HIGH-ORDER HARMONIC-GENERATION IN MOLECULAR GASES

We present an experimental study of harmonic generation in molecular g ases, using the fundamental (800 nm) and the second harmonic (400 nm) of a 150 fs titanium-sapphire laser at an intensity of similar to 2 x 10(14) W cm(-2). We compare the conversion efficiency and the maximum energy obtained in different species: rare gases (Ar, Xe), diatomic mo lecules (N-2, H-2, O-2, CO) and polyatomic molecules (SF6, N2O, CO2, C H4, C3H8). The harmonic spectra from molecular gases are very similar to those obtained in the atomic gases, with a plateau and a cutoff who se location is strongly correlated to the value of the ionization pote ntial. The conversion efficiency is not higher than that of the rare g ases.