POSITRONIUM IN ALPHA-QUARTZ .2. POSSIBLE EFFECT OF DAMPING OF POSITRONIUM QUASI-PARTICLE ON THE MOMENTUM DISTRIBUTION

A part of the observed momentum spread of thermalized positronium in crystalline quartz reported in Part I could be attributed to a damping effect of the positronium quasiparticle in the phonon field. As analogized from the case of excitons, the damping constant (the width of the spectral function) for the quasiparticle state is expected to be proportional to the absolute temperature T in the moderate and high temperature regions due to the well-known motional effect in the phonon field. Therefore if we analyze, as in Part I, the observed momentum distribution by using a Maxwellian with effective mass M∗(T), the resultant M∗(T) would appear to increase with increasing temperature owing to the above-mentioned temperature dependence of the damping effect. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.