A two-photon photoemission study of spin-dependent electron dynamics

We describe a spin- and femtosecond time-resolved two-photon photoemission experiment with an overall energy resolution of 90 meV and an angular resolution of ±2.5° at an electron count rate of a few kHz. As a model system we have studied image-potential states in front of a three monolayer iron film on Cu(1 0 0). With our setup an exchange splitting of both, the n = 1 and n = 2 image-potential state is clearly discernible. A strong dependence of the spin polarization in the image-potential states on the polarization of the pump light can be observed. Time-resolved measurements reveal that the lifetime of excited majority-spin electrons exceeds that of minority-spin electrons by a factor of 1.4.