Accession Number : ADA325618

Title :   Large Amplitude Motions in Polyatomic Molecule Spectra: Intramolecular Vibrational Redistribution and Isomerization.

Descriptive Note : Final rept. 1 Dec 93-30 Nov 96,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY

Personal Author(s) : Field, Robert W. ; Silbey, Robert J.

PDF Url : ADA325618

Report Date : 18 FEB 1997

Pagination or Media Count : 16

Abstract : Through Stimulated Emission Pumping (SEP) studies of highly excited vibrational levels of the electronic ground state of HCP, the spectroscopic signatures of bond breaking isomer/atom (HCP right arrow HPC) were detected and interpreted for the first time. Two novel spectroscopic schemes, UV excited-IR detected fluorescence excitation spectroscopy and UV excited-Auger detected Laser Excited Metastable (LEM) spectroscopy, prove the existence of a Gateway Mediated Intersystem Crossing (GMISC) mechanism in acetylene. In GMISC, one spectral vibronic state couples the single bright state to a dense manifold of dark states. The complementarity of LEM and Laser Induced Fluorescence (LIF) spectroscopy was found to be ideally suited for study of ISC because LEM is blind to short live radiating states and LIF is blind to metastable states, a pattern recognition technique. Extended Cross Correlation (XCC), which is capable of picking out multiple patterns that are repeated in multiple spectra without any prior knowledge of the forms of the patterns, was applied with extraordinary success to several types of spectra. Among these was a data set consisting of electron beam excited infrared spectra of CO, recorded by Dr. Stephen Lipson and colleagues at the Air Force Phillips Laboratory. All of the severely overlapped features were "unzipped" assigned, and independently represented by time dependent populations. The central theme in each of these projects is the development of experimental methods, theoretical models, and pattern-recognition schemes capable of extracting previously inaccessible information from spectra of highly excited molecules.

Descriptors :   *MOLECULAR VIBRATION, *ELECTRONIC STATES, *BONDING, *ACETYLENE, *ISOMERIZATION, EMISSION, SPECTROSCOPY, POLYATOMIC MOLECULES, LASER INDUCED FLUORESCENCE, EXCITATION, HIGH DENSITY, SIGNATURES, PATTERN RECOGNITION, GROUND STATE, CARBON MONOXIDE, POTENTIAL ENERGY, METASTABLE STATE.

Subject Categories : Physical Chemistry
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE