I. S. GORBAN et al. The photoluminescence (PL) spectra of the monoclinic modification of the semiconductor crystal ZnP, (P-ZnP,) are studied under high, intermediate, and low laser excitation intensities at liquid helium temperature. Under high excitation intensities the inverse hydrogenlike M-series was observed. It is symmetrical with the hydrogen-like excitonic series. This M-series is due to the two-electron transitions from the excitonic molecule (biexciton) state to the ground, excited, and ionized excitonic states. The binding energy of the biexciton in O-ZnP, is determined as dbex = 14.9 meV (0.32 of exciton Rydberg). Under intermediate excitation intensities another G-band appears in the PL spectrum of P-ZnP,. This band is interpreted as a result of two-photon annihilation of free excitonic molecules in the gas phase. A narrow C-line appears in the PL spectrum under intermediate excitation intensities, too. The analysis of the temperature dependence of the C-line intensity allows us to assume this line to be the result of two-photon annihilation of the biexcitons condensed into a dielectric liquid with the binding energy A , zz 0.5 meV.

In the present work, we used Raman spectroscopy as sensitive tool for characterization of dispersion of electron-phonon resonances in one-layer graphene. We analyzed Stokes and anti-Stokes components of the Raman spectra to investigate the temperature dependence of the graphene G-band on the power of exciting radiation. Appearance and drastic intensity increase of zone-edge D-like modes caused by introduction of structural defects and/or deformations in the graphene layer were observed in the Raman spectra at high powers of excitation. We investigated phonon dispersion of one-layer graphene for iTO phonon branch at K point along K-M direction, which is involved in double-resonance Raman scattering. Raman dispersion slope of D-band is in good agreement with results of theoretical calculations based on the Green's functions approach based on the screened electron-electron interaction. Deviation of the experimental iTO phonon frequency from the linear dependence on excitation energy was observed at excitation E(exc) = 3.81 eV. Self-consistent classification of phonon states according to the symmetry for all dispersion branches of one-layer graphene was carried out.

A simple method for producing unsupported nickel catalyst that can be used to synthesize multi-wall carbon nanotubes (MWNT) has been developed. The yield of purified MWNTs is about 1.8 g MWNT /(g cat ×h).

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