CCL: Pressure dependence in reaction rate kinetics calculations

 Sent to CCL by: "Ted  Dibble" [tsdibble{:}]
 The answers to your questions can be found in most textbooks.  Start with a
 physical chemistry textbook for the basics, and look in a graduate kinetics
 textbook for fuller explanations.  Look for the Lindeman or Lindeman-Hinshelwood
    The three-body reaction is the net reaction including the third body, e.g.:
        ClO + NO2 + M  =  ClONO2 + M
 where M is the third body, and [M] corresponds to the total concentration of
 gas phase species.  This is in contrast to the elementary reactions:
       ClO + NO2  ->  ClONO2*
       ClONO2*   ->  ClO + NO2
       ClONO2*  + M   ->  ClONO2  + M
 Please note:  TST applies where there is a Boltzmann distribution of energy,
 which corresponds to the high-pressure limit rather than the low-pressure
    To calculate rate constants versus pressure, see the UNIMOL package, made
 available at
 Good luck!
 Theodore S. Dibble
 Chemistry Department
 SUNY-Environmental Science and Forestry
 1 Forestry Drive
 Syracuse, NY 13210
 (315) 470-6596
 (315) 470-6856  (fax)
 > "RD Miles rdmsgl!A!"  wrote:
 > Sent to CCL by: RD Miles [rdmsgl^]
 > --0015173fe52af75fe4049efe5381
 > Content-Type: text/plain; charset=ISO-8859-1
 > I have been working on calculating reaction rate constants at the low
 > pressure limit using TST type methodologies. However, I need to understand
 > how to transition into calculations for high pressure systems.
 > Could you recommend any references that deal specifically with the pressure
 > dependence of reaction rate constants, and how it is addressed in
 > computational chemistry?
 > Questions I have are:
 >    - Can TST based methods be adapted to high pressure systems?
 >    - What is meant by "3 body reactions" in many kinetics
 >    - What is meant by the pressure dependence "fall-off" in some
 >    rate constant descriptions?
 > Any help on this subject would be greatly appreciated.
 > -RD