From owner-chemistry@ccl.net Thu Nov 27 07:56:00 2008 From: "willsd ~ appstate.edu" To: CCL Subject: CCL:G: Confusing issue of Raman intensity Vs Static polarizability Message-Id: <-38188-081127073155-32286-54DO3jncuE1sLWiNpsv0mg##server.ccl.net> X-Original-From: Content-Disposition: inline Content-Language: en Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Date: Thu, 27 Nov 2008 12:31:33 GMT MIME-Version: 1.0 Sent to CCL by: [willsd_+_appstate.edu] If the problem here is an attempt to compare theoretical calculations with measured Raman spectra, there are (in addition to the things described here) two more issues. 1: The measured Raman (conventional, NOT resonance Raman nor SERS) spectrum will depend on the type of light detection in the spectrometer. The equations that connect measured intensity with computed activity are different for photon counting versus power detection. 2: The experimental spectrum also depends quite strongly on the wavelength dependent response of the spectrometer. This can only be accounted for by careful calibration of the entire spectrometer. This requires measuring the spectrum of a light source whose emission spectrum is known; this is usually a blackbody source at a known temperature. There is a recent paper by Williams, Johnson, Kitchens, and Gibbons (in TCA) that describes these issues and reviews some of the literature on the subject. The paper also makes some specific recommendations about using Raman activities, computed by Gaussian, from different theoretical models, HF, several DFT methods, and MP2. The main conclusion was that basis set is probably more important than level of theory, and that CH (and very likely other XH) stretching vibrations are likely to be poorly computed due to their strongly anharmonic nature. Steve Williams ----- Original Message ----- > From: "Vasile Chis vchis[A]phys.ubbcluj.ro" Date: Thursday, November 27, 2008 6:57 am Subject: CCL:G: Confusing issue of Raman intensity Vs Static polarizability To: "Williams, Steve " > Dear Mi Yang, > > > A relationship that can be used for converting calculated Raman > activities to Raman intensities can be found, for instance, in: > > P.L. Polavaru, J. Phys. Chem. 94 (1990) 8106 > > V. Krishnakumar, G. Keresztury, T. Sundius, R. Ramasamy, J. Mol. > Struct. 702 > (2004) 9. > > > > If Freq(Raman) is specified in the route section of Gaussian, Raman > activities of normal modes and not Raman intensities are > calculated. Raman > intensities depend on the exciting laser wave number and on the > Boltzmannpopulation of the vibrational levels. > > > > Hope this helps! > > > > Best regards, > > Vasile Chis > > **========================= > Prof.dr. Vasile Chis > Babes-Bolyai University > Faculty of Physics > Kogalniceanu 1 > RO-400084 Cluj-Napoca > Romania > Tel: +40264405300 > Fax: +40591906 > vchis-x-phys.ubbcluj.ro > vasilechis-x-gmail.com > www.phys.ubbcluj.ro/~vchis > ======================== > > > On Thu, Nov 27, 2008 at 11:46 AM, Mi Yang miyang3790*gmail.com < > owner-chemistry-x-ccl.net> wrote: > > > > > Sent to CCL by: "Mi Yang" [miyang3790~~gmail.com] > > Dear Kzys!! > > > > Yes I am a gaussian03 Rev user but Your comments a bit confusing > for me as > > in G03 manual it is clearly mentioned that by using Freq=Raman > you can > > "Compute Raman intensities in addition to IR intensities" so I am > not> understanding ur point of view. > > > > http://www.gaussian.com/g_ur/k_freq.htm > > > > There are some good quality of publications where they show > computed raman > > intensities with gaussian e.g. > > J. AM. CHEM. SOC. 2005, 127, 10977-10981.pdf > > > > > > > http://homepage.univie.ac.at/Ferenc.Simon/publications/2005/Schaman_KBproc2005.pdf> > > So I have stoped my work and first want to confirm it. > > > > Secondly, my calculated Freq value of Raman spectrum is in good > agreement> to the experimental value for specific mode of > vibrations after scaling. I > > am not comparing directlt intensity with intensity.My purpose is > to show > > increase of intensity or activity upon intercalation of metal > atom.What do > > you think in this regard? > > > > I need your comments in detail especially in view of above > references> > > > > > "zborowsk]|[chemia.uj.edu.pl" wrote: > > > > > > Sent to CCL by: zborowsk**chemia.uj.edu.pl > > > > > > > > > > > Sent to CCL by: favaro [laurent.favaro[#]u-psud.fr] > > > > Do you mean that G03 does not calculate Raman Cross-section ? > > > > I believe you are wrong. > > > > > > Gaussian calculates Raman Activities, not Raman Intensities, and > > obviously > > > it is not the same. Raman Activities cannot be compared > directly with > > > experimental Raman spectra. > > > > > > Regards > > > > > > Kzys > > > > > > > Regards. > > > > LF > > > > > > > > zborowsk]*[chemia.uj.edu.pl a crit : > > > >> Sent to CCL by: zborowsk|,|chemia.uj.edu.pl > > > >> Hi > > > >> Dear Mi Yang > > > >> I want to warn you if you are Gaussian user. > > > >> Gaussian does not calculate Raman Intensities > > > >> > > > >> > > > >> > > > >> Sent to CCL by: favaro [laurent.favaro|*|u-psud.fr] > > > >> Raman intensity is related to the square > > > >> of the derivative of polarizability with respect > > > >> to the normal coordinates of the vibrationnal mode. > > > >> Best regards, > > > >> Dr Favaro > > > >> Mi Yang miyang3790_+_gmail.com a crit : > > > >> > > > >> Sent to CCL by: "Mi Yang" [miyang3790*gmail.com] > > > >> Dear CCL users, > > > >> I need some comments or refs about my problem. I am > studying the > > > >> interaction of a metal with a boron cluster. I found the large > > increase > > > >> of static polarizability and hyperpolarizability upon > interaction of > > > >> metal atom to that boron cluster. I also calculated the > Raman spectrum > > > >> which also showed high increase of intensity in metal boron > cluster. I > > > >> read some indirect relationship b/m these two properties but > now in > > > >> spite > > > >> of my best efforts I could not find the direct relationship > between> > >> Static polarizability and Raman intensity. Anybody > who knows any ref > > or > > > >> comments about this relationship (Static > > > >> polarizability/hyperpolarizability and Raman intensity) > would be > > highly > > > >> appreciated.? > > > >> Miyang > > > >> P.R.China> > > > > > > > > > > > > > > > > > -- > > > Krzysztof Zborowski > > > Faculty of Chemistry > > > Jagiellonian University > > > 3 Ingardena Street > > > 30-060 Krakow > > > Poland > > > phone: +48(12)632-4888 ext. 2064 or 2067 > > > fax: +48(12)634-05-15 > > > email: zborowsk###chemia.uj.edu.pl > > > gg 3817259 > > > skype kzys70 > > > www.chemia.uj.edu.pl/~zborowsk> > > > > > > -- > > This message has been scanned for viruses and > > dangerous content by MailScanner, and is > > believed to be clean. > > > > >