Calculated two-photon electronic transitions in sulfuric acid and its atmospheric relevance

We have calculated two-photon electronic transitions for sulfuric acid ( H 2 SO 4 ) in the ultraviolet region using coupled cluster quadratic response theories combined with correlation consistent basis sets. We have investigated how the intensity of two-photon electronic transitions in H 2 SO 4 depends on the wavelength of the photons absorbed. We find that the intensity is more or less constant in the wavelength region in which the density of solar flux is of any importance. We have calculated the J-values for the photodissociation of H 2 SO 4 with absorption of two photons and compared these with previously calculated J-values for one-photon absorption. We find that two-photon electronic transitions of H 2 SO 4 are not a significant mechanism in the photodissociation of H 2 SO 4 .