Optical absorption and emission spectra

Broad bands in optical absorption and emission spectra originating from one or several closely lying electronic transitions are indications of strong vibronic coupling. In the case when the vibrational structure is resolved into a progression of individual bands, a vibronic analysis can be carried out which compares a theoretical line shape function with the intensity profile measured in the... 

Another nonreactive route to the characterization of solvent polarity is the study of the optical absorption and emission spectra of chromophores [188]. These spectra are sensitive to the molecular environment, and because different solvatochromic probes may have different capacities for specific interactions, it is possible to characterize the solvent environment in detail and to construct LFERs analogous to those described above. Studies of the spectra of solvatochromic probes in ionic liquids have in general been consistent with the results of partitioning studies described above [8-10, 69, 70, 198-200], though we will discuss one observed anomaly below [198]. 

From measurements of the optical absorption and emission spectra as a function of temperature, the energy separation Ej- Ee (in cm ) is 2350 - 0.91 T, with the latter factor accounting for the relative shifts of the E and T states as the lattice expands with increasing temperature. The relative populations are thus given by... 

The main features of the optical absorption and emission spectra of transition metal complexes can be interpreted on the basis of crystal-field or ligand-field theory. Generally, the energies of the absorption and the emission bands correspond to energetic differences between electronic states. Therefore, an interpretation of the optical spectra will start with a comparison between the experimental spectra and the term diagram of the complex ion, according to the crystal-field theory. This procedure will be demonstrated by two informative examples. 

The mechanism to detect pinacolyl methylphosphonate is to discern its effect of the luminescence of a lanthanide ion, Eu (5). The optical absorption and emission spectra of the triply charged free lanthanide ions, which are assignable to f->f transitions, generally consist of very narrow lines (0.1-0.01 nm). Organic compounds with affinity to form metal ion complexes are called... 

A few papers deal with KNIgEsrEu " " phosphors. Two of them, by Furetta et al. (1990) and Bacci et al. (1993), both from the same laboratory, stress the good dosimetric properties of the above phosphor. The RT y- and 3-irradiated samples exhibited a prominent TL peak at 613 K. Its sensitivity remained constant over the range of 4x 10 -1 sv. It exceeded the sensitivity of TLD-700 discs by a factor of nearly three and that of LiF Mg,Ti pellets by a factor of five. Its fading is described to be negligible and it is claimed to show no interfering effects. In the 1993 paper the authors studied the optical absorption and emission spectra. From this they concluded that in spite of the introduction of Eu as three-valent EuBrs, only Eu was incorporated in the host material. The high-temperature TL peak was found to shift to lower temperatures and to increase in intensity with the concentration of the Eu dopant. 

Goldberg A, McClure D, Pedrini C (1982) Optical-absorption and emission-spectra of Cu+, NaF single-crystals. Chem Phys Lett 87 508-511... 

The optical absorption and emission spectra of conjugated polymers and oligomers have been reviewed. The optical bandgaps of the conjugated polymers that are organic semiconductors range from 1 to 3.5 eV. The photoluminescence spectra of conjugated... 

One interesting new field in the area of optical spectroscopy is near-field scaiming optical microscopy, a teclmique that allows for the imaging of surfaces down to sub-micron resolution and for the detection and characterization of single molecules [, M]- Wlien applied to the study of surfaces, this approach is capable of identifying individual adsorbates, as in the case of oxazine molecules dispersed on a polymer film, illustrated in figure Bl.22,11 [82], Absorption and emission spectra of individual molecules can be obtamed with this teclmique as well, and time-dependent measurements can be used to follow the dynamics of surface processes. 

F ure 6.9 The absorption and emission spectra of ruby (Al203 Cr ). On the left-hand side, the energy levels of Cr in AI2O3 are shown for a proper assignment of the observed optical bands. 

Figure 2. Optical absorption and emission (inset) spectra of 1 in butyronitrile.

The optical properties of the 8-o-PhOH-purine adducts have provided insight into their ground-state structures at the nucleoside level. These adducts have the ability to phototautomerize, through an excited-state intramolecular proton transfer (ESIPT) process, to generate the keto form. This tautomerization depends on the presence of a intramolecular hydrogen (H)-bond between the phenolic OH and the imine nitrogen (N-7). Figure 14 shows normalized absorption and emission spectra for 8-o-PhOH-dG and 8-o-PhOH-dA in aqueous buffered water and hexane. In water, 8-o-PhOH-dG shows only enol emission at 395 nm, while 8-o-PhOH-dA shows enol emission at 374 nm and phenolate emission at 447 nm. In hexane, both adducts show keto emission at 475 nm 8-o-PhOH-dA also shows a small amount of enol emission and no phenolate emission. These results show that in water, the intramolecular H-bond... 

Considerable attention has been paid in the past few years to the study of both the absorption and emission spectra of the rare earths. This has been boosted further by the development of the new branch of physics, the Laser (light amplification through stimulated emission of radiation). The study of the optical spectra of ions yields valuable information about the energy levels of normal configurations and of excited states, and also about the nature of their environment. However, a detailed analysis of optical spectra demands a considerable knowledge of theoretical techniques. Recent advances in paramagnetic resonance techniques [479] have enabled us to understand the nature of the ground states of the rare earth ions in crystalline environments. 

The P coordination to the AuCl salt induces more pronounced effects on the optical properties, that is, the larger bathochromic shifts in absorption and emission spectra (A ,abs = 25-52 nm A ,em = 24-66 nm) and a considerable decrease in emission efficiency. 

Optical absorption and fluorescence spectra of 636-655 were measured both in solution and as thin films to assess the effect of both fluoroalkyl-versus alkyl- and a,co- vs ( , ( -substitutions on oligothiophene absorption and emission maxima (Xabs/Am) and the (optical) HOMO-LUMO energy gaP-... 

In this paper we present a comprehensive first-principles study of the structural, electronic and optical properties of undoped and doped Si nanosystems. The aim is to investigate, in a systematic way, their structural, electronic and stability properties as a function of dimensionality and size, as well as pointing out the main changes induced by the nanostructure excitation. A comparison between the results obtained using different Density Functional Theory based methods will be presented. We will report results concerning two-dimensional, one-dimensional and zero-dimensional systems. In particular the absorption and emission spectra and the effects induced by the creation of an electron-hole pair are calculated and discussed in detail, including many-body effects. 

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