Large Anharmonic Effects on Tunneling and Kinetics: Reaction of Propane with Muonium

Calculations of kinetic isotope effects (KIEs) provide challenging tests of quantal mass effects on reaction rates, and muonium KIEs are the most challenging. Here, we show that it can be very important to include reaction-coordinate-dependent vibrational anharmonicity along the whole reaction path to calculate tunneling probabilities and KIEs. For the reaction of propane with Mu, this decreases both the height and width of the vibrationally adiabatic potential barrier, with both effects increasing the rate constants. Our results agree well with the experimental observations.

Automated summary

The study reveals that considering reaction-coordinate-dependent vibrational anharmonicity is crucial in calculating tunneling probabilities and kinetic isotope effects. In the reaction of propane with Mu, this decreases the height and width of the vibrationally adiabatic potential barrier, leading to increased rate constants, which is in good agreement with experimental observations.