ceci mtne h unc technique simple pour extrapoler les repartitions des populations observees vers la repartition initialc produitc par une reaction chiniique. Unc integration numCrique montre qu'en ginerale la rCpartition s'applitit simultanemcnt avec un mouvnicnt du pic vers v = 0.

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Vibrational Deactivation of HF(v=1) in Pure HF and in HF-Additive Mixtures

Cited by 115 publications

References 69 publications

The relaxation of OH (v = 1) and OD (v = 1) by H2O and D2O at temperatures from 251 to 390 K

The relaxation of OH (v = 1) and OD (v = 1) by H2O and D2O at temperatures from 251 to 390 K

A simple reason for non-linear mixture rules in chemical kinetics. Part 1. Vibrational relaxation of diatomic molecules

Solutions of the generalized rate law for vibrational relaxation of a pure diatomic gas

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