Tunable photoemission with harmonics of subpicosecond lasers

Soft x-ray photons, generated by the interaction of intense 610 nm subpicosecond laser pulses with rare gases, are used to carry out tunable angle-resolved photoemission on a number of systems. When the intensity at the focus of the input radiation exceeds ∼1014 W/cm2 significant quantities of harmonic photons at odd multiples of the input 610 nm (2.04 eV) light are produced. To date, harmonics from the 5th (10.2 eV) to the 25th (51 eV) have been generated with fluxes sufficient for generating photoemission spectra. The experimental apparatus for harmonic generation and several experiments demonstrating the applications of this light are described.