New Features in the Behavior of Orthopositronium Annihilation Rates near the Vapor-Liquid Critical Point of Ethane

Abstract
Orthopositronium annihilation rates have been measured as a function of density near the vapor-liquid critical point of ethane. An unexpected and sharp enhancement in the annihilation rates is observed at a density of about 115 amagats at 305.45 K. These results are interpreted in terms of density fluctuations in the fluid.