ANNUAL REPORT 2011 - Instituto de Estructura de la Materia

towards potential optical metamaterials designed on the basis of the physics underlying our doubly-resonant metalodielectricconfiguration. These physical principles can of course be exploited at lower (far-IR and terahertz)frequencies, at which some dielectric materials exhibit very large refractive indices and certain materials (e.g. polarcrystals, doped semiconductors) behave as plasmonic metals. Finally, it should be emphasized that the requiredfabrication means will open a novel route towards the nanosynthesis of NIM.Schematic representation of the physics behind the core-shell configuration. The strong diamagnetic response is dueto the lowest, dipolar magnetic resonance in the shell, where the electric field is forced to rotate as a consequence ofthe abrupt continuity conditions for the normal component between the shell and the surrounding medium. Theelectric resonance is a LSPR in the metal core.LASER INDUCED BREAKDOWN SPECTROSCOPY (LIBS)We have studied the Laser Induced Breakdown Spectroscopy of CO 2 at different pressures by using high resolutionOptical Emission Spectroscopy. The strong emission of the CO 2 plasma shows excited neutral O and C atoms andionized O + and C + species. The medium-weak emission is due to electronic relaxation of excited species C 2+ , O 2+ ,N + , N, H and molecular band systems of C 2 , CN, O 2 , O + 2 , N 2 and N 2+ . Threshold intensities, plasma temperature andvelocity distributions for different species were obtained. Electron density in the laser-induced plasma was estimatedand from the TOF profiles for distinct species the corresponding three-body electron–ion recombination rateconstants were obtained. The laser-induced breakdown spectroscopy of He at several pressures has been studied.The helium breakdown spectrum is mainly due to electronic relaxation of excited He, He + and H. Plasmacharacteristics were examined by the time-integrated and time resolved optical emission spectroscopy. Opticalbreakdown threshold intensities, ionization degree and plasma temperatures were obtained. The velocity and kineticenergy distributions for He and He + species were obtained from time-of-flight measurements. Electron density andits temporal evolution have been used for the estimation of the three-body electron–ion recombination rate constant.A review of some fundamentals of LIBS and some experimental studies developed in our laboratory on gases suchas nitrogen, oxygen and air has been done as a book chapter. The physical processes leading to laser-inducedbreakdown of gases have been analyzed. Optical breakdown threshold intensities in different gases have beenexperimentally measured. Excitation temperatures and electron number densities are estimated from the intensitiesand the Stark broadening of several ionic lines. The velocity and kinetic energy distributions for the different specieswere obtained from time-of-flight (TOF) OES measurements. Temporal evolution of electron density has been usedfor the estimation of the three-body recombination rate constant. The previous results of LIBS in different samples(He, Ge, GeH 4 and CO 2 ) have been reviewed for the publication of a book chapter. These works have been done incollaboration with Profs. J.J. Camacho and J.M. Poyato (Phisical-Chemistry Department of UAM).INFRARED LASER INDUCED ABLATION PLASMASIR CO2 Laser Induced Ablation of graphite target has been studied. Analyzes with spatial and temporal resolutionfor the plasma plume were done. Wavelength-dispersed spectra of the plume reveal the emission of C, C + , C 2+ , C 3+ ,C 4+ , N, H, O, N + , O+ and molecular features of C 2 , CN, OH, CH, N 2 and NH. Excitation, vibrational and rotationaltemperatures, ionization degree and electron number density for some species were estimated. This work has beenpublished as a book. Time-resolved optical emission spectroscopy has been applied in the laser-induced ablationplumes of germanium targets. The temporal behavior of Ge atoms and ionized excited species Ge3+, Ge2+, and Ge+have been studied. The velocity distributions and the three-body electron-ion recombination rate constants for these65