Isotope Effect in the Band Spectrum of Sodium Hydride

Abstract

As has been pointed out by Hoist and Hulthén¹, the elementary theory of isotopy in band spectra cannot account for shifts and the constants of deuterides, determined with the highest precision. They find it necessary, in calculating the reduced mass of the molecule, to add a correction for the electronic masses, which are supposed to partake fully in rotation and vibration. Since this correction is quite general, one would expect it in all deuterides determined with sufficient precision. The only reported cases which fulfil this prescription are: A1H/A1D ², calculated ratio of the reduced masses CaH/GaD ³, calc. ² = 0·51276, observed ² = 0·51337, and from an investigation of NaD by the present author.