Water vapor continuum: Whether collision-induced absorption is involved?

•Controversies in collision-induced absorption (CIA) definition are discussed.•Possible relation among CIA and the water vapor continuum are considered.•The importance of proper statistical weighting of various pair states is emphasized.•Crucial role of quasi-bound dimer states in continuum absorption is pointed out.

In a series of recent publications, the idea is pursued to shed a new light on the theory of the water vapor continuum absorption invoking the mechanism of collision-induced absorption. In the opinion of the present author, a portion of theoretical suggestions on this subject is biased and may thus lead to untenable conclusions about the nature of the continuum. The most typical drawback consists of improper consideration of statistics in the ensemble of interacting monomers that lead to embedding incorrect statistical weights to various types of molecular pairs which can form. The current note aims at clarifying the term “collision-induced absorption” in order to avoid incongruity in understanding the nature of the water vapor continuum.