Low temperature luminescence

Luminescence instrument LS-3B luminescence instrument LS-5B Accessories low flow cell, cell holders, bioluminescence spectroscopy, fluorescence spectro scopy, recorder/printers, low-temperature luminescence, fluorescence plate reader, polarization accessory, microfilm fluorimeter LS-2B... 

Photoconductivity (17,170) and transient absorption spectroscopy (36) studies indicate that (S+Au)-sensitization causes electron trap formation or deepens existing traps, but does not provide evidence that the traps are deeper than those produced by S-sensitization alone. Low-temperature luminescence studies likewise indicate that the gold does not enhance the electron trapping (172). 

The low temperature luminescence spectra of the title compounds in poly(methyl methacrylate) (PMMA) are shown in Fig. 4. In addition to the solvatochromic effect the MLCT luminescence bands show a pronounced rigidochromic effect. However, not only the emission energies, but also the band shapes change when the low viscosity solvents are replaced by a rigid glassy matrix. 

Examples of the low temperature luminescence spectra are shown in Fig. 8.12. The luminescence intensity is highest in samples with the lowest defect density and so we concentrate on this material. The role of the defects is discussed in Section 8.4. The luminescence spectrum is featureless and broad, with a peak at 1.3-1.4 eV and a half width of 0.25-0.3 eV. It is generally accepted that the transition is between conduction and valence band tail states, with three main reasons for the assignment. First, the energy is in the correct range for the band tails, as the spectrum lies at the foot of the Urbach tail (Fig. 8.12(6)). Second, the luminescence intensity is highest when the defect density is lowest, so that the luminescence cannot be a transition to a defect. Third, the long recombination decay time indicates that the carriers are in localized rather than extended states (see Section 8.3.3). 

Evidence for the Auger process is contained in the low temperature luminescence data in Fig. 8.19 (Street 1981b). The thermal quenching... 

Core vibrational frequencies obtained by Raman or resonance Raman spectrophotometric technique are summarized in Table V (53, 113, 116-118). The p(Pt—Pt) bands for the pop complexes [Pt2(pop)4] " (PtdDa), [Pt2(pop)4X] - (Ptdl,111)2), and [Pt2(pop)4X2] - (Pt(III)2) increase in the order expected from increasing Pt—Pt interaction (53). Resonance Raman spectra have been used frequently for the assignment of the electronic transitions of complexes as listed in the table. Also, observation of the vibrational structure in the low-temperature luminescence spectra coupled with the data in the table has been useful for considering the nature of the transition of these diplatinum complexes. The resonance Raman spectra at the intervalence band of the three mixed-valence complexes, which are stable only in the solid state, indicate that [Pt2(pop)4Cl] is a localized valence species and the bromo and iodo analogues are nearly delocalized valence species (53). 

A low-temperature luminescence system with a pulsed-source luminescence spectrometer has been designed. " A method for the analysis of luminescence data for mixtures adsorbed on filter paper is also of interest. " Similar methodology is well suited to the examination of air pollution. "... 

Liquid air Air that has been cooled to a very low temperature. Luminescence The property of giving off light without giving off heat. 

Low-temperature luminescence spectra of naphthalene (Nph) adsorbed in the alkali and alkaline-earth forms of the X zeolites indicate molecules physically adsorbed and bound in donor-acceptor complexes. Using spectral methods the Nph oxidation reaction has been found to be promoted by water vapor. The oxygen chemisorbed in the cages is considered as an oxidizer of Nph. Nph forms photostable dimer associates on the surface of amorphous aerosil. 

Low-temperature luminescence spectra of //vibronic structure involving v0=0s=0 (885 cm-1) and vsOs NC S (255 cm-1) modes.324 Detailed skeletal mode assignments, with normal coordinate analyses, were reported for [OsCl4X(SeCN)]2 and OsCUX-tNCSe)]2-, where X = Cl or I.325 326... 

