RESUMO
The Cooper minimum (CM) has been studied using high harmonic generation solely in atoms. Here, we present detailed experimental and theoretical studies on the CM in molecules probed by high harmonic generation using a range of near-infrared light pulses from λ=1.3 to 1.8 µm. We demonstrate the CM to occur in CS(2) and CCl(4) at ~42 and ~40 eV, respectively, by comparing the high harmonic spectra with the known partial photoionization cross sections of different molecular orbitals, confirmed by theoretical calculations of harmonic spectra. We use CM to probe electron localization in Cl-containing molecules (CCl(4), CH(2)Cl(2), and trans-C(2)H(2)Cl(2)) and show that the position of the minimum is influenced by the molecular environment.
RESUMO
We demonstrate high-harmonic generation in H(2)O using 800 and 1300 nm laser pulses up to a maximum intensity of 5x10(14) W/cm(2). Under optimal phase-matching conditions, photon energies up to approximately 60 and approximately 87 eV are produced by using 800 and 1300 nm light, respectively. The harmonic spectra in H(2)O, when compared with Xe with a similar ionization potential, exhibit significant extension of the cutoff region, indicating suppression of ionization arising from molecular orbital symmetry.
RESUMO
We demonstrate, for the first time, high-order harmonic generation from C60 by an intense femtosecond Ti:sapphire laser. Laser-produced plasmas from C60-rich epoxy and C60 films were used as the nonlinear media. Harmonics up to the 19th order were observed. The harmonic yield from fullerene-rich plasma is about 25 times larger compared with those produced from a bulk carbon target. Structural studies of plasma debris confirm the presence and integrity of fullerenes within the plasma plume, indicating fullerenes as the source of high-order harmonics.
