Experimental absolute intensities of the 4ν9 and 5ν9 O-H stretching overtones of H2SO4

This work uses cavity ring-down spectroscopy to measure two high vibrational overtones (4ν9 and 5ν9) of the O-H stretch in sulfuric acid. The frequencies, bandwidths, and intensities are obtained for these previously unobserved transitions. The atmospheric J-values for the overtone-induced photodissociation are calculated using the experimental cross-sections. Accurate J-values are essential for understanding the formation of the springtime polar sulfate layer by overtone-induced dehydration of H2SO4. The results are compared to previous experimental and theoretical studies of sulfuric acid.