Doping electronic spectra

Electronic spectra (Table 1.1, Fig. 1.2) have been measnred for the orange soln-tions of (RuO ] in aqueous base from 250-600 nm. [212-215, 222], and reproduced [215, 222]. There are two at 460 and 385 nm. [212, 213, 222] or three bands in the visible-UV region, at 460, 385 and 317 nm [214, 215]. These appear to be at the same positions as those for [RuO ] but the intensities and hence the general outline of the two spectra are very different. Woodhead and Fletcher reviewed the published molar extinction coefficients and their optimum values / dm (mol" cm" ) are 1710 for the 460 nm. band, 831 for the 385 nm. band and 301 for the 317 nm. band - the latter band was not observed by some workers [214]. The distinctive electronic spectrum of ruthenate in solution is useful for distinguishing between it, [RuO ]" and RuO [212, 222]. Measurements of the electronic spectra of potassium ruthenate doped in K CrO and K SeO and of barium ruthenate doped into BaSO, BaCrO, and BaSeO (in all cases the anions of these host materials are tetrahedral) indicate that in that these environments at least the Ru is tetrahedrally coordinated. Based on this evidence it has been suggested that [RuO ] in aqueous solution is tetrahedral [RuO ] rather than franx-[Ru(0H)3(0)3] [533, 535]. Potential modulated reflectance spectroscopy (PMRS) was used to identify [RuO ] and [RuO ] " in alkaline aqueous solutions during anodic oxidation of Ru electrodeposited on platinum from [Ru3(N)Clg(H30)3] [228]. 

Concerning the cuprates it is now clear that a nonrigid basic electron spectrum must be used. Doping creates not only carriers but prepares the whole background (incorporating also structural changes) for the appearance of superconductivity. Under corresponding approaches there are ones which take as the basis a narrow defect (bipolaron) band above the itinerant band [23,40-48], or stripe-induced minibands [11,42],... 

The underlying cuprate electron spectrum incorporates the itinerant valence band (b) covering energies from —D to zero with the weight of 1 — c. The doping-created band (a) distributes its width from d to d — ac with the weight c. 

Ab Initio Model Potential Calculations on the Electronic Spectrum of Ni2+-Doped MgO Including Correlation, Spin-Orbit and Embedding Effects. 

The simplest method of improving resolution in an electronic spectrum is decreasing the temperature. One of the main advantages of low temperature is that thermal population of excited vibrational states is decreased and the spectrum is simplified. A dramatic example of the effect of decreasing the temperature on an emission spectrum is discussed in Sections IV.A and V.A.2. A second method of improving resolution is doping in a matrix. For example, a metal ion such as Cr can be doped in an ionic lattice such as elpasolite [30,31]. The low concentration of ions in well-defined crystal lattice sites can... 

The infrared spectrum of the, as yet, unidentified excited electronic state has been recorded, and shows a pattern very similar to the doping-induced spectrum. Vj and V2 modes are almost superimposable in the doped and photoexcited material, V3 occurs at frequencies lower that the corresponding doping-induced mode, and is isotope-dependent [42]. Photoexcitation of "trans in cis" PA shows extra small peaks, assigned to shape modes" [43]. 

Transducers. Most modern electron spectrometers are based on solid-state, channel electron multipliers, which consist of tubes of glass that have been doped with lead or vanadium. When a potential difference of several kilovolts is applied across these materials, a cascade or pulse of 10 to 10 electrons is produced for each incident electron. The pulses are then counted electronically (see Section 4C). Several manufacturers are now offering two-dimensional multichannel electron detectors that are analogous in construction and application to the multichannel photon detectors described in Section 7E-3. Here, all of the resolution elements of an electron spectrum are monitored simultaneously and the data stored in a computer for subsequent display. The advantages of such a system are similar to those realized with multichannel photon detectors. 

The process of doping is accompanied by the appearance of gap levels in the electronic spectrum at low energies (near IR) at various Amax with a simultaneous blue shift and bleaching of the HOMO-LUMO (tt-tt ) strong electronic transition [61,62]. 

The existence of bipolarons (BP or dications) was easily established from the electronic spectrum even when their concentration in the samples prepared as films could not be known. The usual DIIR spectral pattern was observed for the films of the doped polymers, and its changes with time and temperature were taken to follow the dedoping process. The measurements could be made quantitative by ratioing the observed DIIR spectra to the weak signals arising from the C—H stretching modes of the alkyl substituents. These modes... 

It is evident that the use of doping-induced infrared spectra in the study of the stability of doped samples is an easy and useful alternative to the use of the electronic spectrum. 

Doping with alkali metals is an example of n-type doping (reduction of the polymer chain). Our calculations therefore include negatively charged defects (solitons) only. The impurity potential is in this case attractive (see Eq. (4)). Even though there is no exact electron-hole symmetry in the electronic spectrum in the presence of the extended Hubbard term (see Eq. (6) below), the properties of a p-type doped system are very close to those of a n-type doped system. Therefore, all results presented in the next section also hold for the case of p-type doping. 

The pristine material has a band gap of 2.0-2,5 eV as seen from UV-Vis spectropscopy and is a good insulator [113]. Upon chemical or electrochemical doping PTh can reach an electrical conductivity of a 50-100 S/cm [113]. Two interband transitions are observed in the electronic spectrum upon doping [114] the charge carrier carries a spin for dopant concentration below 3% [115]. Upon doping new... 

The electronic spectrum of PPV has been studied in detail by Obrzut et al. [170]. The infrared spectra of stretch oriented PPV have been recorded and widely studied by Bradley et al. [171] who have also studied the infrared spectra of doped [172] and pohotoexcited materials [173]. 

Llusar R, Casarrubios M, Barandiardn Z, Seijo L. Ab initio model potential calculations on the electronic spectrum of Ni +-doped MgO including correlation, spin-orbit and embedding effects. J Chem Phys. 1996 105 5321. 

Figure 1.19 presents the UV-Vis spectra of single and binary-doped PANl and also PAG. In single-doped PANI spectrum, three peaks at A.J = 380 nm, A.2=425 nm and 3= 800 nm, are observed. These three peaks are characteristic of doped PANl (emeraldine salt) [56] where is due to the electronic transition n to 71 band, is the electronic transition of the polaronic band to 71 band in the benzenoid ring and X corresponds to the electronic transitions of the n band to the polaronic band. The first two... 

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