Assignments and Intensities of 14NH3 Hot Bands in the 5- to 8-μm (3ν2−ν2, ν2+ν4−ν2) and 4-μm (4ν2−ν2, ν1−ν2, ν3−ν2 and 2ν4−ν2) Regions

✍ Scribed by C. Cottaz; G. Tarrago; I. Kleiner; L.R. Brown

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 855 KB
• Volume: 209
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.2001.8406

✦ Synopsis

To complete the analysis of the complex infrared spectra of 14 NH 3 in the 4-to 8-µm region, we assigned nearly 1200 transitions in the 3ν 2 -ν 2 , ν 2 + ν 4 -ν 2 , ν 1 -ν 2 , ν 3 -ν 2 , 2ν 4 -ν 2 , and 4ν 2 -ν 2 hot bands using the upper state energy levels determined by our previous studies at 4 and 3 µm (J. Mol. Spectrosc. 173, 120-145 (1995); 193, 46-71 (1999)). Line intensities of those hot bands were analyzed using measurements retrieved from 0.0056 and 0.011 cm -1 unapodized resolution FT spectra recorded at Kitt Peak National Observatory. By a least-squares fit of vibrational-inversion transition moments, over 770 intensity measurements are modeled to ±7.2% and ±8.9% in the 5-to 8-µm and 4-µm regions, respectively. The values of the transition dipole moment were determined to obtain the band strengths of hot bands. In the 5-to 8-µm region, the band strengths in cm -2 atm -1 at 296 K of 3ν 2 -ν 2 (a ← s), 3ν 2 -ν 2 (s ← a), ν 2 + ν 4 -ν 2 (s ← s) and ν 2 + ν 4 -ν 2 (a ← a) were found to be 0.000075(23), 0.351(22), 0.689(32), and 0.525(44), respectively. In the 4-µm region, for the ν 3 -ν 2 (s ← s), ν 3 -ν 2 (a ← a), 2ν 4 l 4 =±2 -ν 2 (s ← s), and 2ν 4 l 4 =±2 -ν 2 (a ← a), they were estimated to be 0.0703(32), 0.0599(27), 0.00547(34), and 0.00473( 29), respectively at 296 K. Also, about 100 line intensities of the

, and 4ν 2 -ν 2 (s ← a) weak hot bands were measured and reported. The prediction generated by the present study is available for the detection of 14 NH 3 in exoplanet atmospheres and brown dwarf stars with relatively high temperature (∼1000 K). A few self-broadened linewidths are reported to demonstrate that there is a large variation with the vibrational quanta.