Experimental Determination of a Two-Dimensional Liquid-Vapor Critical-Point Exponent

Abstract

The liquid-vapor coexistence boundary of submonolayer C${\mathrm{H}}_{4}$ adsorbed on graphite was mapped out in an extensive ac heat-capacity study. The order-parameter exponent $\ensuremath{\beta}$ that describes the shape of the liquid-vapor coexistence boundary was found to be 0.127 \ifmmode\pm\else\textpm\fi{} 0.020. This is in good agreement with $\frac{1}{8}$, the exact value calculated for a two-dimensional Ising-model system.