Theory of V–V and V–T/R energy transfer for HF (n=1 to 7)+HF (0)

Billing, Gert Due; Poulsen, Lise Lotte

doi:10.1063/1.435632

Cited by 90 publications

(10 citation statements)

References 48 publications

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“…66,112 Billing's calculations found no evidence of high rotational state population, while the calculations by Wilkins and Thompson indicate that vibrational-rotational energy transfer is a relatively efficient process and that multiquantum deactivations occur on a fairly regular basis. In particular, Thompson 104 calculated state-to-state collsion cross sections for HF(vϭ4,Jϭ20) relaxation by He and reported 3.3, 6.7, 10.7, 18.5, and 38.24 a.u.…”

Section: Relevant Theoretical Studiesmentioning

confidence: 97%

“…A modified Stern-Volmer analysis was applied to the quenching data. Table 6 compares the experimentally determined rate constants for HF self-relaxation with a variety of other experiments, 53-63 relevant calculations, [64][65][66] and the standard kinetics packages. [1][2][3][4] The agreement for vϭ1 -7 is, in general, excellent and k 8 is well established.…”

Section: Self-relaxation (Deactivation By Ground State Hf)mentioning

confidence: 99%

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A Review of Recent Experiments and Calculations Relevant to the Kinetics of the HF Laser

Manke

Hager

2001

Journal of Physical and Chemical Reference Data

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An abbreviated review of rate coefficients relevant to HFI laser kinetics modeling is presented. The literature has been surveyed from the last published review in 1983 to the present. Updated HF Einstein emission coefficients are tabulated. This brief summary of a more detailed review addresses rate coefficients relevant to HIF generation, reactive quenching, self-relaxation, and vibrational relaxation by a selection of atoms and molecules. In addition, a review of recent experiments and theoretical calculations relevant to the role of rotational non-equilibrium in HF lasers is presented. A list of recommended temperature dependent expressions for critical reaction rate coefficients is given. INTRODUCTIONSince its invention in the mid-1960's, the HF laser system has been extensively studied and developed to the point where megawatt-class devices can be built. In fact, most of the research in the recent past has focused on large-scale laser technology demonstrations. Despite the enormous effort expended to accomplish this, a complete understanding of all facets of HF laser performance is still evolving and is not complete. For example, research continues into the role of reagent mixing and heat transfer between the fluids and the construction material of the device. Combustor instabilities and other complex, transient, fluid dynamical features also impede our understanding of the laser's performance.The only way to achieve insight into the details of the HF laser is to employ computational fluid dynamical (CFD) codes that can integrate the complex fluid properties with the myriad chemical reactions that occur in the laser cavity. Unfortunately (although perhaps not surprisingly considering the complexity of the problem), CFD codes have had limited success at accurately modeling real HIF laser systems. As a result, both the laser performance data and the reaction rate constants used to baseline the models have come under increased scrutiny in recent years. This scrutiny has uncovered serious questions about the kinetics package that have yet to be answered conclusively. These questions include the importance of rotational nonequilibrium, the magnitude of various quenching processes, the role of three body and heterogeneous fluorine atom recombination, and other fundamental properties such as Einstein coefficients.The main topics of this report (in order of their presentation) are Einstein coefficients and relevant kinetic measurements. It is not within the scope of this document to discuss fluid dynamics issues, such as recently developed 3 dimensional computational fluid dynamics (CFD) codes or new algorithms to model mixing or optical resonators.

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Section: Relevant Theoretical Studiesmentioning

confidence: 97%

Section: Self-relaxation (Deactivation By Ground State Hf)mentioning

confidence: 99%

A Review of Recent Experiments and Calculations Relevant to the Kinetics of the HF Laser

Manke

Hager

2001

Journal of Physical and Chemical Reference Data

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“…The interaction potential used was obtained as an analytical fit to the ab initio points computed by Yarkony and collaborators 1281, with empirical additions that allowed inclusion of long-range dispersion terms. Further extension to self relaxation of vibrationally excited H F has also been considered by the same authors [29] essentially using the same theoretical method. In comparing the computed results of process (1) with experiments they found indeed satisfactory agreement over the range of temperatures examined and pointed out the importaxe of long lived complexes in redistributing molecular internal energy at low collision velocities, as already observed experimentally [30].…”

Section: Introductionmentioning

confidence: 90%

“…Alternatively, at a gas pressure of 1 atm, T is given in sec as In a gas in translational equilibrium, the rate constants are in turn obtained as the Laplace transforms of a function proportional to the inelastic cross section for the relevant process [29]:…”

