NUKLEONIKA 2002, 47(Supplement 1):s47-s51
## ISOTOPE EFFECTS ON VAPOR PHASE 2ND VIRIAL COEFFICIENTSW. Alexander Van Hook^{1}, Luis P.N. Rebelo^{2}, Max Wolfsberg^{3}^{1} Chemistry Department, University of Tennessee, Knoxville TN 37996-1600 USA ^{2} Instituto de Tecnologia Quimica e Biologica, UNL, Apartado 127, 2780-901 Oeiras, Portugal^{3} Chemistry Department, University of California Irvine, Irvine CA 92697-2025 USA
Vapor phase 2nd virial coefficient isotope effects (VCIE’s) are interpreted. A useful correlation is developed between -D(ß- b_{o})(ß-b_{o}) = (-VCIE) and the reference condensed phase reduced isotopic partition function ratio [ln(f_{c}/f_{g})]^{*}. ß is the second virial coefficient, b_{o} = 2ps^{3}/3, s is the Lennard-Jones size parameter, and D is an isotopic difference, light-heavy. [ln(f_{c}/f_{g})]^{*} can be obtained from vapor pressure isotope effects for T/T_{CRITICAL} <0.7. Also (-VCIE) = ln(f_{p}/f_{g}^{2}), where ln(f_{p}/f_{g}^{2}) is the reduced isotopic partition function ratio describing the equilibrium between monomers and interacting pairs. At temperatures well removed from crossovers in ln(f_{p}/f_{g}^{2}) or [ln(f_{c}/f_{g})]^{*}, ln(f_{p}/f_{g}^{2}) = (0.4±0.2) [ln(f_{c}f_{g})]^{*}.
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