No abstract

Energy-resolved two-photon photoemission is modeled in the framework of optical Bloch equations for a three-level system. For pulsed excitation, analytical expressions for the photocurrent have been derived which elucidate numerical solutions. The information that can be extracted from linewidth analysis is demonstrated to depend substantially on the shape of pump and probe pulses. The analysis is applied to image-potential states leading to overall good agreement.

In a recent paper (LAUTERBORN, REFSDAL, WEIGERT, 1971) the central He burning phase of 5 M⊙ stars was investigated. It was shown that the structure of such stars is very sensitive to the chemical profile in and above the hydrogen burning shell. The loops in the H-R diagram which such stars often make were for instance found to be very sensitive to changes in this profile. It was also shown that an assumed mass loss of about 10% in the red giant region will suppress a loop completely.

The dynamics of image-potential states on Cu(119) have been studied with two-photon photoemission. Direction-dependent quasielastic scattering processes with large momentum transfer are attributed to the finite terrace-width distribution on the stepped surface. This effectively couples image-potential states via interband scattering and leads to an asymmetry of the decay rate. Electrons in the first image-potential state live apparently longer when running upstairs.

No abstract