We have studied the effect of He-3 dilution on very thin superfluid He-4 fi
lms using a torsional oscillator technique. Assuming that the inert layer i
s free of He-3, we obtain data on films with He-3 concentration in the supe
rfluid layer up to 80%. We compare our results with data available from ear
lier studies. (C) 2000 Elsevier Science B.V. All rights reserved.