Emission Lines in the Spectrum of IO

Spectrograms of Io obtained with the 2-m reflector at the Shemakha Astrophysical Observatory, at dispersions of 12 and 15 A/mm have been used to study profiles of Na I, Fe I, Mg I, and Ca I emission lines. The line profiles were found to be asymmetric. It is shown that variations of the intensity ratio D2/D1 in the spectrum of Io do in fact occur, varying within the limits 1.6 plus or minus 0.3. The intensity of the sodium D-line at Phi = 90 deg is about 40% higher than at Phi = 270 deg. The number of radiating neutral sodium atoms and the lower limit of the number of radiating iron, magnesium, and potassium atoms along the line of sight are calculated.