COLOR-CENTERS IN UV-IRRADIATED NITRATES

We show that the peroxonitrite anion, ONOO-, is a primary product when solid nitrates are irradiated with 254-nm UV and is the source of the yellow color. Many previous investigators have attempted to interpret photolysis processes in crystalline nitrates as primarily involving nitrite anions and oxygen gas, not realizing that the nitrite and oxygen can be formed by decomposition of peroxonitrite when the solid is dissolved for analysis. A small amount of nitrite is formed in nitrate crystals directly from the nitrate ions but much of it is generated by photolysis of the peroxonitrite anion.