Influence of a metal surface on the luminescence of adsorbed europium compounds

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 6, pp. 130–134, November–December, 1995.     

Resonance raman spectra of π-anions of Zn-porphyrins

Institute of Molecular and Atomic Physics Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 2, pp. 128–136, March–April, 1995.     

The characteristic X-ray spectra of free atoms of metals

The article presents the results of a study of characteristic X-ray spectra of free atoms by means of a new simple technique. A pulsed electron beam was used for evaporation and to create inner-shell vacancies in free atoms of metals. The spectra were obtained with the help of an X-ray monochromator which allowed precise comparison between the free-atoms spectra and corresponding solid-state spectra. The shifts of the peaks were measured and found to be in the range Δλ/λ≈10⁻⁵–10⁻⁴. The K-, L- and M-series spectra were studied. A number of the free-atoms spectra revealed structure which was not resolved in the solid-state spectra and which is of interest for atomic structure calculation applications. This electron beam technique for the investigation of X-ray characteristic spectra of free atoms can be used for the refinement of X-ray wavelength standards.     

Isotopic effect in the vibronic spectra of europium compounds

The effect of the kinematic factor on vibronic spectra of europium compounds and Eu³⁺-doped lanthanide compounds was examined experimentally. It was demonstrated that isotopic or quasi-isotopic substitution of the ions of the crystal lattice gives rise not only to the changes of the vibration frequencies but also to alteration of the value of electron-phonon interaction. The latter displays in changing the relative integral intensity of vibronic sidebands of electronic transitions of Eu³⁺ ion. Eu³⁺ vibronic spectra of a number of pairs of natural and isotopically or quasi-isotopically substituted compounds: nitrates, halides, formates, acetates, oxalates, β-diketonates, etc., were studied. In most cases the substitution of deuterium for hydrogen was applied. Decrease of the electron-phonon interaction with the increase of the isotopic mass depends on different structural characteristics. It was found that a factor of decreasing the relative intensity of the vibronic sideband of electronic transition of Eu³⁺ ion lies within the range ∼1.2 and ∼7 for pairs of compounds under investigation. The largest change of the intensity of vibronic sidebands was observed in a pair of formates Eu(HCOO)₃ and Eu(DCOO)₃ having the tridentate-bridging coordination of the formate anions and a three-dimensional frame structure. One should take into consideration both decreasing the vibration frequencies and diminishing the value of electron-phonon interaction at introduction of heavy isotope or quasi-isotope in the crystal lattice of lanthanide compounds to reduce the multiphonon quenching of luminescence.     

A method for resolving individual bands in absorption spectra

A new algorithm for resolving individual bands in absorption spectra is developed. It is assumed that the spectrum consists of absorption bands with halfwidths determined by different kinds of interactions—specific and nonspecific. The method has good accuracy in the case of the strong overlap of bands (the ratio of the distance between maxima of the peaks to the halfwidth is less than 0.2) and a high computational efficiency. Arkhangelsk State Technical University, 17, Naberezhnaya Severnoi Dviny, Arkhangelsk, 163007, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 400–404, May–June, 1997.     

Vibrational spectra and stereoisomerism of the hexopyranose cycle in epoxysaccharides

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