Adsorption of ³He on Cesium

D. Ross, J. A. Phillips, J. E. Rutledge and P. Taborek
J. Low Temp. Phys., 106, 81(1997)

Introduction

Experiment

Results

Discussion

References

Projects Page

Results

Fig. 2 shows a comparison between ³He adsorption and the well understood case of ⁴He adsorption. There are several things to note. The frequency shift for ³He on Cs diverges upon approaching saturation, just as it does on Au, as shown in Fig. 2(a). This indicates that ³He wets both substrates. However there is a step-like feature near Dm= -0.6K. This step is absent for ³He on Au, but is qualitatively similar to prewetting steps found for ⁴He on Cs. Fig. 2(b) shows a ⁴He on Cs prewetting step measured on the same (annealed) Cs substrate used for the ³He measurement shown in Fig. 2(a). The step occurs much farther from saturation and is less steep for ³He than for ⁴He. The width of the step was reduced approximately by a factor of three upon annealing for ³He.

The results for ³He adsorption isotherms measured on the second annealed cesium substrate down to ~0.2 K are plotted in Fig. 3. The data have been corrected for frequency shifts due to the pressure and viscosity of the ³He vapor surrounding the microbalance [9,10]. To prevent the data from overlapping, the data plotted in Fig. 3 are vertically offset. The location of the steps relative to liquid vapor coexistence is nearly constant for all temperatures, but the steps become narrower and steeper as the temperature is lowered.