Abstract

Ultrafast time-resolved two-photon photoemission has recently been used to probe carrier dynamics at surfaces and interfaces. However, most measurements have been performed at the surface normal, e.g., see¹ In fact, the parallel-momentum-resolved lifetime measurement of image states has not been reported. Here we describe a k-space state-resolved study of imagestate lifetimes, which measures the time evolution of the photoexcited electron population at different points in the momentum space. Image electrons are weakly bound surface electrons with very narrow spectral features. Studies are done on both stepped and flat surfaces in order to understand image electron interactions with a step potential. The results suggest a new relaxation channel for image-state electrons on stepped surfaces.

© 1999 Optical Society of America