Next to the luminescence of uranium-doped oxides the luminescence of uranium-activated alkali halide samples has also been known for a long time L The low temperature luminescence spectra of uranium-doped sodiumfluoride (NaF—U) are rather complicated. The spectra depend on the uranium concentration as well as on the growth conditions. Samples grown in an oxiding ambient yield the most efficient luminescence. The bright luminescence of NaF—U has been used for the quantitave analysis of uranium ). 

As the starting point for the discussion of energy transfer processes, the luminescence properties of the unperturbed chromophores have to be determined. This has to be done by doping them at low concentration into an isostructual host-lattice using cations which are photophysically inert in the spectral region of interest, as for instance [Rh(bpy)3][NaAl(ox)3]C104. Accordingly, Fig. 6 shows the low-temperature luminescence spectra of the two chromophores doped into the above host lattice. The two emission spectra... 

Keywords Nitroxide radicals Lanthanide complexes Low-temperature absorption spectroscopy Low-temperature luminescence spectroscopy Molecular magnetism... 

Fluorescence applied to oil identification has been an active field, with 17 papers presented on the subject at the last three Pittsburgh Conferences. A number of interesting developments for fluorescence and low-temperature luminescence (LTL) are described by Eastwood et al. (58). These include synchronous scanning, difference spectrofluorometry, synchronous difference spectroscopy, derivative spectroscopy, and total luminescence (or contour) spectroscopy and combinations of these techniques. In a recent presentation, Eastwood and Hendrick (59) reported an extension of their low-temperature luminescence studies to include polarized excitation and emission spectroscopy, and time-resolved phosphorescence. Preliminary studies of polarization effects indicate that differences exist in low-temperature polarized luminescence spectra of oils, which may aid in oil identification. In the time-resolved phosphorescence spectra of oils, the most significant difference observed was enhancement of the vanadyl porphyrin signal at approximately 700 nm for short delay times (20 fxsec). 

The capabilities of various analytical methods are reviewed, such as capillary gas chromatography, high pressure liquid chromatography, thin layer chromatography and low temperature luminescence spectrophotometry. A candidate list of high priority PAH/POM compounds, including some representative heterocyclic compounds, which is based on occurrence in environmental emissions, health effects and analytical considerations, is discussed. 

In addition, a number of advanced analytical techniques, such as low temperature luminescence spectroscopy, tandem mass spectrometry (MS/MS), Fourier-Transform IR-spectroscopy and nuclear magnetic resonance spectrometry have been successfully applied to PAH analysis. For instance, low temperature luminescence spectrometry, sometimes in combination with laser excitation, was used for the analysis of PAH in various matrices without prior separation, which is attractive especially for screening or finger-printing purposes (10, 73). However, a wider application for routine analysis is at present inhibited by the limited availability of the required equipment. The same remark applies to tandem mass spectrometry, FT-IR spectroscopy and NMR. All three techniques, however, are increasingly used for the detection and identification of novel PAH species and derivatives and efforts are continuing towards coupling IR and NMR as detectors to GC and HPLC (74) respectively. 

UV-, IR- and fluorescence spectra (including some low temperature luminescence spectra)... 

Xia T, Zhuang WD, Cui XZ, Zhao CL, Teng XM, Huang XW (2006) Low temperature luminescence properties of Tm doped aluminate phosphor. J Rare Earths 24 141... 

The room temperature fluorescence excitation and emission spectra were recorded for the 1000 ppm solutions of the compounds. The same solutions were then transferred to the thick-walled sample tubes aligned in the quartz Dewar flask containing liquid nitrogen. The low temperature luminescence excitation and emission spectra were then recorded. The phosphorescence spectra at -196 °C were then obtained after the phosphoroscope rotating can had been fitted. The phosphorescence life-time was determined by observation of the decay curve of the phosphorescence on the X-Y recorder or with the oscilloscope. 

Working curves for both low temperature luminescence intensity (phosphorescence plus fluorescence) and phosphorescence intensity versus concentration in parts per million of the compound in the solvent mixture were obtained for each of the stabiliser compounds which exhibited appreciable luminescence. The wavelengths of maximum excitation and... 

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