Evidence for Umklapp electron scattering emission from metal photocathodes
This paper presents evidence for a new one-photon emission process in single-crystal Cu(001) and W(111) photocathodes near the photoemission threshold, attributing the phenomenon to momentum-resonant Franck-Condon mechanisms mediated by inelastic Umklapp electron scattering and validating the theory through a combined first-principles simulation and direct one-step band emission model.