THz Laser Study of Self-Pressure and Temperature Broadening and Shifts of Water Lines for Pressures up to 1.4 kPa

Published

September 1, 2004

Author(s)

Vyacheslav B. Podobedov, David F. Plusquellic, Gerald T. Fraser

Abstract

The self-broadened linewidths of pure rotational lines of water vapor have been investigated in the temperature range 263 K to 340 K and over an extended pressure range from 30 Pa to 1400 Pa using an optically pumped THz photomixer spectrometer having a relative precision of {nearly equal to} 10^-5 cm^-1. The lineshapes of several lines between 12 cm^-1 and 52 cm^-1 were best fit to Lorentzian models rather than to any other function over the spectral interval spanning 5 FWHM. The Lorentzian FWHM linewidths varied between 0.67 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, {Δ}Ņ(P), ranged from 0.013 cm^-1atm^-1 to 0.046 cm^-1atm^-1. The measured linewidths also exhibited a (To/T) power law dependence on temperature. The best fit exponent n varied from 0.56 to 0.81 relative to other lines in the set. A decrease in {Δ}Ņ(T) with increasing temperature was also observed and found to vary between (2-5)x10^-3 cm^-1atm^-1 over the 300 K to 340 K temperature range.

Citation

Journal of Quantitative Spectroscopy and Radiative Transfer

Volume

87

Issue

No. 3-4

Pub Type

Journals

Keywords

far IR, lineshape, self, vapor, water

Citation

Podobedov, V. , Plusquellic, D. and Fraser, G. (2004), THz Laser Study of Self-Pressure and Temperature Broadening and Shifts of Water Lines for Pressures up to 1.4 kPa, Journal of Quantitative Spectroscopy and Radiative Transfer (Accessed April 25, 2024)