Hindered internal rotation and ortho-H/sub 2/ enrichment in trans-stilbene--H/sub 2//D/sub 2/ complexes

Journal Article · Wed Feb 01 04:00:00 EST 1989 · J. Chem. Phys.; (United States)

OSTI ID:6549004

DeHaan, D O; Zwier, T S

A supersonic free jet expansion has been used to prepare trans-stilbene--H/sub 2/ and D/sub 2/ complexes. The cooling in the jet collapses most of the ortho and para H/sub 2/ and D/sub 2/ rotational population to the lowest rotational levels of a given nuclear spin symmetry: j = 0 and j = 1. The laser-induced fluorescence excitation spectrum of stilbene--D/sub 2/ shows a well-resolved doublet at the origin due to stilbene--D/sub 2/( j = 0) and stilbene--D/sub 2/( j = 1) complexes. The 4.9 cm/sup -1/ splitting of these transitions indicates that the D/sub 2/ molecule is undergoing hindered internal rotation in the complex and that the barrier to internal rotation changes upon electronic excitation. The relative intensities of the stilbene--D/sub 2/( j = 0) and stilbene--D/sub 2/( j = 1) origins depend on the D/sub 2/ concentration in the jet. At low D/sub 2/ flows the transitions arising from stilbene--D/sub 2/( j = 1) are favored while at high D/sub 2/ flows the ( j = 0)/(j = 1) transition intensities approach the 2:1 intensity ratio given by their nuclear spin statistical weights. By contrast, in stilbene--H/sub 2/ we observe only a single transition at the origin which we assign to stilbene--H/sub 2/( j = 1). We are able to place an upper bound on the stilbene--H/sub 2/( j = 0) transition intensity of 5% of the stilbene--H/sub 2/( j = 1) intensity. Dispersed fluorescence spectra are used to bracket the binding energies of the stilbene--H/sub 2//D/sub 2/ complexes in both ground and excited states.

• Research Organization: Department of Chemistry, Calvin College, Grand Rapids, Michigan 49506
• OSTI ID: 6549004
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 90:3; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400202* -- Isotope Effects
Isotope Exchange
& Isotope Separation
ADDUCTS
AROMATICS
COMPLEXES
DEUTERIUM
ENRICHMENT
FLUORESCENCE
HYDROCARBONS
HYDROGEN COMPLEXES
HYDROGEN ISOTOPES
ISOMERS
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
LUMINESCENCE
MOTION
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ROTATION
STABLE ISOTOPES
STILBENE