Optical properties, spectroscopy luminescence

The luminescence of diamonds is related to various defects in its structure. Almost always, luminescence centers in diamonds are related to N atoms. It is logical, because the atomic radii of C and N are nearly equal (approximately 0.77 A). Luminescence spectroscopy has proven to be the most widely used method in studies of diamonds even in comparison with optical absorption, ESR, IR and Raman spectroscopies. Himdreds of spectra have been obtained, fluorescence characteristics enter into diamond quality gemological certificates, a wide range of electronic and laser applications are based on diamond optical properties in excited states nitrogen center aggregation is controlled by the residence time of diamond in the mantle, distinction between natural... 

To characterize the optical properties of the rods obtained, the material was studied by means of PL spectroscopy. When excited with 240 nm uv radiation, the samples exhibit two bands centered at 394 and 486 nm, or, when converted to photon energy, 3.15 and 2.55 eV, respectively, and are due to oxygen vacancies [10]. The enhanced green luminescence from nanorods suggests their applicability in optoelectronic devices. 

The aim of this chapter is to give an overview of how and where ionic liquids have been and are used in optical spectroscopy. Optical properties of prominent ionic liquids themselves will be presented and then their application as solvents for UV-Vis and luminescence spectroscopy will be discussed. However, special care has to be taken to ensure that the ionic liquids used are optically pure. As the optical determination of ionic liquid acidity is one of the most important applications of optical spectroscopy in and of ionic liquids, a whole chapter has been dedicated to this topic. To limit the length of this overview neither mixtures of ionic liquids nor mixtures of ionic liquids with other solvents are discussed. Available literature published until fall of 2008 has been taken into account. 

The shapes of the interatomic potential curves are approximations chosen for mathematical convenience. Such potential functions are generally used in discussions on a variety of properties of molecules and lattices optical absorption and luminescence, laser action, infrared spectroscopy, melting, thermal expansion coefficients, surface chemistry, shock wave processes, compressibility, hardness, physisorption and chemisorption rates, electrostriction, and piezoelectricity. The lattice energies and the vibration frequencies of ionic solids are well accounted for by such potentials. On heating, the atoms acquire a higher vibrational energy and an increasing vibrational amplitude until their amplitude is 10-15% of the interatomic distance, at which point the solid melts. 

Within materials science, the optical properties of ICP-CNT composites refer specifically to the absorption, photo luminescence, Raman and FTIR spectroscopy of ICP-CNT composites. Spectroscopic methods offer the possibiUty of quick and nondestructive characterization of relatively large amounts of ICP-CNT composites. There is a strong demand for such characterization from the industrial point... 

The rare-earth ions with electron configuration 4f show a very characteristic spectroscopy due to the fact that the 4f shell is well shielded from the surroundings. This is also more or less true for the transthorium ions (5f ). These electronic configurations yield optical properties which cannot be observed for other metal ions. These, in turn, lead to many important applications, for lasers, cathode-ray tubes, luminescent lamps and X-ray imaging. 

See also Biomacromolecular Applications of Circular Dichroism and ORD Chiroptical Spectroscopy, Emission Theory Chiroptical Spectroscopy, General Theory Chiroptical Spectroscopy, Oriented Molecules and Anisotropic Systems Circularly Polarized Luminescence and Fluorescence Detected Circular Dichroism Light Sources and Optics Luminescence, Theory Nonlinear Optical Properties Vibrational CD Spectrometers Vibrational CD, Applications Vibrational CD, Theory. 

Figure 2 illustrates the basic concept of a typical pump-probe spectroscopy used in most ultrafast spectroscopy techniques. In its simplest form the output pulse train of an ultrafast laser is divided in two by a beam splitter. One pulse in train (called pump) first excites the sample under investigation. The second pulse train (called probe) will probe the sample with a suitable time delay with respect to the pump by introducing an optical delay in its path and some optical property (e.g., reflectivity, absorption, Raman scattering, luminescence, optical nonlinear responses) of the sample is then detected to investigate the changes produced by the pump. In most of the time-resolved pump-probe experiments, the time resolution is limited only by the pulse width of the laser or the jitter between the laser systems. 

In this paper we will describe and discuss the metal-to-metal charge-transfer transitions as observed in optical spectroscopy. Their spectroscopic properties are of large importance with regard to photoredox processes [1-4], However, these transitions are also responsible for the color of many inorganic compounds and minerals [5, 6], for different types of processes in semiconductors [7], and for the presence or absence of certain luminescence processes [8]. 

---