Identification of H₂O in the Tail of Comet Kohoutek (1973f).

Spectra of the tall of comet Kohoutek have been obtained in the region 5000-7500 A. They show clearly and fairly strongly the main progression of bands of the H2O+ ion with the required alternation of band structure. Only lines expected to be strong at low rotational temperature (<100 K) are observed in the cometary bands. The spin-splitting has been resolved for those "lines" for which it is known to be large from laboratory data. The identification of H2O+ in the tall of comet Kohoutek provides the first conclusive evidence for the presence of H2O in comets. Subject headings: comets - spectra, molecular