Ultraviolet absorption spectra of cis and trans potassium peroxynitrite (KOONO) in solid argon

Two conformers (cis and trans) of potassium peroxynitrite (KOONO) were produced in an argon matrix containing potassium nitrate (KNO3) at 13 K by means of in situ photolysis with an ArF excimer laser at 193 nm. Photoconversion among cis- and trans-KOONO, and KNO3, was achieved on irradiation of the matrix with a laser at varied wavelengths. With the aid of the relative intensities of IR absorption lines observed for each species at each stage of photolysis, the UV absorption spectra of cis- and trans-KOONO were determined. The absorption maxima, near 325 and 375 nm for cis- and trans-KOONO, respectively, agree with theoretical calculations by Krauss. The photolytic behavior of both conformers at varied wavelengths can be understood in relation to the observed UV absorptions.