F + H2 reaction

The first mfonnation on the HE vibrational distribution was obtained in two landmark studies by Pimentel [39] and Polanyi [24] in 1969 both studies showed extensive vibrational excitation of the HE product. Pimental found that tire F + H2 reaction could pump an infrared chemical laser, i.e. the vibrational distribution was inverted, with the HF(u = 2) population higher than that for the HF(u = 1) level. A more complete picture was obtained by Polanyi by measuring and spectrally analysing tlie spontaneous emission from vibrationally excited HE produced by the reaction. This infrared chemiluminescence experiment yielded relative populations of 0.29, 1 and 0.47 for the HF(u =1,2 and 3)... 

Figure A3.7.7. Two-dimensional contour plot of the Stark-Wemer potential energy surface for the F + H2 reaction near the transition state. 0 is the F-H-H bend angle.

F( Pjy,) state but concludes that the adiabatic picture is largely correct. The issue of whether a reaction can be described by a single Bom-Oppenlieimer surface is of considerable interest in chemical dynamics [10], and it appears that the effect of multiple surfaces must be considered to gain a complete picture of a reaction even for as simple a model system as the F + H2 reaction. 

With spectroscopic detection of the products, the angular distribution of the products is usually not measured. In principle, spectroscopic detection of the products can be incorporated into a crossed-beam scattering experiment of the type described in section B2.3.2. There have been relatively few examples of such studies because of the great demands on detection sensitivity. The recent work of Keil and co-workers (Dhannasena et al [16]) on the F + H2 reaction, mentioned in section B2.3.3, is an excellent example of the implementation... 

Recently, the state-selective detection of reaction products tluough infrared absorption on vibrational transitions has been achieved and applied to the study of HF products from the F + H2 reaction by Nesbitt and co-workers (Chapman et al [7]). The relatively low sensitivity for direct absorption has been circumvented by the use of a multi-pass absorption arrangement with a narrow-band tunable infrared laser and dual beam differential detection of the incident and transmission beams on matched detectors. A particular advantage of probing the products tluough absorption is that the absolute concentration of the product molecules in a given vibration-rotation state can be detenuined. 

In most tiieoretical treatments of the collision dynamics, the reaction is assumed to proceed on a single PES. However, reactions involving open-shell reagents of products will involve several PESs. For example, in the F + H2 reaction, discussed in section B2.3.2.4. tluee PESs emanate from the separated reagents, of which only... 

S.L. Latham, J.F. McNutt, R.E. Wyatt, M.J. Redmon, Quantum dynamics of the F+H2 reaction Resonance models, and energy and flux distributions in the transition state, J. Chem. Phys. 69 (1978) 3746. 

V. Aquilanti, S. Cavalli, D. De Fazio, A. Volpi, A. Aguilar, J.M. Lucas, Benchmark rate constants by the hyperquantization algorithm. The F+H2 reaction for various potential energy surfaces Features of the entrance channel and of the transition state, and low temperature reactivity, Chem. Phys. 308 (2005) 237. 

Jaquet, R. (1987). Investigations with the finite element method. II. The collinear F + H2 reaction, Chem. Phys. 118, 17-23. 

Weaver, A. and Neumark, D.M. (1991). Negative ion photodetachment as a probe of bimolecular transition states the F + H2 reaction, Faraday Discuss. Chem. Soc. 91, 5-16. 

For the F+H2 reaction high levels of theory are required. The Hartree-Fock limit for the classical barrier height is about 67 kJ/mol [J. Phys. Chem. 89, 5336 (1985)], that is, almost ten times larger than the exact value ... 

Table 6.2 Properties of the reactants and the activated complex for the F + H2 reaction. Data from an ab initio potential energy surface [J. Ghem. Phys. 104, 6515 (1996) and Chem. Phys. Lett. 286, 35 (1998)].

Many semi-classical and quantum mechanical calculations have been performed on the F + H2 reaction, mainly being restricted to one dimension [520, 521, 602]. The prediction of features due to quantum-mechanical interferences (resonances) dominates many of the calculations. In one semi-classical study [522], it was predicted that the rate coefficient for the reaction F (2P1/2) + H2 is about an order of magnitude smaller than that for F(2P3/2) 4- H2, which lends support to the conclusion [508] that the experimental studies relate solely to the reaction of ground state fluorine atoms. Information theory has been applied to many aspects of the reaction including the rotational energy disposal and branching ratios for F + HD [523, 524] and has been used for transformation of one-dimensional quantum results to three dimensions [150]. Linear surprisal plots occur for F 4- H2(i> = 0), as noted before, but non-linear surprisal plots are noted in calculations for F + H2 (v < 2) [524],... 

J.N.L. Connor, W. Jakubetz, J. Manz, Exact quantum transition-probabilities by state path sum method—CoUinear F -F H2 reaction. Mot Phys. 29 (2) (1975) 347-355. 

Theoretical study of the F + H2 reaction in the pres- 719 ence of a strong laser field... 

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