Abstract

We report what is believed to be the first measurement of rotational line broadening of high-temperature water vapor for transition frequencies that range from 1.0 to 2.5 THz (33 to 83 cm^-1). Water-vapor rotational transitions were measured in a near-stoichiometric propane–air flame at 1490 K with THz time-domain spectroscopy. Linewidths were measured for 29 pure rotational transitions in both ground vibrational and ${\nu }_2=1$ vibrational levels with lower state energies ranging from 80 to 2390 cm^-1. Measured widths show a dependence on rotational state energy that roughly follows a thermal distribution with variation between various $J, K_a, K_c$ rotational quantum numbers.

© 1999 Optical Society of America

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