VERTICAL AND ADIABATIC IONIZATION ENERGY--REPLIES;THANKS

From: "E. Lewars" <elewars # - at - # alchemy.chem.utoronto.ca>
Subject: VERTICAL AND ADIABATIC IONIZATION ENERGY--REPLIES;THANKS
Date: Mon, 19 Jul 1999 11:29:49 -0400 (EDT)
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" <elewars # - at - # alchemy.chem.utoronto.ca>
 Subject: Re: CCL:VERTICAL & ADIABATIC IONIZATION POT
 Message-ID: <Pine.SOL.3.95.990712105553.13088D-100000 # - at - #
 arnold.chem.uoa.gr>
 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" <elewars # - at - # alchemy.chem.utoronto.ca>
 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" <elewars # - at - # alchemy.chem.utoronto.ca>
 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" <elewars # - at - # alchemy.chem.utoronto.ca>
 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/
 ----------------------------------------------