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Title:Mass selective investigations of ultrafast dynamical processes and spectroscopy
Author(s):Wright, Scott Andrew
Doctoral Committee Chair(s):McDonald, J. Douglas
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Physical
Physics, Molecular
Abstract:Chemical systems containing heavy halogen atoms are explored by Resonantly-Enhanced Multiphoton Ionization (REMPI) with Time-of-Flight mass spectrometric (TOFMS) detection.
The multiphoton spectrum of hydrogen iodide Rydberg states is investigated. A (2+1) REMPI excitation mechanism provides access to electronic states in the region 64,641-71,352 cm$\sp{-1}$. Two-photon selection rules allow the observation of transitions forbidden in the HI absorption experiments. Many of the assigned Rydberg states contain underlying, unassigned structure with anomalous intensity fluctuations and apparent breaking off of branches. Additionally, we observe autoionized levels, most likely accessed by either a (3+1) or a direct four-photon excitation. Molecular constants are calculated for all HI bands observed. Also included is the first REMPI study of iodine atoms coming from photolyzed HI precursor.
A time-resolved study of the interaction of Br with I$\sb2$ is presented. Ultrashort laser pulses provide time resolve. The bimolecular encounter is photoinitiated from a van der Waals dimer. Results show that the photoinitiated interaction begins exclusively on the spin-orbit excited reaction surface (Br($\rm\sp2P\sb{1/2})$ + I$\sb2$), from which the complex internally converts to the ground state, transferring energy into the I$\sb2$ rovibrational degrees of freedom. Finally, the complex exits in the Br($\rm\sp2P\sb{3/2})$ + I$\sb2$(v$\sp\prime)$ channel. It seems that this non-reactive channel dominates over reactive channels (which produce I + IBr). The internal conversion time is around 45 picoseconds.
Issue Date:1994
Rights Information:Copyright 1994 Wright, Scott Andrew
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9503355
OCLC Identifier:(UMI)AAI9503355

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