State resolved rotational excitation in D/sub 2/+H/sub 2/ collisions
In a crossed molecular beam experiment time-of-flight distributions of ortho D/sub 2/ molecules scattered from normal H/sub 2/ (nH/sub 2/) and para H/sub 2/ (pH/sub 2/) have been measured in a center-of-mass angular range of 75/sup 0/ to 180/sup 0/. The collision energies were 84.1 and 87.2 meV, respectively. In all spectra the rotational excitation of D/sub 2/ from j = 0 to j = 2 has been resolved. With pH/sub 2/ as secondary beam the same transition could also be observed for H/sub 2/. The measurements show that the probability for rotational excitation of D/sub 2/ depends on whether the scattering partner H/sub 2/ is rotating (nH/sub 2/) or not (pH/sub 2/). In the first case the cross sections are larger by a factor of approximately 2. The reason for this behavior is the presence of an additional interaction term which is at long range distances, identical to the quadrupole--quadrupole interaction and which is absent if H/sub 2/ is in the j = 0 state. The experimentally derived differential cross sections for the rotational excitation of D/sub 2/ and H/sub 2/ are compared with theoretical results obtained by close coupling calculations based on the ab initio potential surface of Meyer and Schaefer. The comparison shows a remarkable agreement. However, small deviations in the positions of the diffraction oscillations of the elastic differential cross section curve suggest that the isotropic potential term has to be shifted to smaller distances. In order to maintain the relative position of the inelastic differential cross section curves which are well predicted by the ab initio potential the same shift has to be applied to the anisotropic potential terms.
- Research Organization:
- Max-Planck-Institut fuer Stroemungsforschung, D 3400 Goettingen, Federal Republic of Germany
- OSTI ID:
- 5502863
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 78:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DEUTERIUM
MOLECULE-MOLECULE COLLISIONS
HYDROGEN
ANGULAR DISTRIBUTION
COLLIDING BEAMS
DIFFERENTIAL CROSS SECTIONS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXPERIMENTAL DATA
ROTATIONAL STATES
SCATTERING
BEAMS
COLLISIONS
CROSS SECTIONS
DATA
DISTRIBUTION
ELEMENTS
ENERGY LEVELS
EXCITED STATES
HYDROGEN ISOTOPES
INFORMATION
ISOTOPES
LIGHT NUCLEI
MOLECULE COLLISIONS
NONMETALS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
STABLE ISOTOPES
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena