Translational energy dependence of the branching fraction and cross sections for the decay of collision complexes: K+CsF, RbF

Journal Article · Wed Dec 01 04:00:00 EST 1976 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.432933· OSTI ID:7238407

Stolte, S; Proctor, A E; Bernstein, R B

The reactions CsF+K..-->..KF+Cs-1.8 kcal mol/sup -1/ (I) and RbF+K..-->..KF+Rb+1.5 kcal mol/sup -1/ (II) have been studied by the crossed molecular beam technique over a range of relative translational energy E-bar/sub tr/ from 3 to 8 kcal mol/sup -1/. Both reactions, (I) and (II), are found to proceed via the formation of long-lived MFK complexes (MequivalentCs, Rb). However, a strongly different reactivity behavior is observed, attributable mainly to the difference in sign of the exoergicities of the reactions. Angular distributions of reactive (R) and nonreactive (N) scattering show characteristic bimodal structure due to the (nearly) symmetric forward--backward peaking in the center-of-mass (c.m.) system. The reactive branching fraction for each reaction has been determined at five values of E-bar/sub tr/ by analysis of the angular distributions of the reactive and nonreactive scattering. For the endoergic reaction (I) F/sub R/ is small, increasing with E-bar/sub tr/, while for the exoergic reaction (II) F/sub R/approx. =1/2, decreasing slightly with E-bar/sub tr/. The cross section for complex formation sigma/sub C/=sigma/sub R/+sigma/sub N/ is found to decline with energy, as expected on the basis of the orbiting-capture (centrifugal barrier) model. Approximate c.m. differential cross sections have been obtained by an iterative fitting procedure that satisfactorily reproduced the laboratory scattering data. A simple, uncoupled, angle-recoil velocity distribution function of the conventional 1/sintheta form (with a slightly energy-dependent oscillation) and a modified Maxwellian recoil distribution has been found to be adequate. The average relative translational energy of the scattered products, E-bar'/sub tr/, is found to increase essentially linearly with increasing E-bar/sub tr/. The theoretical implications of the present experimental results are discussed. (AIP)

• Research Organization: Chemistry and Physics Departments, The University of Texas at Austin, Texas 78712
• OSTI ID: 7238407
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 65:11; ISSN JCPSA
• 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
BEAMS
CESIUM COMPOUNDS
CESIUM FLUORIDES
CHEMICAL REACTIONS
COLLISIONS
CROSS SECTIONS
DISTRIBUTION
ELEMENTS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
METALS
MOLECULAR BEAMS
MOLECULE COLLISIONS
POTASSIUM
RUBIDIUM COMPOUNDS
RUBIDIUM FLUORIDES