Absolute sputtering yields have not been measured for many
mixed ices. Since ice sputtering
is affected by chemistry simple models work only approximately.
For a trace species in an ice
matrix a good approximation is to assume the trace species
leaves at the same rate as the matrix
if the yield is large. In other cases we recommend
weighting the yields by the surface area
Y = c1 Y1 + c2 Y2,
where the Yi are the yields for the individual species.