The absorption cross section of the nitrate free radical has been scanned by a tunable dye laser with 0.05 nm resolution (FWHM) between 613 and 672 nm, and portions of the region were scanned at high resolution (200 MHz) with the laser in singlehyphen;frequency mode. These data, combined with other recent measurements, give a peak cross section at 661.9 nm of 1.90times;10minus;17cm2; and the integrated cross section over the 0ndash;0 band from 14 910 to 15 290 cmminus;1is 2.02times;10minus;15cm. Two recent studies that were said to disagree because of different peak cross sections are shown to agree in terms of integrated absorption cross section over the 0ndash;0 band. It is confirmed that the spectrum is diffuse even under very high resolution. The 0ndash;0 band is well approximated by two closely spaced Lorentzian functions.
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