[MOS] September 26, 2006

[Zina Queen]

Seminar on
Modern Optics and Spectroscopy


Art Utz, Tufts University

Probing methane dissociation dynamics with selectively energized reagents

September 26, 2006

12:00 noon - 1:00 p.m.

Abstract:

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?
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.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.mit.edu/pipermail/mos/attachments/20060925/40a45644/attachment.htm