Study of evaporation of C_(60) and C_(70) in vacuum and inert gases

摘要

The goal of the present investigations is the determination of gaseous binary diffusion coefficients which result from evaporation of the fullerenes C_(60) and C_(70) in the presence of an inert gas.The coefficients are obtained with an entrainment method modified by a controlled low pressure system.Powdered fullerene of about 100 mg in weight is evaporated from a small cell through a capillary outlet of about 2 cm in length and an inner diameter of about 0.2 cm.High purity (5N grade) helium,argon or nitrogen is passed over the capillary end with flow rate of about 0.15 standard liters per minute at a constant total pressure between SO and 100 mbar.This particular method saves enormous time for the measurements,in particular,of materials with a low vapor pressure such as the fullerenes.