Microwave Dimensional Resonances in Large Electron-Hole Drops in Germanium

In optically excited Ge at T=1.5 to 4 K, we observe a series of new microwave resonances at 3 to 20 kOe for ν=25 GHz. The resonant fields increase markedly with light intensity and are strongly correlated with the 709-meV electron-hole drop luminescence. We interpret the new lines as magnetoplasma dimensional resonances of single drops of {~} 1 mm diam. We use magnetoplasma dimensional resonance as a direct probe of drop size and kinetics.