CCL: IR chemiluminescence?

Some additions. I concur, additional calculations are needed, like full QM transition probabilities. I’m not sure how accurate or relevant such calculations are. In most experimental setups (except high vacuum) the energy would be dissipated by collisions. The question does come up in interstellar chemistry, you could try looking in that field for precedents. I do know that even there, they frequently consider reactions to occur on particle surfaces in interstellar clouds, but I have seen calculations of radiative energy dissipation, mostly for systems with 3-5 atoms at most. I don’t know the field, only a colleague active there (Gunnar Nyman), you could look up some of his publications for suitable starting points.






From: ":at:" [ ":at:"] On Behalf Of Brian Skinn bskinn*
Sent: den 21 oktober 2016 02:40
To: Norrby, Per-Ola <Per-Ola.Norrby ":at:">
Subject: CCL: IR chemiluminescence?




No, those data would not fall out of 'standard' QM/MM simulation, or even fully quantum MD simulations.


Both types routinely use the Born-Oppenheimer approximation, where nuclear and electronic motions are taken to be independent. The Further approximation of classical (non-quantum mechanical) motion of the nuclei is also typically introduced. This classical treatment of nuclear motion eliminates any notion of vibrational quantization that would be necessary for the simulations to naturally 'spin out' IR emission information.


Additional processing of the MD simulation results would be required to obtain such information, if it is even possible to do so.




On Thu, Oct 20, 2016 at 2:22 PM, brupalf brupalf| <owner-chemistry^^> wrote:

A general, likely naive, question from an experimentalist:  If one were to simulate a gas-phase reaction by QM/MM, the transition structure could transform into a vibrationally excited product, depending, I guess, on the reaction and the state of the reactants. I mean, that energy has to be somewhere when things roll down the hill. Experimentally, that energy is sometimes emitted from the product and detected as IR radiation. Can that emission arise as a matter of course in “standard" QM/MM simulations, or would such IR emission require separate/additional calculations? 




Bruce A. Palfey
Associate Professor of Biological Chemistry &

Associate Director, Program in Chemical Biology
Department of Biological Chemistry
University of Michigan Medical School
1150 W. Medical Center Drive
Ann Arbor, MI 48109-0606
(734) 615-2452



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