Photolysis of crystalline alkali nitrates via excitation of NO3– to the state of symmetry 21E1|

•We studied photochemical transformations in alkali metal nitrates under the action of UV light with a wavelength of 172 nm.•Photolysis at 77 K exhibits the formation of fragment NO2, O– and O3– radicals.•The formation of radical products on the regular nitrate ion was not observed under photolysis both at 300 K and at 77 K.

Photolysis of crystalline alkali nitrates has been studied using optical, IR, and EPR spectroscopy and chemical analysis of the aqueous solutions of the exposed samples. Excitation of the nitrate ion to 21E1| (а1| ⟵ е|) state by exposure to light with wavelength of 172 nm at 300 K leads to formation of nitrite and peroxynitrite ions. The photolysis at 77 K results in formation of fragment NO2, O–, and O3– radicals. The quantum yields of the nitrite and peroxynitrite ions were calculated. The nitrite ions and peroxynitrite ions are formed in deep layers of the samples. The mechanism of radical formation is connected with photochemical transformations of the nitrate ion in the surface layer of the crystal.

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