Electron-Electron Interactions Continuously Variable in the Range $2.1>\mathrm{}{r}_{\mathrm{s}}>0.9\mathrm{}$

We present the results of an experimental study of the enhancement of the effective mass and its dependence on electron density. The study of this phenomenon in a two-dimensional electron gas, whose density may be varied continuously, allows for the first time a comparison for different values of $r_s$ within the same material.