Role of xenon monofluoride as an intermediate in the photochemical synthesis of xenon difluoride in flash-photolyzed xenon-argon-fluorine mixtures

.. XeF (k/sub 7/,k/sub -7/) was calculated from statistical thermodynamics to be K/sub eq/ = 2.22 x 10/sup -21/ cm/sup 3/ at 298 K, and values of k/sub 7/ and k/sub -7/ show that equilibrium between F and XeF was rapidly established. The buildup and decay of XeF was monitored in the B-X (323 nm) and D-X (253.5 nm) transitions; the buildup of XeF/sub 2/ was detected by its absorption at 253.5 and 235 nm. The heat of formation of XeF(g) was calculated to be ..delta..H/sub f//sup 0/ (298) = + 15.5 kcal mol/sup -1/. Although the average Xe-F bond energy in XeF/sub 2/ is 32 kcal mol/sup -1/, the energy released in adding the first F atom to Xe is only 3.4 kcal; thus, the reaction XeF + F/sub 2/ ..-->.. XeF/sub 2/ + F (k/sub 10/) is exothermic by 23 kcal. This reaction explains the observed kinetics at low pressures and XeF densities if k/sub 10/more » approx. 6 x 10/sup -16/cm/sup 3/s/sup -1/. For XeF densities of approx. 1-5 x 10/sup 13/ cm/sup -3/, bimolecular steps such as XeF + XeF ..-->.. FeF/sub 2/ + Xe become important.« less -->
ISSN: 1541-5740
0022-3654
DOI: 10.1021/j100395a018
Přístupová URL adresa: https://explore.openaire.eu/search/publication?articleId=doi_________::48ac360404de1d799676f3e588fc6c2b
https://doi.org/10.1021/j100395a018
Přírůstkové číslo: edsair.doi...........48ac360404de1d799676f3e588fc6c2b
Autor: Allan L. Smith, Itzhak Messing
Rok vydání: 1982
Předmět:
Zdroj: The Journal of Physical Chemistry. 86:927-932
ISSN: 1541-5740
0022-3654
DOI: 10.1021/j100395a018
Popis: The fluorine in Xe/F/sub 2/ and Xe/Ar/F/sub 2/ mixtures was photodissociated, and the resulting transient species were monitored by photographic and photoelectric UV kinetic absorption spectroscopy and by laser fluorescence. The number density equilibrium constant for the reversible reaction Xe + F ..-->.. XeF (k/sub 7/,k/sub -7/) was calculated from statistical thermodynamics to be K/sub eq/ = 2.22 x 10/sup -21/ cm/sup 3/ at 298 K, and values of k/sub 7/ and k/sub -7/ show that equilibrium between F and XeF was rapidly established. The buildup and decay of XeF was monitored in the B-X (323 nm) and D-X (253.5 nm) transitions; the buildup of XeF/sub 2/ was detected by its absorption at 253.5 and 235 nm. The heat of formation of XeF(g) was calculated to be ..delta..H/sub f//sup 0/ (298) = + 15.5 kcal mol/sup -1/. Although the average Xe-F bond energy in XeF/sub 2/ is 32 kcal mol/sup -1/, the energy released in adding the first F atom to Xe is only 3.4 kcal; thus, the reaction XeF + F/sub 2/ ..-->.. XeF/sub 2/ + F (k/sub 10/) is exothermic by 23 kcal. This reaction explains the observed kinetics at low pressures and XeF densities if k/sub 10/more » approx. 6 x 10/sup -16/cm/sup 3/s/sup -1/. For XeF densities of approx. 1-5 x 10/sup 13/ cm/sup -3/, bimolecular steps such as XeF + XeF ..-->.. FeF/sub 2/ + Xe become important.« less
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