COMPUTATION OF TUNNELING RATES IN TIME-DEPENDENT ELECTRIC-FIELDS - ELECTRONS ON THE SURFACE OF LIQUID-HELIUM, A ONE-DIMENSIONAL HYDROGEN-ATOM

We have solved, by numerical methods, the time-dependent Schrodinger e quation for the known potential of electrons over the surface of liqui d helium. The computed tunneling rates for a static field agreed with experimental measurements of the rates. We describe here the extension of the computation to time-dependent electric fields. The results pro vide quantitative details of the amplitude and frequency dependence of the tunneling rates. They show very large photoassisted enhancements of the tunneling rates. In addition, we find a modulation of the tunne ling rates at the frequency of the applied field. The modulation ampli tude decreases sharply at frequencies that are integer fractions of th e frequency corresponding to the energy difference between the electro n ground state and the top of the barrier. We find no evidence of fini te transit-time effects.