On particularities of the vapor pressure measurements of refractory substances at very high temperatures

Vapor pressure measurements of refractory materials at very high pressure remain relevant for constructing adequate equations of state up to the domain of a critical point. In the present paper, an attempt is made to provide a reliable physical ground for the experimental method based on a laser-induced evaporation into the buffer gas, which was used by a number of researchers since the end of 1970s. It is shown that there is a low pressure limit (of roughly $0.1$ bar) intrinsically inherent for this kind of measurements. A developed mathematical model is used for interpretation of some controversial or not sufficiently explained experimental results. The model also provides some hints, which could help make more reliable vapor pressure measurements in the future.