Isotopic Dependence of Vapor Pressure in Xenon

The vapor pressure isotopic effect (VPIE) of xenon has been measured using cryogenic distillation. The still is calibrated with argon and krypton and yields a measurement of ln(p ₁₃₀/p ₁₃₆) ≃ (0.26 ± 0.04) × 10^-3, where p ₁₃₀ and p ₁₃₆ are the vapor pressures of ¹³⁰Xe and ¹³⁶Xe at the nominal boiling point, respectively. The dependence of the VPIE across the isotopes for the three elements is found to be approximately linear with atomic mass, and all values are consistent with theoretical expectations.