Knowledge Bank

Water vapor lineshifts induced by nitrogen pressure have been measured using FT-spectrometer with multi-pass absorption cell at $0.0025cm-1$ resolution in $1850-2230cm-1$ spectral region. The measurements have been carried out from three spectra with 32 meters absorption path; the $H2O$ pressures being equal to 2, 6 and 5 torr with nitrogen filling equal respectively to 123 and 201 torr for the last two spectra. A special procedure have been used to minimize the errors connected with the assymetry of the contours because of apparatus effects. The fitting of Voigt contour parameters was used to obtain lineshift parameters. Accuracy of lineshift coefficient determination was better than 1 mk/atm. The lineshift coefficients have been determined for well resolved isolated lines of R-branch of $\nu 2$ band with high quantum numbers J up to 18. Their values change from +14.4 to -14.5 mk/atm. The lineshift coefficients have been calculated using the Anderson method and cut-of-free procedure. The dipole-quadrupole, quadrupole-quadrupole, dipole-hexadecapole and polarizational interactions were included in the calculations. The calculations use the fitted parameter - the mean polarizability of the molecule in the (010) vibrational state. The calculated lineshift coefficients agree satisfactory with the measured ones. The contributions of different type of intermolecular potentials and their dependences on J value will be discussed. The research described in this publication was made possible in part by grant N. NY3000 from the International Science Foundation.