Relaxation of the Excited Rydberg States of Surface Electrons on Liquid Helium

We report the first direct observation of the decay of the excited-state population in electrons trapped on the surface of liquid helium. The relaxation dynamics, which are governed by inelastic scattering processes in the system, are probed by the real-time response of the electrons to a pulsed microwave excitation. Comparison with theoretical calculations allows us to establish the dominant mechanisms of inelastic scattering for different temperatures. The longest measured relaxation time is around 1 mu s at the lowest temperature of 135 mK, which is determined by the inelastic scattering due to the spontaneous two-ripplon emission process. Furthermore, the image-charge response shortly after applying microwave radiation reveals interesting population dynamics due to the multisubband structure of the system.

Automated summary

This study reports the first direct observation of the decay of excited-state population in electrons trapped on the surface of liquid helium. The relaxation dynamics, governed by inelastic scattering processes, were probed by the real-time response of electrons to pulsed microwave excitation. Comparison with theoretical calculations helped establish the dominant mechanisms of inelastic scattering at different temperatures.