Gas-phase UV absorption spectra of pyrazine, pyrimidine and pyridazine

The gas phase UV absorption spectra of pyrazine, pyrimidine and pyridazine were determined by using a D2-lamp coupled to a monochromator-PM system between 200 and 380 nm, at 353 +/- 3 K and at pressures lower than their vapor pressure (0.08-0.5 torr). The obtained spectra consist of a broad continuum with low intense absorption bands at 200-380 nm. Absorption of the investigated compounds at wavelengths > 290 nm is non-negligible (sigma(lambda) > 290 nm in the order of 10(-20) cm(2) molecule(-1)). These results indicate that, pyrazine, pyrimidine and pyridazine could be removed from the troposphere via photolysis reactions.