A novel apparatus devoted to time-resolved photoemission experiments in the sub-picosecond regime will be presented. The system is composed of a Ti:sapphire laser source and a time of flight (TOF) electron energy analyzer mounted in a UHV experimental chamber. The laser source is characterized by a pulse duration of 150 fs at a wavelength of 790 nm (1.57 eV) and operates at a repetition rate of 1 kHz. To perform photoemission measurements, UV radiation up to 6.28 eV is produced with sequential steps of frequency conversion by employing crystals with a second order nonlinearity. Photoelectrons are collected by a TOF spectrometer designed to analyze electrons from tenths of eV up to 5 eV. It can be operated in two dierent angular resolution modes switching on and o an electrostatic collection optics: the high angular resolution mode ( = 2:7 ) and the low angular resolution mode ( = 5:6). Single photon photoemission spectra from the Ag(100) clean surface have been recorded at room temperature using the fourth harmonic light ( = 200 nm and h = 6:28 eV). The Fermi edge prole convoluted with a Gaussian-shaped energy transmission function of the TOF spectrometer sets an upper limit for the energy resolution which is about 65 meV (FWHM) at 2 eV of electron energy.
A novel apparatus for laser-excited time-resolved photoemission spectroscopy
PARMIGIANI, FULVIO;CAUTERO, GIUSEPPE;COMELLI, GIOVANNI;
2002-01-01
Abstract
A novel apparatus devoted to time-resolved photoemission experiments in the sub-picosecond regime will be presented. The system is composed of a Ti:sapphire laser source and a time of flight (TOF) electron energy analyzer mounted in a UHV experimental chamber. The laser source is characterized by a pulse duration of 150 fs at a wavelength of 790 nm (1.57 eV) and operates at a repetition rate of 1 kHz. To perform photoemission measurements, UV radiation up to 6.28 eV is produced with sequential steps of frequency conversion by employing crystals with a second order nonlinearity. Photoelectrons are collected by a TOF spectrometer designed to analyze electrons from tenths of eV up to 5 eV. It can be operated in two dierent angular resolution modes switching on and o an electrostatic collection optics: the high angular resolution mode ( = 2:7 ) and the low angular resolution mode ( = 5:6). Single photon photoemission spectra from the Ag(100) clean surface have been recorded at room temperature using the fourth harmonic light ( = 200 nm and h = 6:28 eV). The Fermi edge prole convoluted with a Gaussian-shaped energy transmission function of the TOF spectrometer sets an upper limit for the energy resolution which is about 65 meV (FWHM) at 2 eV of electron energy.Pubblicazioni consigliate
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