Absolute infrared absorption cross sections for ClONO₂ at 296 and 223 K

The infrared absorption spectrum of chlorine nitrate has been measured at 296 K and at 223 K, a temperature typical of the stratosphere. Absorption cross sections are reported for all the strong features of the absorption spectrum between 450 and 2000 cm −1 . These cross sections may be used in determining stratospheric ClONO 2 concentrations. The ν 4 , ν 3 , and ν 2 transitions near 780, 809, and 1292 have been studied in detail, and some significant temperature dependencies in the cross sections have been found. The most dramatic of these is the 34% increase in the Q branch at 780.2 cm −1 between 296 K and 223 K.