EFFECT OF MOLECULAR ASSOCIATION ON ELECTRICAL CONDUCTIVITY OF SODIUM VAPOUR

The electrical conductivity of sodium vapour at pressures above 10 torr cannot be calculated satisfactorily on the assumption that the vapour is monatomic. A theoretical assessment shows that clusters of three and four sodium atoms, which have exceptionally low ionization potentials, may make contributions to the conductivity out of all proportion to their concentrations, to the extent that under nearsaturated conditions their influence could predominate by an order of magnitude. The conclusions of this paper apply to all alkali metal vapours, and possibly to other metallic vapours also.