From chemistry-request: at :server.ccl.net Mon Jul 19 11:37:47 1999 Received: from alchemy.chem.utoronto.ca (alchemy.chem.utoronto.ca [142.150.224.224]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id LAA22256 for ; Mon, 19 Jul 1999 11:37:46 -0400 Received: (from elewars%!at!%localhost) by alchemy.chem.utoronto.ca (8.9.3/8.9.3) id LAA07586 for chemistry*- at -*ccl.net; Mon, 19 Jul 1999 11:29:49 -0400 (EDT) Date: Mon, 19 Jul 1999 11:29:49 -0400 (EDT) From: "E. Lewars" Message-Id: <199907191529.LAA07586&$at$&alchemy.chem.utoronto.ca> To: chemistry.,at,.ccl.net Subject: VERTICAL AND ADIABATIC IONIZATION ENERGY--REPLIES;THANKS 1999 July 19 REPLIES TO QUESTION ABOUT VERTICAL AND ADIABATIC IONIZATION POTENTIALS Hello, Here are the responses to my question. I wish to thank all who responded. There is plenty of info' on IPs and EAs (reply #2, 4 ), but it not always stated explicitly if the measured quantity is a vertical or adiabatic energy. I gather that the data normally published are for adiabatic IPs and EAs. It seems that if you want vertical quantities you have to ferret them out of the literature. E. Lewars -------------------- THE QUESTION: 1999 July 11 SOME IONIZATION POTENTIALS (AND IF POSSIBLE ELECTRON AFFINITIES) Hello, Has anyone *experimental* values (with references) for vertical _and_ adiabatic ionization potentials of a few molecules: molecule A: vert IP adiabatic IP molecule B: vert IP adiabatic IP molecule C: vert IP adiabatic IP I'm looking for the IPs (ionization energies; the minimum E needed to ionize the molecule) of fairly small molecules, say 2--8 heavy (non-H) atoms. (If the same info is also available on the _electron affinities_ of a few molecules, I would appreciate receiving this too). Thanks, E. Lewars ========================== THE REPLIES: #1 Date: Mon, 12 Jul 1999 10:58:04 +0300 (EET DST) To: "E. Lewars" Subject: Re: CCL:VERTICAL & ADIABATIC IONIZATION POT Message-ID: Dear Dr. Lewars, I would appreciate if you summarized for the group any responses you may receive. This is very interesting data. Regards, John Kerkines Athens, Grece ========== #2 N 3 Jul 12 Karl Irikura (94) Re: CCL:VERTICAL & ADIABATIC IONIZACommand: Read MessageMessage 3/6 from Karl Irikura Jul 12 '99 at 9:16 am X-Sender: irikura[ AT ]mailserver3.nist.gov Date: Mon, 12 Jul 1999 09:16:26 -0400 To: "E. Lewars" Subject: Re: CCL:VERTICAL & ADIABATIC IONIZATION POT Mime-Version: 1.0 Dear Dr. Lewars, I'm not aware of any complilations of vertical IPs. But many adiabatic values are available online from the NIST WebBook: http://webbook.nist.gov/ It includes many references. If you check those that involve measured photoelectron spectra, the original papers may contain vertical IPs, either tabulated or in the experimental spectra. Many adiabatic EAs are also compiled in the WebBook, and the corresponding references to PES experiments may provide vertical detachment energies (viz., at the geometry of the anion). But I'm not sure how one could easily measure vertical electron affinities (viz., at the geometry of the neutral molecule). The only way I can think of would be to have a complete vibrational assignment of the anion photoelectron spectrum and find the most intense peak that has as its upper state the vibrational ground state of the neutral. Please let me know if you learn of a better way! Sincerely, Karl Irikura ---------------------------------------------- Dr. Karl K. Irikura National Institute of Standards and Technology 100 Bureau Drive, Stop 8380 Gaithersburg, MD 20899-8380 voice: 301-975-2510 fax: 301-869-4020 e-mail: karl.irikura[ AT ]nist.gov http://www.nist.gov/compchem/ ---------------------------------------------- #3 N 4 Jul 12 Matthew F Schlecht (69) Re: CCL:VERTICAL & ADIABATIC IONIZACommand: Read MessageMessage 4/6 from Matthew F Schlecht Jul 12 '99 at 2:00 pm X-Lotus-FromDomain: DUPONT- at -DUPONT_MHUB To: "E. Lewars" Date: Mon, 12 Jul 1999 14:00:24 -0400 Subject: Re: CCL:VERTICAL & ADIABATIC IONIZATION POT Prof. Lewars, I would be very interested in seeing the responses to your question. I'm assuming that you are exploring ways to model these properties computationally, and if you are willing I'd be very interested in hearing more about that as well. I hope you will post your usual informative summary to the CCL. Matthew Schlecht DuPont Ag [Thanks. Yes, I want to calculate a few IPs and EAs by different methods and to compare the results with experiment and with Koopmans theorem predictions. E. Lewars ] ============ #4 Jul 19 Karl Irikura (161) Re: IONIZATION ECommand: Read MessageMessage 4/4 from Karl Irikura To: "E. Lewars" Subject: Re: IONIZATION E Dear Dr. Lewars, There is no difference between the terms "ionization potential" (IP) and "ionization energy" (IE). Yes, the usual default is for values to be adiabatic, since these are the thermodynamically relevant quantities, such as measured by mass spectrometry. Vertical quantities are usually accessible only using spectroscopic methods, which are governed by Franck-Condon factors. As a result, adiabatic values are always <= vertical values for endoergic quantities (such as IEs and electron detachment energies), and are always >= vertical values for exoergic quantities (such as electron affinities). (This may be clearer if you draw a diagram for a diatomic molecule.) If you will work with ion thermochemistry, I recommend reading the introduction to the GIANT tables for a reasonably brief review of the techniques and pitfalls (esp. different thermodynamic conventions): Lias, S. G.; Bartmess, J. E.; Liebman, J. F.; Holmes, J. L.; Levin, R. D.; Mallard, W. G. J. Phys. Chem. Ref. Data 1988, 17, Suppl. 1. Similar material appears to be online at http://webbook.nist.gov/chemistry/ion/ (but I haven't read this). Best wishes! Karl I. At 09:30 PM 7/17/99 -0400, you wrote: >1999 July 17 >Hello, > >Thank you for the information about ionization potentials on the NIST >website. I gather from your email letter that ionization potential/energy >(what is the difference between IP and IE anyway?) means _adiabatic_ >unless >vertical is specifically stated. I thought that IP was sometimes >measured by mass spectrometry (the appearance potential, the minimum energy of >electrons needed to ionize the molecule), and that in that case the ion was >formed with the geometry of the neutral, giving the vertical IP. >And it seems that for electron affinities, even more than for IPs, the >standard measured values are adiabatic. No, I can't think of any other way to get vertical EAs. >It just occurs to me I'd better reread Chapter 10 in the book edited >by you and Frurip, especially the refs for p. 192. > >Thanks for your help > > E. Lewars >======================= ---------------------------------------------- Dr. Karl K. Irikura National Institute of Standards and Technology 100 Bureau Drive, Stop 8380 Gaithersburg, MD 20899-8380 voice: 301-975-2510 fax: 301-869-4020 e-mail: karl.irikura-: at :-nist.gov http://www.nist.gov/compchem/ ----------------------------------------------