The Cs(7 P )+H sub 2 r arrow CsH+H reaction. I. Angular scattering measurements by Doppler analysis

Journal Article · Sun Jul 01 04:00:00 EDT 1990 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.459543· OSTI ID:7098997

L'Hermite, J; Rahmat, G; Vetter, R ^[1]

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1. Laboratoire Aime Cotton, C. N. R. S. II, Bat. 505, 91405 Orsay-Cedex (France)

The Cs(7{ital P})+H{sub 2}{r arrow}CsH ({ital X} {sup 1}{Sigma}{sup +}) ({ital v}{double prime}=0,{ital J}{double prime})+H reaction has been studied in a crossed-beam experiment, with electronic excitation of Cs atoms and laser-induced fluorescence detection of CsH products. The Doppler technique has been applied to determine the center of mass angular scattering probability of CsH products, for all rotational levels between 1 and 14 (in {ital v}{double prime}=0) and for various values of the collision energy between 0.03 and 0.13 eV. We have used two complementary arrangements of the analysis laser beam: With a parallel'' arrangement (the laser beam is along the collision axis), the shape analysis of fluorescence profiles leads directly to the angular scattering probability but experimental constraints limit the range of measurements; with a perpendicular'' arrangement (the laser beam is perpendicular to the collision plane), fluorescence profiles are symmetrical and forward'' contributions cannot be separated from backward'' ones. However, extensive shape analyses have been performed with this perpendicular arrangement, since the direction of scattering was determined earlier by recording several profiles with the parallel arrangement. For the title reaction, it is shown unambiguously that, in the center of mass, CsH products scatter preferentially at small angle, in the forward direction with respect to the Cs initial velocity. The angular scattering probability varies with the collision energy but is independent of the rotational level of the product molecule (thus of its recoil velocity). These results are compatible with the harpooning mechanism which was suggested for the reaction.

• OSTI ID: 7098997
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 93:1; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ALKALI METAL COMPOUNDS
ALKALI METALS
ANGULAR DISTRIBUTION
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
ATOMIC BEAMS
BEAMS
CESIUM
CESIUM COMPOUNDS
CESIUM HYDRIDES
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
COLLISIONS
DISTRIBUTION
DOPPLER EFFECT
ELEMENTS
EMISSION SPECTROSCOPY
ENERGY RANGE
EV RANGE
FLUORESCENCE SPECTROSCOPY
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
METALS
MILLI EV RANGE
MOLECULAR BEAMS
MOLECULE COLLISIONS
NONMETALS
SPECTROSCOPY
YIELDS