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

Abstract

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 wemore » 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.« less

Authors:
;
Publication Date:
Research Org.:
Department of Chemistry, Calvin College, Grand Rapids, Michigan 49506
OSTI Identifier:
6549004
Resource Type:
Journal Article
Journal Name:
J. Chem. Phys.; (United States)
Additional Journal Information:
Journal Volume: 90:3
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

DeHaan, D O, and Zwier, T S. Hindered internal rotation and ortho-H/sub 2/ enrichment in trans-stilbene--H/sub 2//D/sub 2/ complexes. United States: N. p., 1989. Web.
DeHaan, D O, & Zwier, T S. Hindered internal rotation and ortho-H/sub 2/ enrichment in trans-stilbene--H/sub 2//D/sub 2/ complexes. United States.
DeHaan, D O, and Zwier, T S. 1989. "Hindered internal rotation and ortho-H/sub 2/ enrichment in trans-stilbene--H/sub 2//D/sub 2/ complexes". United States.
@article{osti_6549004,
title = {Hindered internal rotation and ortho-H/sub 2/ enrichment in trans-stilbene--H/sub 2//D/sub 2/ complexes},
author = {DeHaan, D O and Zwier, T S},
abstractNote = {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.},
doi = {},
url = {https://www.osti.gov/biblio/6549004}, journal = {J. Chem. Phys.; (United States)},
number = ,
volume = 90:3,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 1989},
month = {Wed Feb 01 00:00:00 EST 1989}
}