The neutral muonic helium atom may be regarded as the heaviest isotope of the hydrogen atom, with a mass of ~4.1 amu (4.1H), because the negative muon screens one proton charge. We report the reaction rate of 4.1H with 1H2 to produce 4.1H1H + 1H at 295 to 500 K. The experimental rate constants are compared with the predictions of accurate quantum mechanical dynamics calculations carried out on an accurate Born-Huang potential energy surface and with previously measured rate constants of 0.11H (where 0.11H is shorthand for muonium). Kinetic isotope effects can be compared for the unprecedentedly large mass ratio of 36. The agreement with accurate quantum dynamics is quantitative at 500 K, and variational transition state theory is used to interpret the extremely low (large inverse) kinetic isotope effects in the 10-4 to 10-2 range.
Revised: April 7, 2011 |
Published: January 28, 2011
Citation
Fleming D.G., D.J. Arseneau, O. Sukhorukov, J.H. Brewer, S.L. Mielke, G.C. Schatz, and B.C. Garrett, et al. 2011.Kinetic Isotope Effects for the Reactions of Muonic Helium and Muonium with H2.Science 331, no. 6016:448-450.PNNL-SA-76022.doi:10.1126/science.1199421