The absolute absorption cross sections for the Δ v = 3 and Δ v = 4 OH local mode transitions in room-temperature, gas-phase nitric acid have been measured and calculated ab initio. The measured [calculated at the QCISD/6-31+G(d,p) level] oscillator strengths are (2.9 ± 0.3) × 10 -8 [2.78 × 10 -8 ] and (2.7 ± 0.3) × 10 -9 [2.14 × 10 -9 ]. Scaling the calculated values by 1.15 (the average ratio of measured:calculated ) yields predicted oscillator strengths for transitions to v = 5 and v = 6 of 2.9 × 10 -10 and 4.0 × 10 -11, respectively, corresponding to integrated absorption cross sections of 2.6 × 10 -22 and 3.5 × 10 -23 cm 2 molecule -1 cm -1, respectively for these transitions. These values are almost 2 times larger than previously estimated.
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Donaldson et al. (1998) studied this question.