Abstract:
We report rst results from our e ort to couple a high resolution photoemission electron microscope
(PEEM) to the OK-4 ultraviolet free electron laser at Duke University (OK-4 /Duke UV FEL). The
OK-4 /Duke UV FEL is a high intensity source of tunable monochromatic photons in the 3{10 eV
energy range. This tunability is unique and allows us to operate near the photoemission threshold of
any samples and thus maximize sample contrast while keeping chromatic aberrations in the PEEM
minimal. We have recorded rst images from a variety of samples using spontaneous radiation from
the OK-4 /Duke UV FEL in the photon energy range of 4.0{6.5 eV. Due to di erent photothreshold
emission from di erent sample areas, emission from these areas could be turned on (or o ) selectively.
We have also observed relative intensity reversal with changes in photon energy which are interpreted
as density-of-state contrast. Usable image quality has been achieved, even though the output power of
the FEL in spontaneous emission mode was several orders of magnitude lower than the anticipated full
laser power. The PEEM has achieved a spatial resolution of 12 nm.
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