Section: Relaxation Timesmentioning

confidence: 99%

Vibrationally inelastic scattering and relaxation times in gaseous HF

Gianturco¹,

Lamanna

Battaglia³

1981

Int J of Quantum Chemistry

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AbstractsA numerical fit to computed ab initio points of the HF-HF potential energy surface is here employed in its simplest spherical form to solve the corresponding close-coupling equations that yield vibrationally inelastic collision cross sections for the V / T process in the gas phase. The existence of a deep potential well in the interaction is examined here for its effect on near-threshold cross section behavior and evidence is found, through the present calculations, for the relative importance of several (orbiting) shape resonances that contribute to the Ql,o cross sections at low collision energies (50.4 eV). The bearing of such lengthened interaction times on the corresponding low temperature relaxation times is shown in the ensuing calculation of p~ in the T range between 300 and 4000 K. In spite of the simplicity of the present model, quite good agreement is in fact found with experiments in the low-T region, while the lack of V , R / T coupling explains the departure of the computed p~, above 1000 K, from the experimental findings.Une adaptation numerique aux points d'une surface de potentiel HF-HF calcults ab initio est utilisie dans sa forme spherique la plus simple pour resoudre les equations de couplage fort correspondantes, qui fournissent des sections efficaces intlastiques du point de vue des vibrations pour le processus V / T dans la phase gazeuse. L'existance d'un puits de potentiel profond dans I'interaction est examinee du point de vue de son effet pour le comportement de la section efficace prks du seuil. Nos calculs dtmonstrent I'importance relative de plusieurs resonances de forme qui contribuent aux sections efficaces Ql,a ii des energies de collision basses (50.4eV). L'influence de ces temps d'interaction prolongis sur les temps de relaxation correspondants pour les basses temperatures est demontrte dans un calcul de pr pour T entre 300 et 400 K. Malgrt la simplicit6 du modde on trouve un accord assez bon avec les donntes experimentales pour les basses temperatures. D'autre part I'absence de couplage V , R / T explique la difference entre les valeurs de PT calcultes au-dessus de 1000 K et les valeurs exptkimentales.Eine numerische Anpassung zu ab-initio-berechneten Punkten auf einer HF-HF-Potentialenergieobedache wird in ihrer einfachsten spharischen Form benutzt, urn die entsprechenden Gleichungen fur starke Kopplung zu losen, die inelastische Schwingungsquerschnitte fur das V/ T-Prozess in der Gasphase liefern. Die Existenz eines tiefen Potentialtopfes in der Wechselwirkung wird mit Riicksicht auf seinen Effekt auf das Verhalten des Querschnitts in der Nahe der Schwelle untersucht. Unsere Berechnungen zeigen die relative Bedeutung von mehreren "Shape"-Resonanzen, die zu den Ql

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“…These new laser double resonance measurements also provide the temperature dependence of the total selfrelaxation rate for both HF(v = 1) and HF(v = 2), The former has been extensively studied by a variety of techniques,7-IO but the latter has not been investigated previously except at room temperature. 4 ,5(b),6 Data on the total relaxation rate and the magnitudes of the rates for individual pathways provide a sensitive test of theoretical models, and, in particular, we compare our measurements on HF(v = 1 and 2) with classical ll ,12 and semiclassical 13 trajectory calculations. The entire body of data now available on self-relaxation of HF(v = 1-5) between 300 and 700 K forms a consistent picture of the energy transfer mechanism in which the variation of the energetics of V-V and V-T, R processes with initial vibrational state determines their relative importance.…”

Section: Introductionmentioning

confidence: 99%

Rates and pathways of vibrational self-relaxation of HF(v=2) between 300 and 700 K

Robinson

Pearson

Copeland

et al. 1985

The Journal of Chemical Physics

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The vibrational quantum number dependence of the collisional lifetime in nitric oxide selfrelaxation up to v'=25 A direct determination of the role of vibrationtovibration energy transfer in HF(v=3,4) selfrelaxation J. Chem. Phys. 84, 220 (1986); 10.1063/1.450174Vibrational relaxation of HF(v = 3, 4, 5) between 300 and 700 K The temperature dependencies of the total self-relaxation rate constants for the vibrational deactivation ofHF(v = 2) and HF(v = 1) and the state-to-state vibrationto-vibration (V-V) and vibration-to-translation-and-rotation (V-T,R) energy transfer components of the HF(v = 2) self-relaxation process are measured using the overtone vibration excitation-laser double resonance technique. The total self-relaxation rate constants vary inversely with temperature. The much weaker temperature dependence of HF(v = 2) self-relaxation compared to that of HF(v = I) arises from the significant role of the V-V energy transfer route. Competition between energetics and collision duration results in a weaker inverse variation with temperature for the slightly endothermic V-V route than for the exothermic V-T,R route for HF(v = 2).The branching ratio for V-V energy transfer increases slightly with temperature and the data suggest that two quantum relaxation processes constitute no more than 10% of the total self-relaxation of HF(v = 2). The available temperature dependence data on self-relaxation of HF(v = 1-5) form a consistent picture in which the energetics of the V-V and V-T,R relaxation pathways control their relative contributions to the total energy transfer.by direct overtone vibration excitation at -1.3 f.L. A fast ( -5 ns) InAs detector in conjunction with a transient 780

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Theory of V–V and V–T/R energy transfer for HF (n=1 to 7)+HF (0)

Cited by 90 publications

References 48 publications

A Review of Recent Experiments and Calculations Relevant to the Kinetics of the HF Laser

A Review of Recent Experiments and Calculations Relevant to the Kinetics of the HF Laser

Vibrationally inelastic scattering and relaxation times in gaseous HF

Rates and pathways of vibrational self-relaxation of HF(v=2) between 300 and 700 K

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