University of Illinois Urbana-Champaign

Which way did it go? Revisiting the time-resolved study of bromine atom and iodine molecule

Tuchler, Matthew Frederick

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Description

Title
Which way did it go? Revisiting the time-resolved study of bromine atom and iodine molecule
Author(s)
Tuchler, Matthew Frederick
Issue Date
1995
Doctoral Committee Chair(s)
McDonald, J. Douglas
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Physical
Language
eng
Abstract
  • The low collision energy interaction of Br($\rm\sp 2P\sb {3/2}$) (Br) or Br($\rm\sp 2P\sb {1/2}$)(Br$\sp {*}$) and I$\sb 2$ is studied in real time. The method of detection, Resonance Enhanced Multiphoton Ionization (REMPI)-Time of Flight Mass Spectroscopy (TOFMS), allows unambiguous identification of products. The interaction is initiated in a restricted region of phase space defined by the geometry of the precursor dimer, H(D)Br$\rm\sp {*}I\sb 2$. The photodissociation of H(D)Br provides both Br and Br$\sp {*}$. The combination of low collision energy and narrow distribution of initial conditions results in a metastable intermediate complex, $\rm I\sb 2Br\sp {*}$. We simultaneously detect two transients, one of which is consistent with the above mentioned complex undergoing an internal conversion to either the ground or 1$\rm\sp {st}$ excited state. The second transient may contain a contribution from the ground state reaction, Br+I$\sb 2$, but interference from other channels makes this transient difficult to assign. Both transients' risetimes vary as a function of precursor constitution, i.e. H(D)Br$\rm\sp {*}I\sb 2$, a feature that is readily explained by a simple 1$\rm\sp {st}$ order kinetic model.
  • An estimate of the precursor structure is provided and used as a starting point for a series of trajectory calculations run on standard LEPS surfaces. The trajectory calculations were used to study the process initiated on the spin-orbit excited (SO) surface, Br$\sp {*}$+I$\sb 2$. At various times during the evolution on the SO surface, the trajectory is allowed to internally convert to a lower electronic surface. The trajectory is followed to completion, at which point a thorough analysis of the products is conducted. The results of these trajectory studies are presented and discussed in detail, including a prediction that the method of detection may result in a signal arising from more than one dynamic feature of the complex evolution.
Type of Resource
text
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http://hdl.handle.net/2142/22275
Copyright and License Information
Copyright 1995 Tuchler, Matthew Frederick

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