High Rydberg states of the krypton atom have been investigated at high reso
lution by vacuum ultraviolet-millimeter wave double-resonance spectroscopy.
The measurement of Stark shifts in the spectra of these high Rydberg state
s is used to determine electric fields with a +/-20 mu V/cm accuracy. The a
nalysis of spectral line shapes provides information on inhomogeneous elect
ric field distributions in the experimental volume. [S0031-9007(99)08605-6]
.