FOURTH-ORDER VIBRATIONAL TRANSITION STATE THEORY AND CHEMICAL KINETICS

Stanton, John F.

Permalink

https://hdl.handle.net/2142/79399 Copy

Description

Title

FOURTH-ORDER VIBRATIONAL TRANSITION STATE THEORY AND CHEMICAL KINETICS

Author(s)

Stanton, John F.

Contributor(s)

• Gong, Justin Z
• Matthews, Devin A.

Issue Date

23-Jun-15

Keyword(s)

Dynamics/Kinetics/Ultrafast

Abstract

Second-order vibrational perturbation theory (VPT2) is an enormously successful and well-established theory for treating anharmonic effects on the vibrational levels of semi-rigid molecules. Partially as a consequence of the fact that the theory is exact for the Morse potential (which provides an appropriate qualitative model for stretching anharmonicity), VPT2 calculations for such systems with appropriate {it ab initio} potential functions tend to give fundamental and overtone levels that fall within a handful of wavenumbers of experimentally measured positions. As a consequence, the next non-vanishing level of perturbation theory -- VPT4 -- offers only slight improvements over VPT2 and is not practical for most calculations since it requires information about force constants up through sextic. However, VPT4 (as well as VPT2) can be used for other applications such as the next vibrational correction to rotational constants (the ``gammas'') and other spectroscopic parameters. In addition, the marriage of VPT with the semi-classical transition state theory of Miller (SCTST) has recently proven to be a powerful and accurate treatment for chemical kinetics. In this talk, VPT4-based SCTST tunneling probabilities and cumulative reaction probabilities are give for the first time for selected low-dimensional model systems. The prospects for VPT4, both practical and intrinsic, will also be discussed.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/79399

Owning Collections