OBSERVATION OF THE """ISOMERIZATION""" STATES OF HCP: """ISOMERIZATION""" STATE VS. """NORMAL-MODE-TYPE""" STATE
Loading...
Date
1997
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
Among various kinds of bond-breaking isomerization reactions, the isomerization of a triatomic monohydride, HAB, is the simplest one: $HAB \longleftrightarrow ABH$. This system is most fundamental for both experimental and theoretical studies. On the basis of a time-{independent} picture, the isomerization process can be characterized by analysis of rotation-vibration eigenstates in the high energy region. In this study, highly excited vibrational states of HCP $\tilde{X}^{1}\Sigma^{+}$ were investigated by dispersed fluorescence and stimulated emission pumping spectroscopies. As a result, two distinct families of vibrational states were observed in the $13400-17500 cm^{-1}$ energy $region.^{h}$ One of them is well characterized by poly ads involving the bending $(\nu_{2})$ and CP stretching $(\nu_{3})$ vibrations. This 1:2 polyad structure is very robust and valid in the lower energy region. This family can be referred to as ``normal-mode-type” states. On the other hand, vibrational levels of the other family appear suddenly at $13400 cm^{-1}$. The rotational constants of these levels are much larger than those of the ``normal-mode-type” states. Moreover, these level exhibit strong anhamonicity. We have assigned this family of vibrational levels as deocalized ``isomerization” states whose existence whose predicted by a recent theoretical study. This assignment is based on the good agreement between the present spectroscopic observations and the theoretical predictions. Thus ``isomerization” states have been identified experimentally for the first time.
Description
$^{h}$ H. Ishikawa et al., J. Chem. Phys. \textbf{106}, 2980 (1997). $^{i}$ S.C.Farantos et al. J. Chem. Phys. \textbf{104}, 10055 (1996).
Author Institution: Department of Chemistry, Graduate School of Science, Tohoku University; Department of Chemistry, Massachusetts Institute of Technology
Author Institution: Department of Chemistry, Graduate School of Science, Tohoku University; Department of Chemistry, Massachusetts Institute of Technology