TY - JOUR
T1 - Comparison of models for calculating the RRKM unimolecular rate constant k(E, J)
AU - Zhu, Ling
AU - Hase, William L.
N1 - Funding Information:
This research was supported by the National Sci-ence Foundation, The Ford Motor Corporation Scientific Research Laboratory, and the Institute for Manufacturing Research at Wayne State University. David Wardlaw and Christoph Schlier are thanked for very helpful discussions.
PY - 1990/11/30
Y1 - 1990/11/30
N2 - Both adiabatic and active treatments of the rotational quantum number K are considered in evaluating the RRKM unimolecular rate constant k(E, J). If K is treated adiabatically, k(E, J) is a weighted average of individual k(E, J, K) unimolecular rate constants. For non-variational transition states, this k(E, J) is identical to the one which results by treating K as an active degree of freedom with the proper limits placed on K. Another model for treating K as active is to let energy exchange statistically between the vibrational modes and the K-dependent term of the rotational energy. If a separable rigid rotor/harmonic oscillator model is used to calculate the sum and density of states for the transition state and reactant, respectively, the latter K active model is found to give a substantially smaller k(E, J).
AB - Both adiabatic and active treatments of the rotational quantum number K are considered in evaluating the RRKM unimolecular rate constant k(E, J). If K is treated adiabatically, k(E, J) is a weighted average of individual k(E, J, K) unimolecular rate constants. For non-variational transition states, this k(E, J) is identical to the one which results by treating K as an active degree of freedom with the proper limits placed on K. Another model for treating K as active is to let energy exchange statistically between the vibrational modes and the K-dependent term of the rotational energy. If a separable rigid rotor/harmonic oscillator model is used to calculate the sum and density of states for the transition state and reactant, respectively, the latter K active model is found to give a substantially smaller k(E, J).
UR - http://www.scopus.com/inward/record.url?scp=0001256197&partnerID=8YFLogxK
U2 - 10.1016/0009-2614(90)85528-K
DO - 10.1016/0009-2614(90)85528-K
M3 - Article
AN - SCOPUS:0001256197
SN - 0009-2614
VL - 175
SP - 117
EP - 124
JO - Chemical Physics Letters
JF - Chemical Physics Letters
IS - 1-2
ER -