The water-vapor laser

Water-vapor lasers oscillate on more than a hundred pulsed lines and over a dozen CW lines over the wavelength range from 7 to 220 μ (1300-45 cm^-1). Nearly eighty of these lines are now identified as vibrational-rotational and pure rotational transition in the low-lying vibrational states of the water-vapor molecule. The structure of the water-vapor molecule is reviewed, and the mechanisms responsible for creating population inversions in water-vapor discharges are discussed. It is shown how a model, based on perturbations between rotational levels of different vibrational states, can be used to explain the laser action and to predict new laser lines. Detailed summaries of data on all observed laser lines in H2O¹⁶, H2O¹⁸, and D2O¹⁶and their identifications are presented. Some of the lines are newly reported, and more accurate wavelength measurements have been made for many of the lines. The observation of predicted laser lines in H2O¹⁸is shown to be a strong confirmation of the perturbation model. The list of references contains a fairly complete bibliography of previous work on the water-vapor laser, and a representative bibliography of work on the energy-level structure of the water-vapor molecule.