Shpol skii effect

Shpol skii effect spect The occurrence of very narrow fluorescent lines in the spectra of certain compounds from molecules frozen at low temperatures. shpol-ske i,fekt ... 

Garrigues P, Ewald M. 1987. High resolution emission spectroscopy (Shpol skii effect) A new analytical technique for the analysis of polycyclic aromatic hydrocarbons (PAH) in environmental samples. Chemosphere 16 485-494. 

Shpol skii effect showing a number of optically resolvable origins (different trap sites) with 12 cm i halfwidths for the 0—0 bands. ODMR and optical electron-electron double resonance experiments showed that some of the optical origins themselves originate from multiple sites. 

Recently, alternate approaches to PAH-analysis have been proposed, which could possibly eliminate tedious separations in the future. These luminescence - based techniques make use of the Shpol skii effect, matrix isolation or fluorescence line narrowing spectrometry, combined with site selective laser excitationi Also, the refined mass spectrometric identification technique MS/MS was applied successfully to the analysis of PAH in synthetic fuels. 

Ambient temperature luminescence spectrometry has been applied to the characterisation of complex PAH-mixtures with only limited success because of excessive overlap of excitation or emission spectra. However, considerable sharpening of PAH absorption bands is observed, when these molecules are incorporated into appropriate matrices and solidified at low temperatures. Generally, three different techniques to achieve fluorescence line narrowing have been attempted, which only differ by the nature and the preparation of the host matrix. Methods to perform fluorescence line narrowing spectrometry (FLNS) are based on the Shpol skii effect, matrix isolation or the use of organic glasses. 

The exceptionally sharp, quasilinear spectra provided by PAHs under cryogenic sampling have aroused special interest in low-temperature fluorescence measurements on this type of pollutant. It has become apparent that low-temperature fluorimetry can be used to fingerprint specific compounds present at very low levels in PAH mixtures in various environmental matrices (e.g., sediments and biota) without the need for extensive prior cleanup. Low-temperature fluorimetric methods used for the analysis of PAH mixtures rely largely on the Shpol skii effect (in the frozen-solution or matrix-isolation mode). 

The selectivity of the Shpol skii effect lies in the inherently sharp absorption bandwidths of PAHs (FWHM 1-10 cm ) in appropriate frozen n-alkane hosts. Techniques based on this effect are usually very sensitive provided an optimal photomultiplier tube is used, the detection limit for pyrene in a mixture of 10 PAHs in -octane can be made as low as 5 X 10 °moll using an ordinary excitation lamp. The detection limit for benzo[a]pyrene is even lower by one order of magnitude two orders... 

In symmetrical porphyrins NH-tautomers do not distinguish in structure and have identical electronic spectra. Correspondingly, in most cases the spectral separation between the individual tautomers (a E) does not exceed 100 cm l and is due to crystalline matrix effect (6,7). Therefore, NH-tautomerism can be effectively detected at 77 K and 4.2 K in the Shpol skii matrix only at selective monochromatic excitation (5-7). In chlorins, the... 

Identification of amino- and nitro-substituted PAH may be effected by Shpol skii spectroscopy, a technique involving high resolution photoluminescence spectroscopy of the... 

A comprehensive review of hole burning spectroscopy of species in glasses has been prepared by Haarer and Silbey. Electric field effects on the spectral holes for perylene in Shpol skii matrices in n-heptane provide a useful extension of this technique . The limitations of the thermal lens method for the measurement of fluorescence yields have been examined and discussed . It is pointed out that the... 

A number of reports on phthalocyanines and porphyrins have been published. Spectral diffusion and thermal recovery of spectral holes burnt into phthalocyanine doped Shpol skii systems has been examined . An absorption, emission, and thermal lensing research on carboxylated zinc phthalocyanine shows the influence of dimerization on these properties. Fourier transformation of fluorescence and phosphorescence spectra of porphine in rare gas matrices has yielded much structural and electronic state data on this compound . Exciton splitting is an effect which is seen in the spectra of covalently linked porphyrins . A ps fluorescence study of the semirigid zinc porphyrin-viologen dyad has provided evidence for two dyad conformers . Spectral diffusion in organic glasses has been measured by observing the hole recovery kinetics over the time scale of 1 to 500 ms for zinc tetrabenzoporphyrin in PMMA . 

Typically, broad optical and microwave spectra are observed in low-temperature glasses except those of the Shpol skii type and very little magnetic information can be obtained. This is presumably because there are large contributions to the linewidth arising from the inhomogeneous broadening effects of random strains and sites. 

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