On the origin of the band structure observed in the collision-induced absorption bands of CO2

The 313–220 rotational transition of water vapor at 183 GHz was studied using modern resonator spectroscopy methods at atmospheric pressures in the broad frequency range 130–205 GHz down to far wings. The experimental method of sample substitution for the exclusion of the apparatus function was used. The air broadening parameter value was defined as 3.84± 0.04 MHz/Torr at 298 K. The observed atmosphere water vapor line center was found to be shifted down at about 53 MHz from the line center at low pressures, which gives a value of -0.07±0.02 MHz/Torr for the air pressure shift parameter. Measurements of broadening and shifting of the water line in pure nitrogen and oxygen atmosphere were also performed. Calculated then parameters of air broadening and shifting agree with directly measured ones within the errors quoted. Measurement of the integral intensity of the line was done. The directly measured integral line intensity coincides with a value given in GEISA and HITRAN databases within experimental error. The results are compared with previous experimental laboratory and satellite data.