VACANCY FORMATION ENERGY IN MOLECULAR SOLID CH₄

The Doppler broadening energy spectra have been measured on high-purity condensed CH₄ in temperature range from 30K to 105K. In solid phase and below the melting point, the variations of S-parameter with temperature were interpreted as o-Ps trapped in the thermally activated vacancy-type defects. A vacancy formation energy of 0.10±0.02eV was derived by positronium trapping model.