MULTIPHOTON DISSOCIATION PRODUCTS FROM HALOGENATED HYDROCARBONS

Journal Article · Tue Nov 01 00:00:00 EST 1977 · Chemical Physics

OSTI ID:1004778

Sudbo, Aa S; Schulz, P A; Grant, E R; Lee, Y T

The recent interest in multiphoton dissociation (MPD) of polyatomic molecules has revealed quite a bit of confusion as to what the major dissociation channels of some molecules are, and whether the dissociation process can be described by a statistical, e.g., RRKM, theory of unimolecular reactions. In a gas cell experiment an experimenter often finds great difficulties in answering questions such as: do vibrationally excited molecules react with one another, how do reactions involving free radicals produced in the dissociation proceed, can these radicals decompose further in the presence of the laser field, and does the detection method used actually probe the primary dissociation channel. Using the molecular beam setup previously described, we have overcome most of these difficulties. We have studied MPD of a number of compounds, mainly halogenated methanes, ethanes and ethylenes, and identified their major dissociation channels. To identify an MPD product, we realize that a unique set of ratios between mass spectrometer signals of various ion fragments must first be established for a given molecular species or radical, and preferably the velocity distributions of the dissociation products should be measured and checked for consistency. In our setup, we could measure both angular and time-of-flight distributions for the fragments, and pereorm this check. The low density of molecules in the beam and the extremely low duty cycle in our experiment prevented us from observing the competing minor channels which have very small branching ratios (< 0.1).

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Chemical Sciences Division
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1004778
• Report Number(s): LBL-6966
• Journal Information: Chemical Physics, Journal Name: Chemical Physics; ISSN 0301-0104; ISSN CMPHC2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
99 GENERAL AND MISCELLANEOUS
BRANCHING RATIO
DETECTION
DISSOCIATION
LASERS
MASS SPECTROMETERS
MOLECULAR BEAMS
MOLECULES
ORGANIC HALOGEN COMPOUNDS
PROBES
RADICALS
VELOCITY