The equilibrium constants for water oligomers ranging from dimers to cyclic
hexamers are determined using Wertheim's theory of associating systems. In
the present model for water, the pair potential has a spherical hard core,
and tetrahedral hydrogen bonds which are represented by an energy paramete
r and an interaction volume. On the basis of the present theory, one predic
ts that in earth's troposphere, water dimers and perhaps trimers may contri
bute to the absorption of solar radiation, but concentrations of higher oli
gomers are too low to influence the optical properties of the earth's atmos
phere. (C) 2000 American Institute of Physics. [S0021-9606(00)50340-7].