A. Bauer

Temperature and perturber dependences of water vapor line-broadening. Experiments at 183 GHz; calculations below 1000 GHz

Measurements of linewidths of the 313 ← 220 H2O line at 183 GHz are presented. These include broadening by H2O, N2, O2, and Ar with the temperature dependence in the 300–390 K range. The room-temperature experiments are in good agreement with previous results. Systematic calculations of H2O line-broadening parameters of lines centered below 1000 GHz are also presented. These have been performed for a recently developed and successfully tested model. Tabulations of the room-temperature values and temperature dependence for self-, N2-, O2-, air-, and CO2-broadening are given. These data should be useful for spectral calculations required by atmospheric applications.

Temperature and perturber dependences of water-vapor 380 GHz-line broadening

Experimental results on the collisional broadening of the 41,4→32,1H2O rotational-line at 380 GHz are presented. Accurate measurements of self-, N2-, O2-, and Ar-broadened widths in the 300–373 K temperature range and values for the pure H2O line-shifts are presented. Comparisons are made between the experimental data and predictions of a theoretical model recently developed by the authors. The influence of resonance and kinetic effects on the dependence of widths on temperature are pointed out. It is shown that these effects strongly depend on the colliding partner.

Self- and air-broadened linewidth of the 183 GHz absorption in water vapor

Abstract The linewidth of the 3 1.3 ← 2 2.0 rotational transition of water vapor at 183 GHz has been investigated using a video millimeter wave spectrometer equipped with a signal digitizer. Self- and air-broadening parameters have been obtained for four temperatures over the 299−251 K range; the results are compared with previous experimental and theoretical data.

Water vapor absorption in the atmospheric window at 239 GHz

Absolute absorption rates of pure water vapor and mixtures of water vapor and nitrogen have been measured in the atmospheric window at 239 GHz. The dependence on pressure as well as temperature has been obtained. The experimental data are compared with several theoretical or empirical models, and satisfactory agreement is obtained with the models involving a continuum; in the case of pure water vapor, the continuum contribution based upon recent theoretical developments gives good results. The temperature dependence is stronger than that proposed in a commonly used atmospheric transmission model.

Laboratory studies of water vapor absorption in the atmospheric window at 213 GHz

Abstract Absolute absorption rates of water vapor have been measured in the atmospheric window between the rotational lines at 183 and 321–325 GHz. Measurements have been carried out for pure water vapor and mixtures with N2 at atmospheric pressure. Pressure and temperature dependences are compared with models involving different lineshapes and different types of continua.

Temperature dependence of water-vapor absorption in linewings at 190 GHz

Abstract Absolute absorption rates of water vapor have been measured in the high-frequency wing of the 183 GHz rotational line. Measurements have been carried out for pure water vapor and mixtures with N 2 at atmospheric pressure. Pressure and temperature dependences are compared with models involving different types of lineshapes.

Absorption by H2O and H2O-N2 mixtures at 153 GHz

New experimental data on and a theoretical analysis of the absorption coefficient at 153 GHz are presented for pure water vapor and water vapor-nitrogen mixtures. This frequency is 30 GHz lower than the resonant frequency of the nearest strong water line (183 GHz) and complements our previous measurements at 213 GHz. The pressure dependence is observed to be quadratic in the case of pure water vapor, while in the case of mixtures there are both linear and quadratic density components. By fitting our experimental data taken at several temperatures we have obtained the temperature dependence of the absorption. Our experimental data are compared to several theoretical models with and without a continuum contribution, and we find that none of the models is in very good agreement with the data; in the case of pure water vapor, the continuum contribution calculated using the recent theoretical absorption gives the best results. In general, the agreement between the data and the various models is less satisfactory than found previously in the high-frequency wing. The anisotropy in the observed absorption differs from that currently used in atmospheric models.

Temperature dependence of water-vapor absorption in the wing of the 183 GHz line

Abstract Absolute absorption rates of water vapor have been measured in the laboratory in the high-frequency wing of the 183 GHz line. Measurements have been carried out for pure water vapor and mixtures with N 2 at atmospheric pressure. Pressure- and temperature-dependences are compared with models involving several types of lineshapes.

Continuum in the windows of the water vapor spectrum. Absorption of H2O-Ar at 239 GHz and linewidth calculations

Abstract Absolute absorption rates of mixtures of water vapor and argon have been measured at 239 GHz, which is an atmospheric window for the rotational spectrum of water vapor. The dependence on pressure as well as temperature has been obtained. The experimental data are compared with models using conventional line profiles. As these models require the knowledge of the collisional linewidths of H2O broadened by Ar, theoretical calculations using the Robert-Bonamy formalism have been carried out. A continuum effect is observed when comparing the experimental absorption with the models, as well as for the magnitude of the absorption discrepancy and for the strong temperature dependence of this absorption. The effect, when compared to the collisional broadening efficiency, is about the same as that observed for H2ON2.

Millimeter wave farwings of water vapor in N2 and CO2 atmospheres

Absolute absorption has been measured in the laboratory for H2O−N2 and H2O−CO2 mixtures at 239 GHz, in the atmospheric window of the H2O rotational spectrum. Both data are compared to existing models.