We report high harmonic generation from a 248.6-nm KrF laser giving ha
rmonic orders up to the 37th (67 Angstrom) in a helium gas jet and the
35th (71 Angstrom) in neon, for laser intensities up to 4 x 10(17) W/
cm(2) in 380-fs pulses. These observations are interpreted using theor
etical modeling that identifies the ion species He+, Ne+, and Ne2+ as
the sources of the highest harmonics.