Femtosecond energy transfer between chromophores in allophycocyanin trimers

Ultrafast energy-transfer processes in allophycocyanin (APC) trimers from Mastigocladus laminosus have been examined by a femtosecond absorption technique. Isotropic absorption recovery kinetics with τ=440±30 fs were observed in APC trimers at 615 nm. In APC monomers such a fast process was not observed. The anisotropy in both samples was constant and close to 0.4 during the first few picoseconds. The results are consistent with a model of the APC trimer in which the two APC chromophores have different absorption spectra with maxima about 600 and 650 nm. The transfer of energy from the 600 nm chromophore to the 650 nm chromophore occurs in 440 fs and is dominated by the Förster dipole—dipole energy-transfer mechanism

High energy density physics with intense ion and laser beams

We will present the status and perspectives of High Energy Density Physics (HEDP) with intense heavy ion beams as a tool to induce extreme states of matter..

CERN PS laser ion source development

CERN, together with ITEP and TRINITI (Russia), is developing a CO2 laser ion source. The key design parameters are: 1.4 1010 ions of Pb25+ in a pulse of 5.5 ms, with a 4-rms emittance of 0.2 10-6 rad m, working at a repetition rate of 1 Hz. This device is considered as one candidate source for LHC heavy ion operation. The status of the laser development, the experimental set-up of the source consisting of the target area and its illumination, the plasma expansion area and extraction, beam transport and ion pre-acceleration by an RFQ, will be given

Growth of SiC films by the method of substitution of atoms on porous Si (100) and (111) substrates

The mechanisms of growth of silicon carbide (SiC) films by the method of substitution of atoms on macro- and mesoporous silicon substrates (Si) of p- and n-type conduction are investigated. Significant dependence of the rate and the mechanism of nucleation of SiC layers on Si on the type of Si doping and its crystallographic orientation is experimentally found. Comparison of the experimental data with the theoretical results obtained earlier is performed. It is shown that the presence of the system of pores on the surface allows one to significantly increase the thickness of silicon transformed into SiC during the process of synthesis by the method of substitution of atoms, which was equal to 115 microns in our experiments. The obtained samples are studied by methods of scanning electron microscopy, micro-Raman spectroscopy, and X-ray diffraction analysis. Numerical simulation of the distribution of elastic stresses caused by the difference in thermal expansion coefficients (TEC) in the heterostructures of GaN/SiC/porous Si/Si is conducted. It is revealed that the presence of pores in the near-surface layers of Si leads to considerable relaxation of elastic stresses in GaN films caused by differences in the TEC between GaN and Si