TOTAL ION DESORPTION YIELDS OF H2O, D2O, CH3OH, CD3OD AND WATER-METHANOL MIXED ICES IRRADIATED AT 584 ANGSTROM

Preliminary measurements of the total ion desorption yields of several pure and mixed molecular ices have been carried out using the He I 58 4 angstrom resonance radiation as the incident photon beam. The variou s ice samples were prepared at 77 K in an ultrahigh vacuum system. The total ion desorption yields of H2O ices, D2O ices, CH3OH ices, CD3OD ices, H2O-CH3OH mixed ices and D2O-CD3OD mixed ices were determined. M inor isotopic effects on the ion desorption processes of the above-men tioned ices have been observed. There is a clear enhancement in the io n desorption yields of water-methanol mixed ices in comparison with pu re ices. Such data are required in the interpretation of the gaseous a tmospheres of comets, asteroids, icy planets, satellites and rings, an d interstellar icy grains.