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Title: Zero-point energy, tunneling, and vibrational adiabaticity in the Mu + H2 reaction

Abstract

Abstract: Isotopic substitution of muonium for hydrogen provides an unparalleled opportunity to deepen our understanding of quantum mass effects on chemical reactions. A recent topical review [Aldegunde et al., Mol. Phys. 111, 3169 (2013)] of the thermal and vibrationally-stateselected reaction of Mu with H2 raises a number of issues that are addressed here. We show that some earlier quantum mechanical calculations of the Mu + H2 reaction, which are highlighted in this review and which have been used to benchmark approximate methods, are in error by as much as 19% in the low-temperature limit. We demonstrate that an approximate treatment of the Born–Oppenheimer diagonal correction that was used in some recent studies is not valid for treating the vibrationally-state-selected reaction. We also discuss why vibrationally adiabatic potentials that neglect bend zero-point energy are not a useful analytical tool for understanding reaction rates and why vibrationally nonadiabatic transitions cannot be understood by considering tunneling through vibrationally adiabatic potentials. Finally, we present calculations on a hierarchical family of potential energy surfaces to assess the sensitivity of rate constants to the quality of the potential surface.

Authors:
; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1167594
Report Number(s):
PNNL-SA-101788
KC0301020
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Molecular Physics, 113(2):160-175
Country of Publication:
United States
Language:
English
Subject:
Born–Oppenheimer diagonal correction, kinetic isotope effects, tunneling, quantum

Citation Formats

Mielke, Steven L., Garrett, Bruce C., Fleming, Donald G., and Truhlar, Donald G. Zero-point energy, tunneling, and vibrational adiabaticity in the Mu + H2 reaction. United States: N. p., 2015. Web. doi:10.1080/00268976.2014.951416.
Mielke, Steven L., Garrett, Bruce C., Fleming, Donald G., & Truhlar, Donald G. Zero-point energy, tunneling, and vibrational adiabaticity in the Mu + H2 reaction. United States. doi:10.1080/00268976.2014.951416.
Mielke, Steven L., Garrett, Bruce C., Fleming, Donald G., and Truhlar, Donald G. Fri . "Zero-point energy, tunneling, and vibrational adiabaticity in the Mu + H2 reaction". United States. doi:10.1080/00268976.2014.951416.
@article{osti_1167594,
title = {Zero-point energy, tunneling, and vibrational adiabaticity in the Mu + H2 reaction},
author = {Mielke, Steven L. and Garrett, Bruce C. and Fleming, Donald G. and Truhlar, Donald G.},
abstractNote = {Abstract: Isotopic substitution of muonium for hydrogen provides an unparalleled opportunity to deepen our understanding of quantum mass effects on chemical reactions. A recent topical review [Aldegunde et al., Mol. Phys. 111, 3169 (2013)] of the thermal and vibrationally-stateselected reaction of Mu with H2 raises a number of issues that are addressed here. We show that some earlier quantum mechanical calculations of the Mu + H2 reaction, which are highlighted in this review and which have been used to benchmark approximate methods, are in error by as much as 19% in the low-temperature limit. We demonstrate that an approximate treatment of the Born–Oppenheimer diagonal correction that was used in some recent studies is not valid for treating the vibrationally-state-selected reaction. We also discuss why vibrationally adiabatic potentials that neglect bend zero-point energy are not a useful analytical tool for understanding reaction rates and why vibrationally nonadiabatic transitions cannot be understood by considering tunneling through vibrationally adiabatic potentials. Finally, we present calculations on a hierarchical family of potential energy surfaces to assess the sensitivity of rate constants to the quality of the potential surface.},
doi = {10.1080/00268976.2014.951416},
journal = {Molecular Physics, 113(2):160-175},
number = ,
volume = ,
place = {United States},
year = {Fri Jan 09 00:00:00 EST 2015},
month = {Fri Jan 09 00:00:00 EST 2015}
}