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

Abstract

To complete the analysis of the complex infrared spectra of 14NH3 in the 4- to 8-μm region, we assigned nearly 1200 transitions in the 3ν2−ν2, ν2+ν4−ν2, ν1−ν2, ν3−ν2, 2ν4−ν2 and 4ν2−ν2 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 3ν2−ν2 (a←s), 3ν2−ν2 (s←a), ν2+ν4−ν2 (s←s) and ν2+ν4−ν2 (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 ν3−ν2 (s←s), ν3−ν2 (a←a), 2ν4l4=±2−ν2 (s←s), and ν4l4=±2−ν2 (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 ν1−ν2 (a←s), ν1−ν2 (s←a), 2ν4l4=0−ν2 (a←s), 2ν4l4=0−ν2 (s←a), and 4ν2−ν2 (s←a) weak hot bands were measured and reported. The prediction generated by the present study is available for the detection of 14NH3 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.