The temperature dependence of the NO3 absorption spectrum was measured
over the wavelength range 440-720 nm and temperature range 298-200 K
using a diode array spectrometer. The NO3 absorption cross section at
662 nm, the peak of the 0-0 transition, was measured using time resolv
ed tunable diode laser absorption following 351 nm laser photolysis of
a Cl-2/ClONO2 mixture. The NO3 absorption cross section at 662 nm was
(2.23 +/- 0.22) x 10(-17) cm(2) at 298 K and increased 36% in going f
rom 298 to 200 K (2 sigma error limits including estimated systematic
errors). These results are quantitatively compared with previous measu
rements.