A high-order harmonic generation apparatus for time- and angle-resolved photoelectron spectroscopy

Abstract

We present a table top setup for time-and angle-resolved photoelectron spectroscopy (tr-ARPES) to investigate band structure dynamics of correlated materials driven far from equilibrium by femtosecond laser pulse excitation. With the electron-phonon equilibration time being in the order of one to two picoseconds it is necessary to achieve sub-picosecond time resolution. Few techniques provide both the necessary time and energy resolution to map non-equilibrium states of the band structure.Laser-driven high-order harmonic generation is such a technique. In our experiment a grating monochromator delivers tunable photon energies up to 40 eV. A photon energy bandwidth of 150 meV and a pulse duration of 100 fs FWHM allow us to cover the k-space necessary to map valence bands at different k z and detect outer core states.

Intervalley scattering in MoS2 imaged by two-photon photoemission with a high-harmonic probe

“…First angle-resolved 2PPE experiments with high-harmonic probe studied collective phenomena after strong excitations in the occupied band structures such as phase transitions in charge-density wave materials and magnetic systems [22][23][24] or hot electron dynamics close to the Fermi level E F as in graphene [25,26]. In these experiments, the specific photon energy of the excitation played a minor role.…”

Probing photoelectron angular distributions in molecules with polarization-controlled two-color above-threshold ionization

“…They are expressed in the spectra as satellite lines shifted in kinetic energy with respect to the main line from single-photon VUV ionization by the energy of one or more IR photons. As the sideband intensity represents a cross-correlation signal of the femtosecond IR and VUV pulses, two-photon TCATI on gaseous as well as solid samples has ever since been used to determine the temporal resolution in pump-probe photoelectron spectroscopy experiments with laboratory VUV and soft x-ray sources and free-electron lasers (FELs) [5][6][7][8][9][10][11][12][13][14][15][16][17].In TCATI in atoms it was discovered that the sideband intensity depends on the relative orientations of the linear polarization vectors of IR and VUV radiation [18,19]. This effect was then used in polarization-controlled TCATI to extract the angular distribution and the symmetry of the outgoing TCATI electron waves in He as a function of the dressing photon field density [20].…”

A table-top monochromator for tunable femtosecond XUV pulses generated in a semi-infinite gas cell: Experiment and simulations

“…[7][8][9][10]12 It has to be acknowledged that the values we give here are on the lower edge of this range, particularly compared to Ref.…”

“…Structurally simple and theoretically accessible systems have been measured in the most meticulous detail, with a recent shift of the focus towards ever more complex objects of interest. With the advent of sufficiently short XUV pulses [4][5][6][7][8][9][10][11][12][13] , dynamical effects can be examined directly in the time domain revealing new insights into the quantum-mechanical foundations of chemistry and physics. For example time-and angle-resolved photoelectron spectra can be measured providing access to individual partial-wave contributions and their relative phase shifts [14][15][16][17] .…”