## Abstract

Experimental data on vapor phase second virial coefficient isotope effects (VCIEs) are reviewed and then interpreted using the general theory of isotope effects. Useful correlations are developed between -δ(ℬ - b_{o})/(ℬ - b_{o}) = (-VCIE) and [ln(f_{c}/f_{g})]*, where [ln(f_{c}/f_{g})]* is the reference condensed phase reduced isotopic partition function ratio, and ℬ is the second virial coefficient, b_{o} = 2πσ^{3}/3, σ is the Lennard-Jones size parameter, and δ denotes an isotopic difference, light-heavy. [ln(f_{c}/f_{g})]* can be straightforwardly obtained from measurements of vapor pressure isotope effects for T_{R} = T/T_{CRITICAL} < 0.7. We show (-VCIE) = ln(f_{p}/f_{g}^{2}) where ln(f_{p}/f_{g}^{2}) is the reduced isotopic partition function ratio associated with the equilibrium between isolated gas-phase monomer species 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) [in(f_{c}/f_{g})]*.

Original language | English |
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Pages (from-to) | 9284-9297 |

Number of pages | 14 |

Journal | Journal of Physical Chemistry A |

Volume | 105 |

Issue number | 40 |

DOIs | |

Publication status | Published - 11 Oct 2001 |