196,197 research outputs found
Optical investigation on dye-doped sol-gel glasses
No full textWe have investigated the optical properties of the 3,3'-diethyloxadicarbocyanine iodide (DODCI) dye incorporated in a number of sol-gel glasses in order to study the interaction between the trapped molecule and the host matrix. The differences found in both the absorption and the photoemission spectra demonstrate that the excitation processes of the dye molecule are influenced by the chemical reactivity and the degree of porosity of the surrounding network. We have found that while the molecular photoisomerization is quenched in all the matrices, for the modifications of the electronic excited states the high rigidity of the purely inorganic silica matrix is required. Conversely, the possibility of chemical attacks to the molecular conjugate chain seems to increase in the hybrid organic/inorganic ormosil matrices. © Societò Italiana di Fisica
Laser excitation and spin coherence of phosphorescent F2+2 centers in CaO
No full textSpin coherence in the laser-excited triplet state of F2+2 centers in CaO is studied. Selective probing of the F+-center local properties is provide by the measurement of the F2+2-center spin-echo decay at different excitation wavelengths. In addition, spin-echo beat phenomena arising at high-power pulsed-laser excitation are reported. © 1984
EXTENSION OF TWO-PHOTON SPECTROSCOPY TO THE VACUUM ULTRAVIOLET USING SYNCHROTRON RADIATION
No full textSynchrotron radiation has been used for the first time in two-photon spectroscopy. The experimental apparatus, built at the ADONE storage ring in Frascati, and using a Q-switched Nd:YAG laser as a powerful source is presented. Space and time superposition of the beams is discussed extensively. Testing of the apparatus has been performed by measuring the two-photon absorption spectra of KCl and NaCl
Refractive index measurements of thin films using both Brewster and m-line technique: A combined experimental setup
No full textApplications of synchrotron radiation in defect and color center research
No full textVUV synchrotron radiation in the energy interval between 4 and 100 eV has been widely used in the study of the optical properties of large gap insulators either pure or doped with various impurities such as heavy metals and rare earths. Besides the absorption and emission properties, important results such as photon multiplication and Auger-free luminescence have been revealed in these investigations. The radiative damage produced in ionic crystals by synchrotron radiation is also discussed, with a brief description of the lattice defects produced and the atom or ion desorption from the irradiated crystals. © 1990
Even-parity excited states of Ag-centers in alkali halides
No full textTwo-photon excitation of the Ag- centers in RbCl, RbBr, and KCl have been measured. From the dependence of luminescence on the polarization of the exciting beams, the symmetry of the final levels could be obtained. In all three host crystals, we observed an intense band assigned to the 1A1g1A1g transition. At higher energies 1A1g1Eg and 1A1g1T2g transitions could be identified but their presence and intensity change in the different crystals. On the high-energy side of the investigated range, we could observe an intense luminescence signal arising from a two-step excitation process; the exciting photon energy becoming resonant with the 3T1u state (A band). © 1991 The American Physical Society
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