Line Intensities in the 11- and 7.6-μm-Band of HNO3

MIPAS database: new HNO<sub>3</sub> line parameters at 7.6 µm validated with MIPAS satellite measurements

“…Table 4 presents the averages of the ratios R = Int(MIPAS-2015) / Int(Obs) of line intensities in MIPAS-2015 with the corresponding measured values. It shows that, on average, the line intensities of MIPAS-2015 are about 27 % weaker and 39 % stronger than measured by May and Webster (1989) and Perrin et al (1993), respectively. In view of these diverging results, we decided to measure individual line intensities for nitric acid using a (18) The comparison accounts for the temperature conversion to 296 K; no.…”

“…To the best of our knowledge, individual line intensities have been measured in the 7.6 µm region of the HNO 3 spectrum in only two contributions (May and Webster, 1989;Perrin et al, 1993). Laboratory measurements of individual line intensities are indeed rather difficult for HNO 3 since the line widths (γ Voigt ∼ 0.002 cm −1 in laboratory conditions usually used for this unstable species (296 K and 0.3 hPa)) are of the same order of magnitude as the separation of adjacent lines (from 0.002 to 0.010 cm −1 ), resulting in a lot of blended lines.…”

“…Contrary to the previous analysis (Perrin et al, 1989(Perrin et al, , 1993(Perrin et al, , 1989, the new Hamiltonian model accounts fully for the various vibration-rotation resonances and torsional effects affecting the V3 and V4 bright states and the four dark states 2V6, 3V9, V5 + V9, and V7 + V8. The relative line intensities at 7.6 µm were calculated, also accounting for the observed resonances (Perrin, 2013).…”

“…2 Improved analysis of the 7.6 µm region of HNO 3 At 7.6 µm, the MIPAS-OLD data originate from two laboratory studies, focused on line positions (Perrin et al, 1989) and line intensities (Perrin et al, 1993). The corresponding linelist is limited to the ν 3 and ν 4 bands of the main isotopologue, H 14 N 16 O 3 , and the quality of the corresponding line positions and intensities is rather poor.…”

“…More precisely, Table 3 compares the information available for the 7.6 µm region of HNO 3 in the MIPAS-OLD and MIPAS-2015 databases. It shows that the new database includes lines from four weak bands (2ν 6 , ν 5 +ν 9 , ν 7 +ν 8 and 3ν 9 ) together with those from the ν 3 and ν 4 bands which were already present in MIPAS- OLD: this is because the theoretical model used in 2013 (Perrin, 2013) to generate the linelist is more sophisticated than in 1993 (Perrin et al, 1993).…”