Multiphoton dissociation of SF/sub 6/ by a molecular beam method

Journal Article · Thu May 01 00:00:00 EDT 1980 · J. Chem. Phys.; (United States)

OSTI ID:5471312

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

The dynamics of infrared multiphoton excitation and dissociation of SF/sub 6/ has been investigated under collision-free conditions by a crossed laser--molecular beam method. In order to understand the excitation mechanism and to elucidate the requirements of laser intensity and energy fluence, a series of experiments have been carried out to measure the dissociation yield dependences on energy fluence, vibrational temperature of SF/sub 6/, the pulse duration of the CO/sub 2/ laser, and the frequency in both one and two laser experiments. Translational energy distributions of the primary dissociation product SF/sub 5/, measured by time-of-flight and angular distributions and the dissociation lifetime of excited SF/sub 6/ as inferred from the observation of secondary dissociation of SF/sub 5/ into SF/sub 4/ and F during the laser pulse suggest that the dynamics of dissociation of excited molecules is dominated by complete energy randomization and rapid intramolecular energy transfer and can be adequately described by RRKM theory. An improved phenomenological model including the initial intensity dependent excitation, a rate equation describing the absorption and stimulated emission of single photons, and the unimolecular dissociation of excited molecules is constructed based on available experimental results. Our studies show that although the energy fluence of the laser determines the dissociation yield of molecules in the quasicontinuum, the role played by the intensity of the laser in multiphoton dissociation is more significant than just that of overcoming the intensity dependent absorption in the lowest levels. Once molecules are excited beyond the dissociation energy, the average level of excitation of the dissociating molecules will be significantly influenced by the laser intensity for a given energy fluence when the rate of decomposition starts to compete with the rate of up-excitation.

• Research Organization: Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
• OSTI ID: 5471312
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 72:9; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
BEAMS
CHEMICAL REACTIONS
DECOMPOSITION
DISSOCIATION
ELECTROMAGNETIC RADIATION
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITATION
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
INFRARED RADIATION
LASER RADIATION
MOLECULAR BEAMS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RADIATIONS
SULFUR COMPOUNDS
SULFUR FLUORIDES