Prewetting Transitions in a Near-Critical Metallic Vapor

Abstract

Velocity of sound measurements at 10 MHz in near-critical liquid and vapor mercury up to supercritical temperatures and pressures of 1900 K and 1800 bars, respectively, demonstrate the existence of a wetting transition on the walls of molybdenum and niobium cells at ${T}_{W}\ensuremath{\simeq}1250\mathrm{K}$, together with an associated first-order prewetting line in the dense mercury vapor that terminates at a prewetting critical point $({T}_{c,\mathrm{pre}}{,p}_{c,\mathrm{pre}})\ensuremath{\gtrsim}(1860\mathrm{K},\phantom{\rule{0ex}{0ex}}1830\mathrm{bars})$ lying above the bulk mercury critical point at $({T}_{c}{,p}_{c})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(1764\mathrm{K},\phantom{\rule{0ex}{0ex}}1670\mathrm{bars})$.