Multi-µJ coherent extreme ultraviolet source generated from carbon using the plasma harmonic method.
We demonstrate intense high-order harmonic generation from plasma that is created from different carbon targets. We obtain high-order harmonic energy in the multi-microjoule range for each harmonic order from the 11th to the 17th harmonic. By analyzing the target morphology and the plasma composition, we conclude that the intense harmonics from the bulk carbon targets originate from nanoparticles target.
Strong resonance enhancement of a single harmonic generated in the extreme ultraviolet range.
We report the demonstration of strong resonance enhancement of a single high-order harmonic in the extreme ultraviolet (XUV) region generated from the interaction of a femtosecond pulse with low-ionized In ablation. A strong 13th harmonic (61.2 nm) of Ti:sapphire laser radiation with output intensity almost two orders of magnitude higher than neighboring harmonics was observed in these studies. The high conversion efficiency of the 13th harmonic (8 x 10(-5)) is attributed to multiple collisions of electron trajectories with the origin due to multiphoton resonance with the In ion.
Single-particle and collective degrees of freedom in C60
The electromagnetic response of the fullerene C60 in the energy range 0<or=E<or=35 eV, exhausting 84% of the Thomas-Reiche-Kuhn sum rule, has been worked out using the local density and random phase approximations. A detailed correspondence between the calculated pi -plasmons and the peaks determined in optical/UV studies is found. The damping width ( approximately=12 eV) of the Mie resonance observed at approximately=20 eV is well reproduced, and is due to Landau damping. This resonance is found to be determined by sigma to sigma and, to a large extent, also by sigma to pi , delta particle-hole transitions.