Role of XeF as an intermediate in the photochemical synthesis of XeF/sub 2/ in flash-photolyzed Xe/Ar/F/sub 2/ mixtures

Journal Article · Thu Mar 18 04:00:00 EST 1982 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100395a018· OSTI ID:5611253

Messing, I; Smith, A L

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/ 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.

• Research Organization: Drexel Univ., Philadelphia, PA
• OSTI ID: 5611253
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 86:6; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
ARGON
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DECOMPOSITION
DISPERSIONS
ELEMENTS
ENTHALPY
EXPERIMENTAL DATA
FLUIDS
FLUORESCENCE
FLUORIDES
FLUORINE
FLUORINE COMPOUNDS
FORMATION HEAT
GASES
HALIDES
HALOGEN COMPOUNDS
HALOGENS
INFORMATION
KINETICS
LASERS
LUMINESCENCE
MIXTURES
NONMETALS
NUMERICAL DATA
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PHYSICAL PROPERTIES
RARE GAS COMPOUNDS
RARE GASES
REACTION HEAT
REACTION INTERMEDIATES
REACTION KINETICS
SPECTROSCOPY
SYNTHESIS
THERMODYNAMIC PROPERTIES
XENON
XENON COMPOUNDS
XENON FLUORIDES