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The formation and reactivity of positive Muon molecular ions

University of British Columbia

Thermal (117—445 K) ion—molecule reaction rates are measured, using the µSR technique, for the muonated molecular ions HeMu+, NeMu+, ArMu+, and N²Mu+ reacting with a wide variety of polar and non-polar neutral species. Mu is a light (0.11 amu) isotope of H with a positive muon replacing the proton. In almost all cases, both charge- and muon-transfer reactions are observed. Since charge transfer is endothermic in many cases, the reaction is believed to occur from rovibrationally excited states, (HeMuj* and (NeMu+)*, in accordance with the low efficiencies of He and Ne moderators for collisional deactivation. The total experimental rate constants are generally in good agreement with capture theories (Langevin, ADO, AADO) and in excellent agreement with the few corresponding protonated ion measurements, regardless of the degree of internal excitation. The reacting muonated ions are found to form by association of a µ+ with the bath gas at muon kinetic energies <1 eV, and much of the binding energy is retained as rovibrational excitation. Collisional deactivation was investigated by varying the bath gas pressure (500~3000 torr) and by adding 0~2 torr Ar. A mechanism of de-excitation of (NeMuX+)* (for reactive gas X) is suggested, while direct quenching of (NeMu+)* and (HeMu+)* is less important, though it does occur.

Thesis/Dissertation

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2008-12-12

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http://hdl.handle.net/2429/2885

Chemistry

University of British Columbia

UBCV

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