Evidence for the formation of NeMuast;, an isotopic analog of the Rydberg molecule NeHast;, has been obtained from the observation of chemiluminescent emission in the nearhyphen;infrared region. This is thefirstspectroscopic detection of a muoniumhyphen;containing molecule. NeMuast; was formed by stopping a 4 MeV muon (mgr;+) beam in a target vessel containing 1ndash;6 atm of Ne and sim;1 Torr Ar. The wavelength spectrum of the emission, from sim;680ndash;1000 nm, was measured using a variablehyphen;wavelength filter, with a resolution of plusmn;12.5 nm. Lower resolution spectra were also taken with a series of long pass filters. A complete histogram of photon events vs time was collected for each wavelength. Two strong transitions are observed, centered at 818 and 943 nm. Identification of NeMuast; was made by a comparison of the experimental spectrum with a simulated spectrum based on detailedabinitiocalculations, extended to higher excitation levels than had heretofore been reported. Both experimental and theoretical results are reported here. Although the mechanism by which the emitting states in NeMuast; are formed remains unclear, radiolysis effects appear to play a dominant role, indicating that NeMu+(the product of muon thermalization in Ne) undergoes charge exchange with metastable Arast; and/or is neutralized by a spur electron, both species produced during the slowing down of the high energy muon.
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