THz laser study of self-pressure and temperature broadening and shifts of water vapor lines for pressures up to 1.4 kPa
✍ Scribed by V.B Podobedov; D.F Plusquellic; G.T Fraser
- Publisher
- Elsevier Science
- Year
- 2004
- Tongue
- English
- Weight
- 329 KB
- Volume
- 87
- Category
- Article
- ISSN
- 0022-4073
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✦ Synopsis
The self-broadened linewidths of pure rotational lines of water vapor have been investigated in the temperature range 263-340 K over a pressure range from 30-1400 Pa using an optically pumped THz photomixer spectrometer having a relative precision of ≈ 10 -5 cm -1 . The lineshapes of several lines between 12 and 52 cm -1 were well ÿt by Lorentzian proÿles over the spectral interval spanning ±5 FWHM. The Lorentzian FWHM linewidths varied between 6:6 × 10 -6 and 1:06 × 10 -6 cm -1 Pa -1 (0.67 and 1:07 cm -1 atm -1 ) and were found to depend on the J; K a and K c quantum numbers as well as temperature. The observed pressure-induced shifts, (P), ranged from 1:3 × 10 -7 -4:5 × 10 -7 cm -1 Pa -1 (0.013-0:046 cm -1 atm -1 ). The measured linewidths also exhibited a (T 0 =T ) n power law dependence on temperature. The best ÿt exponent n varied from 0.56 to 0.81, dependent on rotational line. A decrease in (T ) with increasing temperature is also observed, varying between 2 × 10 -8 and 5 × 10 -8 cm -1 Pa -1 (2 × 10 -3 and 5 × 10 -3 cm -1 atm -1 ) over the 300-340 K temperature range.