Infrared multiphoton dissociation of heptafluoropropane

Journal Article · Thu Jul 30 00:00:00 EDT 1987 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100300a016· OSTI ID:6034289

Kato, S; Makide, Y; Tominaga, T; Takeuchi, K

The dissociation yield and branching ratio in CO/sub 2/-laser-induced multiphoton dissociation (MPD) of CF/sub 3/CF/sub 2/CHF/sub 2/ were studied as a function of irradiation frequency (979.7, 1037.4, and 1081.1 cm/sup -1/) and laser fluence (focal fluence < 20 J/cm/sup 2/). Br/sub 2/ was successfully employed to reveal the dissociation mechanisms by scavenging a number of primary and secondary dissociation fragments produced in the MPD. At low laser fluences the distributions of scavenged products were the same regardless of irradiation frequencies. The primary dissociation of CF/sub 3/CF/sub 2/CHF/sub 2/ was found to proceed mainly via the higher activation energy channels (i.e., C-C ruptures: CF/sub 3/CH/sub 2/CHF/sub 2/ ..-->.. C/sub 2/F/sub 5/ + CHF/sub 2/, and CF/sub 3/CF/sub 2/CHF/sub 2/ ..-->.. CF/sub 3/ + C/sub 2/HF/sub 4/) rather than via HF elimination (CF/sub 3/CF/sub 2/CHF/sub 2/ ..-->.. C/sub 3/F/sub 6/ + HF) in the authors experimental conditions. The observed branching ratio between the two C-C rupture channels (approx.2:1) agreed with the results obtained by RRKM calculation. A remarkable difference in product distribution with respect to the irradiation frequency was observed at higher laser fluences. This indicates that the secondary photolysis of primarily produced radicals within the laser pulse occurred significantly at higher fluences (i.e., C/sub 2/F/sub 5/ ..-->.. CF/sub 3/ + CF/sub 2/, CHF/sub 2/ ..-->..CF/sub 2/ + H, CF/sub 3/ ..-->.. CF/sub 2/ + F, and CHF/sub 4/ ..-->..CF/sub 2/ + CHF/sub 2/), depending strongly upon the irradiation frequencies.

• Research Organization: Univ. of Tokyo, Japan
• OSTI ID: 6034289
• Journal Information: J. Phys. Chem.; (United States), Vol. 91:16
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
FLUORINATED ALIPHATIC HYDROCARBONS
DISSOCIATION
PHOTOCHEMICAL REACTIONS
CARBON DIOXIDE LASERS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
EXPERIMENTAL DATA
INFRARED RADIATION
MULTI-PHOTON PROCESSES
PHOTOCHEMISTRY
PULSE TECHNIQUES
RADICALS
THERMODYNAMICS
CHEMICAL REACTIONS
CHEMISTRY
DATA
ELECTROMAGNETIC RADIATION
GAS LASERS
HALOGENATED ALIPHATIC HYDROCARBONS
INFORMATION
KINETICS
LASERS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RADIATIONS
REACTION KINETICS
YIELDS
400500* - Photochemistry