Microwave spectroscopy of the muonium state in BeO

Abstract The remarkable thermal, optical and mechanical properties of beryllium oxide lead to a number of applications, however little is known about the behaviour of hydrogen in BeO, which can be as high as 4% in thin films. We used positive muons as a model for hydrogen. Earlier TF data shows both diamagnetic and muonium states and a large “missing fraction”. We measured the muonium fraction using microwave resonance and a novel design of microwave cell which allows “flypast” operation with a small sample. The muonium fraction is found to be larger than that measured by TF-muSR — also unlike the decrease seen in the TF result, the amplitude increases slightly in the range 300–400 K. Measurements with delayed RF pulses showed a small increase in muonium fraction at base temperature at later times.