<!doctype html public "-//W3C//DTD W3 HTML//EN">
<html><head><style type="text/css"><!--
blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 }
--></style><title>September 26, 2006</title></head><body>
<div><font face="Arial" size="+1" color="#000000">Seminar on<br>
<b>Modern Optics and Spectroscopy<br>
<br>
<br>
Art Utz</b>, Tufts University<br>
<br>
<i><b>Probing methane dissociation dynamics with selectively energized
reagents<br>
<br>
</b></i>September 26, 2006<br>
<br>
12:00 noon - 1:00 p.m.<br>
<br>
</font><font face="Times New Roman" size="+1"
color="#000000"><b>Abstract:</b></font><br>
<font face="Times New Roman" size="+1"
color="#000000"><b></b></font></div>
<div><font face="Arial" size="+1" color="#000000">The mechanism for
methane activation on nickel is well studied, but the presence of many
thermally excited vibrational and rotational states in reactive
samples can obscure the detailed energetics of this important
process. We combine state-resolved infrared laser excitation
with beam-surface scattering measurements to quantify the reactivity
of methane in single rotational and vibrational quantum states.
Our data address several important questions regarding the dynamics
and mechanism for methane's dissociation on a clean nickel surface:
1) How effectively does energy deposited into select energetic
coordinates promote dissociation? 2) How important is vibrational
excitation at promoting reaction? 3) Does energy flow freely and
rapidly among energetic degrees of freedom on the time scale of
reaction, or is activation non-statistical or vibrational
mode-specific? 4) Which nuclear motions are most effective at moving
the reactive system through the transition state region?</font></div>
<div><font face="Arial" size="+1" color="#000000">We find that C-H
stretching excitation can be significantly more effective than
translational energy in promoting dissociation, and we observe
vibrational mode specific reactivity in which the ability of
vibrational energy to promote reaction varies markedly with the
vibrational character of the excited state. These observations
shed light on the extent of vibrational energy flow that occurs during
reaction.</font></div>
</body>
</html>