NIST logo

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

NIST Authors in Bold

Author(s): Vyacheslav B. Podobedov; David F. Plusquellic; Gerald T. Fraser;
Title: THz Laser Study of Self-Pressure and Temperature Broadening and Shifts of Water Lines for Pressures up to 1.4 kPa
Published: September 01, 2004
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, Ka and Kc 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
Keywords: far IR;lineshape;self;vapor;water
Research Areas: