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

Journal Article · Wed Feb 01 00:00:00 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), Vol. 90:3
• Country of Publication: United States
• Language: English

Related Subjects

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