Spectroscopic Evidence for Long-Range Repulsive Intermolecular Forces

Abstract

Experimental results are presented on the shift of wavelength of absorption of benzene, naphthalene, pyrene, and phenanthrene with density of the diluents helium and nitrogen. Arguments are presented to show that the blue shift observed in the benzene ¹L_b spectrum in helium is neither due to short‐range repulsive forces nor to long‐range dispersive forces. It is presumed that there are weak, long‐range, nondispersive forces present in the benzene‐helium interaction that have the character of repulsive forces.