Some new results on the continuum absorption of water vapor in the thermal i.r. between 8 and 14μm are presented along with a brief review of currently adapted empirical and semi-empirical models explaining its nature. The original suggestion by Penner1 that the observed absorption might be by dimers of water molecules in the vapor phase is reexamined in light of the new results.
Papers with the following subject areas are suitable for publication in the Journal of Quantitative Spectroscopy and Radiative Transfer:
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Infrared absorption by the water vapor continuum near 1200 cm-1 has been measured with a lead-tin-telluride diode laser over a 40.5-m optical path. The measurements were made as a function of temperature from 333 K to 473 K; thus, they overlap and extend previous measurements made at temperatures between 293 K and 388 K. Over the entire temperature range studied here, the continuum extinction coefficient increases quadratically with water-vapor partial pressure as expected for the relatively high partial pressures used in these measurements. At temperatures below 398 K. our measured extinction coefficients agree well with previously reported data. At higher temperatures, however, the extinction coefficient is almost independent of temperature and is substantially larger than predicted by empirical formulas. Values of the self-broadening coefficient for water vapor have been extracted from the experimental data, and a possible interpretation of the results involving both dimer and line-broadening effects is presented.
