  We report on the generation of intense extreme ultraviolet (EUV)
supercontinuum with photon energies spanning from 35 eV to 50 eV (i. e.,
supporting an isolated attosecond pulse with a duration of ~271 as) by loosely
focusing 35 fs, 11 mJ pulses from a femtosecond laser amplifier into a 10-mm
long gas cell filled with krypton gas. The dramatic change of spectral and
temporal properties of the driver pulses after passing through the gas cell
indicates that propagation effects play a significant role in promoting the
generation of the EUV supercontinuum.
