Rates and Temperature Dependence for the Reaction of Muonic Helium with Ammonia

Abstract

Temperature-dependent reaction rates have been measured for the reaction of muonic helium with ammonia 4.11 H + NH 3 ↔ 4.11 HH + NH 2 where 4.11 H representsthe muonicHeatom–Hewithone electron replacedbyanegative muon–whichbehaves chemicallyasaveryheavyisotopeofhydrogen,as emphasizedbythe (nonstandard)symbol. The Arrhenius activation energy was measured as 47 ± 17 kJ/mol between 400 and 600 K. The large uncertainty easily overlaps the value of 57 kJ/mol measured for the normalH + NH3 reaction [Ko et al., J. Phys. Chem. 94 (1990) 1401], and also existing calculations. The use of NH 3 as the electron donor in the production of neutral muonic He is discussed in light of the title reaction, and in comparison with alternatives Xe and CH 4 .