From owner-chemistry- at -ccl.net Thu Apr 17 02:21:00 2008 From: "Sue Lam chsue2004#yahoo.com" To: CCL Subject: CCL:G: UV-Vis spectra prediction Message-Id: <-36770-080417013341-22370-0oQKZhUoORWKTjEPtPAsZA]|[server.ccl.net> X-Original-From: Sue Lam Content-Transfer-Encoding: 8bit Content-Type: multipart/alternative; boundary="0-2006443586-1208406809=:8689" Date: Wed, 16 Apr 2008 21:33:29 -0700 (PDT) MIME-Version: 1.0 Sent to CCL by: Sue Lam [chsue2004|-|yahoo.com] --0-2006443586-1208406809=:8689 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Dear David Gallagher, I am also interested in that topic. Could I have a copy of your powerpoint? Thanks, Sue "David Gallagher gallagher.da{=}gmail.com" wrote: Bonjour Jerome, The band-width is related to the gradient of the excited state at the transition, i.e. a high gradient allows access to more vibrational levels > from the ground state and hence, a higher band-width, conversely a low gradient gives a narrow peak. I have some Powerpoint slides on UV-spectra that I put together a few years ago explaining the concept . Please let me know if you want a copy of them. Regards, David Gallagher CACheResearch.com At 05:16 AM 4/16/2008, Jerome Kieffer Jerome.Kieffer{=}terre-adelie.org wrote: Dear CCLers, I am trying to reproduce experimental UV-spectra of organic molecules : After the conversion wavelength (nm) -> energy (cm-1) of the experimental spectrum, I deconvoluted it by a sum of gaussian functions (using FitYK). It fits well. Transitions I obtained using TDDFT are pretty good compared with the center of the gaussian deconvolution, but the FWHM of the experimental spectrum's gaussian varies from 2000 to 8000 cm-1. So my question is: is it possible to calculate the broadening of an absorption band ? some software like gausssum suggest a FWMH of arround 3000cm-1 Thank you for your help Regards --------------------------------- Jérôme Kieffer http://www.terre-adelie.org --------------------------------- Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. --0-2006443586-1208406809=:8689 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: 8bit
Dear David Gallagher,
 
I am also interested in that topic. Could I have a copy of your powerpoint?
 
Thanks,
Sue

"David Gallagher gallagher.da{=}gmail.com" <owner-chemistry,ccl.net> wrote:
Bonjour Jerome,

The band-width is related to the gradient of the excited state at the transition, i.e. a high gradient allows access to more vibrational levels > from the ground state and hence, a higher band-width, conversely a low gradient gives a narrow peak.  I have some Powerpoint slides on UV-spectra that I put together a few years ago explaining the concept . Please let me know if you want a copy of them.

Regards,
David Gallagher
CACheResearch.com

At 05:16 AM 4/16/2008, Jerome Kieffer Jerome.Kieffer{=}terre-adelie.org wrote:
Dear CCLers,

I am trying to reproduce experimental UV-spectra of organic molecules :

After the conversion wavelength (nm) ->  energy (cm-1)  of the experimental spectrum,  I deconvoluted it by a sum of gaussian functions (using FitYK). It fits well.

Transitions I obtained using TDDFT are pretty good compared with the center of the gaussian deconvolution,  but the FWHM of the experimental spectrum's gaussian varies from 2000 to 8000 cm-1.

So my question is: is it possible to calculate the broadening of an absorption band ? some software like gausssum suggest a FWMH of arround 3000cm-1   
Thank you for your help

Regards
Jérôme Kieffer
http://www.terre-adelie.org

Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. --0-2006443586-1208406809=:8689--