Knowledge Bank

The high resolution spectra of the second overtone of the OH stretch of trans-nitrous acid HONO, were recorded using intraCavity Laser Absorption Spectroscopy between 10220 and $30150cm-1$. The spectra were analyzed to yield a complete set of rovibrational parameters, including the A,B and C rotational constants. In the atmosphere, HONO is photolyzed to from the hydroxyl radical by UV radiation during daytime hours, and during early morning and late evening hours when UV radiation is not prevalent, visible excitation of the OH overtone could provide an alternative route to HONO photodissociation. Atmospheric models that include overtone-induced process require accurate measurements of overtone intensities, but in many case rely on estimates that are extrapolated from the intensity of the fundamental. We measured the band intensity of the second overtone of the OH stretch and calculated the contribution of the overtone-induced mechanism to the photolysis of HONO.