An undulator radiation source using a compact electron storage ring wa
s developed for photo-excited processes. Quasi-monochromatic radiation
has been available and the wavelength of the radiation is tunable fro
m 65 to 1000 nm. The full width at half maxima (FWHM) was measured by
a Seya-Namioka type monochromator and the photon fluence was measured
using an ionization chamber. We present here an intense vacuum ultravi
olet light source which emits a photon fluence exceeding 10(15) photon
s/s.