Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
Search results
19 records were found.
Comment: 5 pages, 1 figure, technical report (a software overview)
Linear and nonlinear optical properties in oxide and chalcogenide glasses have been studied comparatively. Applying a semiconductor concept to these glasses, we show that maximal nonlinear refractive-index at optical communication wavelengths is ∼10−4 cm2/GW, which can be obtained in materials with bandgap energy of ∼1.6 eV. It is also shown for SiO2 and As2S3 that linear and nonlinear optical excitations induce different photostructural changes, which are attributable to different photo-electronic transition probabilities.
Nonlinear optical properties of Se-loaded ZSM-5 single crystals have been studied comparatively with those of glassy Se. Two-photon absorption coefficients and intensity-dependent refractive-index of the Se-zeolite are higher by three orders of magnitude than those of glassy Se. The enhancements can be ascribed to electron confinement in single Se chains. © 2009 American Institute of Physics.
Photoinduced phenomena in Se-loaded ZSM-5 single crystals have been studied through electron-spin resonance, optical absorption, and photoluminescence spectroscopy. Marked exposure effects appear at room temperature. Upon illumination of visible light, an electron-spin signal at g [approximate to] 2.00 increases by an order, subgap absorption of 10^3 cm^[-1] appears, and photoluminescence at subgap regions weakens to a half. Timescales of these photoinduced changes including recoveries are not the same, which suggests different origins for the three changes. The spin increase evinces bond scission in single Se chains. © 2009 American Institute of Physics
Comment: 5 pages, 1 figure; v2: minor revisions, also an analytical proof has
been added; v3: to appear in Phys. Rev. A, a theorem added
Comment: 5 pages, 1 figure, RevTex4, v2 minor grammatical changes, typos
corrected
Atomic structures of Se clusters impregnated into ZSM-5 single crystals have been investigated through structural and optical experiments. Raman-scattering spectroscopy suggests that Se in the zeolite takes single chain structures. X-ray diffraction implies that the chains form fourfold (not threefold as in trigonal Se) helices. The chain length is estimated from weight and electron-spin resonance measurements at 10^2 atoms. The material shows an optical absorption edge at hω [similar or equal to] 2.2 eV, which accompanies dichroism, suggesting chain alignment in the zeolite pores. © 2009 American Institute of Physics.
Comment: 14 pages, 18 figures, RevTeX4, v2,v3: typos corrected, v4: minor
changes in PROGRAM 1, conforming it to the actual programs used in the
simulation, v5: correction of a typographical error in the inequality sign in
PROGRAM 1, v6: this version contains a new section on classical correlations,
v7: correction of a wrong use of terminology, v8: Appendix A has been added,
v9: published in PRA
Sulfur, selenium, and tellurium were loaded into sub-mm size ZSM-5 single crystals and the optical properties have been comparatively studied. S and Te show similar features, while Se is unique. S and Te have optical absorption edges at wavelengths of ～400 nm with transmission dips at ～450 nm, while Se has the edge at ～550 nm. The three materials provide photoluminescence at visible wavelengths, with intensities of S and Te being stronger than that of Se by two orders. These optical properties imply that S and Te in the zeolite form small atomic units such as S3 and Te2, while Se condenses into single-chain structures.
Comment: 10 pages, no figure, v1: 6 pages, v2: 13 pages, minor revision, style
changed, proofs in Section 4 changed, v3: minor revision, Remark 2 added, to
appear in QIC
