Abstract

Dynamics of electrons in solids is important to many phenomena such as optical, electrical, magnetical, and chemical properties of matter. Direct measurements of electron-electron (e-e) scattering rates provide critical tests for many body theories. Recent developments in ultrafast laser technology make it possible to probe directly femtosecond phenomena such as e-e scattering in metals. As a consequence of a large cross section for electron scattering hot-electon lifetimes in metals are in femtosecond regime, and until recently the scattering rate could only be evaluated by indirect measurements of heat and electrical transport properties. Two-photon time-resolved photoemission (TPTRP) measures the direct change of hot-electron population as a function of time. So far, this technique has been applied to direct measurement of electron relaxation by electron-phonon scattering in polycrystalline Au[1], hot electron thermalization by e-e scattering in Cu(100)[2], and image potential state decay on Ag(100) and Ag(111) surfaces[3]. With higher time resolution(<10fs) we have been able to resolve coherent component in hot-electron decay due to optical dephasing from the slower population decay rates of hot-electrons at Cu(100) and Cu(110) surfaces[4]. Here we report the results on Cu(100), Cu(110) and Cu(111) surfaces and compare them with Fermi liquid theory.

© 1996 Optical Society of America