Pressure-broadening of water lines in the THz frequency region: Improvements and confirmations for spectroscopic databases. Part I

The self-, nitrogen- and oxygen-broadening of the J = 7(2,5) - 8(1,8) (1.147 THz), 8(5,4) - 7(6,1) (1.168 THz), 7(4,4) - 6(5,1) (1.173 THz), 8(5,3) - 7(6,2) (1.191 THz), and 6(3,3) - 5(4,2) (1.542 THz) rotational transitions of water vapor have been experimentally and theoretically investigated in the present work, showing that the corresponding HITRAN selfbroadening parameters are affected by large errors. Indeed, simple semiclassical calculations performed for more than 1500 rotational water lines with wavenumber below 1000 cm-1 allow us to improve the self-broadening values reported in the HITRAN database when obtained by assuming a J dependence. On the other hand, our measurements and calculations confirm the values reported in the HITRAN database for air-broadening and shift, which are based on semiclassical computations as well. On the whole, the present investigation provides new experimental as well as theoretically improved values for self-broadening parameters of rotational lines in the THz frequency region.