Theory of the magnetic and spectroscopic properties of neptunium hexafluoride

Abstract

The magnetic properties and the optical absorption spectrum of NpF 6 are interpreted on the basis of an appropriate model for the molecule. The theory, in its simplest form, is not in perfect accord with all the available data. Consequently, various physical effects such as covalence, vibronic interactions, the Coriolis force on the unpaired electron, and the Jahn–Teller effect, which might affect the agreement of theory and experiment are discussed in a qualitative or semi-quantitative way. It is pointed out that the g value may vary with temperature so that one must be cautious when comparing the paramagnetic resonance and susceptibility data with theoretical predictions. The Coriolis interaction between the electron (effective) spin and the molecular rotation is sufficiently large to modify the magnetic resonance frequency by an appreciable amount when rotation is free, which is very probably why no paramagnetic resonance has been observed in gaseous NpF 6 . Experiments which would help to clarify the interpretation are suggested.