Thallium, excited, from

The aim of this work is the development of pyrene determination in gasoline and contaminated soils. For this purpose we used room temperature phosphorescence (RTP) in micellar solutions of sodium dodecylsulphate (SDS). For pyrene extraction from contaminated soils hexane was used. Then exttacts earned in glass and dried. After that remains was dissolved in SDS solution in the presence of sodium sulphite as deoxygenation agent and thallium (I) nitrate as heavy atom . For pyrene RTP excitation 337 nm wavelength was used. To check the accuracy of the procedures proposed for pyrene determining by RTP, the pyrene concentrations in the same gasoline samples were also measured by GC-MS. 

Of the above three s ions, most data have been obtained for Pb . The reason is that this ion gives the best Sq -> Pj absorption spectrum the bismuth(III) spectral band tends to be somewhat broad (see above) and the thallium (I) band often has a shoulder, or even consists of two distinct maxima, an effect which has been attributed possibly to the Jahn-TeUer effect in the excited state (75). From Eq. (2) and data in... 

The mechanism just discussed is a simplified one which has not been tested experimentally in great detail. The thallium radiation emitted from a system of Hg and T1 vapor on excitation was studied many years ago by Compton and Turner13. It might be interesting to pursue these studies further with modem techniques,... 

As commented above, different compositions lead to different emission energies, and these systems emit at 646, 609, 620, 606, and 683 nm, respectively, by excitation at 550 nm. Furthermore, there is no correspondence of the emissions with the gold-thallium lengths since all of them range from 2.9 to 3.1 A or with the environment around the thallium centers. As a plausible explanation it was reported that each 2D or 3D network could probably lead to different excited states, and the formation of such networks might be influenced by the presence or absence of coordinating solvents in their structures. 

Murillo-Pulgarin et al. used a phosphorimetry method for the determination of dipyridamole in pharmaceutical preparations [44]. Ten tablets or capsules were powdered and homogenized, and then 0.1 g was dissolved in 0.1 M sodium dodecyl sulfate. The determination of dipyridamole was carried out in 26 mM sodium dodecyl sulfate/ 15.6 mM thallium nitrate/20 mM sodium sulfite, whose pH was adjusted to 11.5 by the addition of sodium hydroxide. After 15 min at 20°C, the phosphorescence was measured at 616 nm (after excitation at 303 nm). The calibration graph was linear from 100-1600 ng/mL, with a detection limit of 16.4 ng/mL. Relative standard deviations were in the range of 0.5-7.3%, and sample recoveries were in the range of 95-97%. 

It is obvious from Table 4.6 that the problem of excitation transfer from mercury to thallium is in a very unsatisfactory state. There is an apparent lack of consistency in the results of Kraulinya et al. (104), whose cross sections for excitation transfer to the 8 2S1/2, 6 2D2/2, and 7 2S1/2 levels in thallium seem to depend on the wavelength of the observed fluorescent component. The results of the two groups (Hudson and Curnutte and Kraulinya et al.) do not agree well with each other, and there is no consistent dependence of the measured cross sections on temperature. Finally, one would expect that the cross sections should decrease in some manner with increasing energy gap AE, but the results seem to indicate the opposite. It is manifest that considerable additional experimental work is needed to overcome these difficulties. 

Cross Sections Q for Excitation Transfer from Hg63P to Various Levels in Thallium AE Denotes the Energy Difference between the Appropriate Thallium Level and Hg 6 3P Temperatures Are Given in °K... 

Studies of excitation transfer induced in collisions with molecules were not limited to fine-structure states of alkali atoms. Excitation transfer from the 621>3/2 to the 6 2 >5/2 state in thallium was investigated in a Hanle experiment... 

In addition to the exciton band, energy states may be created between valence and conduction bands because of crystal imperfections or impurities. Particularly important are the states created by the activator atoms such as thallium. The activator atom may exist in the ground state or in one of its excited states. Elevation to an excited state may be the result of a photon absorption, or of the capture of tm exciton, or of the successive capture of an electron and a hole. The transition of the impurity atom from the excited to the ground state, if allowed, results in the emission of a photon in times of the order of 10" s. If this photon has a wavelength in the visible part of the electromagnetic spectrum, it contributes to a scintillation. Thus, production of a scintillation is the result of the occurrence of these events ... 

In 1962, Sugano showed that the Seitz model (115) could be interpreted as a molecular orbital model (123), an interpretation that clarifies analysis of these systems. In this interpretation, the absorption bands observed in the TI(I) doped alkali halide system come from the electronic transition aigf a g) hu), but the excited states are still calculated assuming an ionic interaction between the metal and the hgand. Since the thallium-chlorine bond is actually largely covalent, Bramanti et al. (118) modified the approach and used a semiempirical molecular orbital (MO) calculation to describe the energy levels of T1(I) doped KCl. Molecular orbitals were constructed by the linear combination of atomic orbitals (LCAO) method from the 6s and 6p metal orbitals and the 3p chlorine orbitals. Initial calculations were conducted with the one-electron approximation the method was then expanded to include Coulomb and spin-orbit interactions. The results of Bramanti et al. were consistent with experimental... 

Upon substitution of 30% of the sodium counterions in the SDS micelle with thallium, a similar chromatogram is observe (Fig. 12.6B). These signals also arise from fluorescence and are diirimished in intensity compared to Fig. 12.6A, because thallium is effectively depopulating the excited singlet state from which fluorescence occurs. Thus, Fig. 12.6A... 

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