One‐photon two‐electron transitions at surfaces

Sensing the electron–electron correlation in solids via double photoemission

“…5 indicate that in Ni the internal (e,2e) process is more dominant compared to the observation for Cu(100). A theoretical explanation connects these difference to the higher density of states at E F for Ni compared to Cu [20].…”

“…In general two possible pathways for pair emission exist [19,20]. On one hand, a single photon can be absorbed, which is accompanied by the emission of an electron pair.…”

Overview of core and valence photoemission

“…The photoemission process in its original concept is viewed as a single-particle probetwo-electron photoemission has been studied only recently (as described in two chapters [30,36] of this volume). A single electron is removed from its binding environment and its spectral and angular distributions are recorded outside the material.…”

“…Theoretical investigations have culminated in the quantitative evaluation of the GW-approximation now most common to bandstructure calculations. [37,59] Strongly correlated systems present another challenging problem of many-body physics [60] where spectroscopy has opened a new branch with two-electron photoemission, see [36].…”

Electron pair emission from a W(001) surface: photon versus electron excitation

“…Recent development in laser technology have shown that attosecond light pulses can be generated [13], which may allow us in the future to separate the two pathways directly. It is expected that both scenarios make comparable contributions to the total (γ , 2e) intensity, because in both cases the underlying interactions, namely electronelectron and electron-photon interactions, appear in the same order [14]. In coincidence experiments one has to operate at low primary fluxes in order to reduce the contributions of socalled random coincidences.…”