Development of a UV-laser Based Ultra-High Resolution Angle-Resolved Photoemission Capability for Electronic Structure Studies

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9704045 Dessau A state-of-the-art high resolution photoemission capability will be developed at the University of Colorado with support from The Division of Materials Research and The Office of Multidisciplinary Activities. A novel and particularly powerful aspect of the instrumentation will be the development and usage of a high power femtosecond UV laser system as an excitation source for photoemission experiments of electronic materials. The UV-laser system will provide: (1) a photon flux orders of magnitude higher than is achievable by other means, including the best wiggler or undulator sources at a synchrotron. (2) Very high energy resolution (1-10 meV), depending upon the temporal length of the pulses. (3) Greater ease in controlling the photon polarization (linear, circular, etc.), which is very helpful for obtaining the symmetry of the electronic states. (4) Much greater bulk sensitivity because the electron mean free paths get very long at low kinetic energies. For studies of the bulk electronic structure, this will overcome one of the major difficulties of photoemission today, and open up the technique to the study of many materials systems which have not to date yielded high enough quality surfaces for reliable photoemission experiments. (5) Pump-Probe based photoemission which will enable us to (a) Study the unoccupied levels near the Fermi energy. This may replace inverse photoemission as the too of choice for this purpose, as inverse photoemission suffers from poor resolution (a few tenths of an eV), low count rates, and is damaging to a sample surface. (b) Study the dynamics of the system by varying the delay between the pump and the probe beams. The system will make use of the most advanced electron spectroscopic and laser instrumentation. To our knowledge, this powerful combination does not currently exist anywhere in the world. The requested instrumentation will also fill a hole in the techniques available in the greater Boulder area, and will be available to the local scientific community. ***