We present our latest results on the generation of ultrashort vacuum UV (VUV) pulses by nonresonant four-wave mixing of chirped broadband pulses generated by filamentation of the fundamental of a Ti:sapphire laser with relatively narrowband pulses at the third harmonic. Positive chirp at the broadband idler yields negatively chirped VUV pulses necessary to compensate for material dispersion of a Mg F 2 window in the VUV beam path. Pulse energies exceeding 400 nJ are available for time-resolved experiments. Pulse duration is measured by pump–probe ionization of Xe gas, providing the cross correlation between the fifth harmonic and the fundamental
