Plasmon-enhanced high order harmonic generation of open-ended finite-sized carbon nanotubes: The effects of incident field's intensity and frequency and the interference between the incident and scattered fields.

The nonlinear optical properties of hybrid systems composed of a silver nanosphere and an open-ended finite-sized armchair single-walled carbon nanotube (SWCNT) are systematically investigated by the hybrid time-dependent Hartree-Fock (TDHF)/finite difference time domain (FDTD) approach, which combines the real-time TDHF approach for the molecular electronic dynamics with the classical computational electrodynamics approach, the FDTD, for solving Maxwell's equations. The high order harmonic generation (HHG) spectra of SWCNTs are studied as a function of the intensity (I0) and frequency (ω0) of the incident field, and SWCNTs length as well. It is found that the near field generated by a Ag nanoparticle has an overall enhancement to the molecular HHG in all the energy range, and it extends the HHG spectra to high energy. The inhomogeneity of the near field results in the appearance of even-order harmonics, and their corresponding spectral intensities are sensitive to ω0, therefore the near field's gradient. When ω0 is far away from the frequency of plasmon resonance of the silver nanosphere (ωc), the interference between the incident and scattering light beams extends the spectral range and makes the HHG spectra more sensitive to I0, while at ω0 = ωc, the impact of the interference on the spectra is negligible.

Towards ultra small noble metal nanoparticles: testing Jellium model for ligand protected copper and silver M13 core nanoparticles.

The bare M and ligand-protected nanoparticles M(25)(SR) and M(13)(PR)(10)Cl (M = Au, Ag, Cu) are investigated using the density functional theory. There are strong interactions between the metal core atoms and the ligands. It is found that the electronic structures agree well with the Jellium model for gold and copper nanoparticles. The superatoms's S and P orbitals are shown. However for silver ones, as the adding of the ligands, the S orbital of the nanoparticle disappears. The binding energy of these nanoparticles are also obtained by our calculation. The Au nanoparticles are most stable, the Cu ones take second place, and the Ag ones are the third stable. Our results could be essential for further understanding of the properties of ligand-protected isolated superatoms.