[en] The peculiarities of nonradiative and irradiative relaxations with radiation defects creation in alkaline halogen crystals (AHC) (NaCl, KCl, CsBr, K Br, KI, RbI, CsI and Na Br) at lattice symmetry lowering bu uniaxial elastic deformation were investigated with experimental methods of luminescence spectroscopy. Energy of activation of STE luminescence suppression in AHC is experimentally estimated at low temperature uniaxial deformation: the increase in value of activation energy is observed in the range KBr(Cs)→NaCl→KI→ Na Br→CsBr→RbI; it is established, that in Sc I crystals (ε219-223 meV) and KBr (ε=26-33 meV) activation energy of STE nonradiative decay practically does not change, and for other crystal values of ε sharply increases. The effect of STE intrinsic luminescence strengthening in AH is interpreted on the basis of the potential barrier's growth, that share s radiative and nonradiative channels of STE decay. (author)

[en] The formation of iodate complexes of calcium, strontium, barium at 25 deg and ionic strengths μ=0.5; 1.0; 2.0; 3.0; 4.0; 6.0; 8.0 was studied by the method of solubility. Stability constants of the complexes at the zero ionic strength were calculated according to the values of stoichiometric constants. The stability constants depending on the ionic streno.th of the solution for all the investigated systems decrease initially, pass through a minimum and then grow which is related to changes in the activity constants of the reacting ions. However, the minimum of the Ba(IOsub(3))=sup(2-n) stability constants is considerably displaced to the side of higher values of μ(2-3) ac compared to its position for Ca(IO)sub(3)sub(n)sup(2-n) and Sr(IOsub(3))=sub(n)sup(2-n) (μ approximately 1.0)

[en] With a liquid desorption FAB source it is possible to obtain alkaline earth metal ions complexed by a crown ether. Conditions for formation of these complexes ions are examined for selection of the complexing agent in function of cation size. Behaviour of alkaline and alkaline earth compounds are compared allowing the differentiation of ion extraction phenomena by liquid desorption ion source and solvent extraction

[en] We have studied the complexes of alkaline-earth elements in anhydrous acetic acid. Using glass-electrode potentiometry we have studied the titration of alkaline earth acetates with perchloric acid which is the strongest acid in anhydrous acetic acid. These titrations have shown that the basic strength of these acetates increases as follows: Mg < Ca < Si < Ba. The interpretation of the titration curves has made it possible to determine a certain number of reaction constants. A study has also been made of the dissociation, of alkaline earth perchlorates formed during these titrations, since the determination of the reaction constants involves their dissociation constants. During this work it has been possible to show that barium has a particular behaviour, giving a mixed compound (a lower acetate complex) not only in the presence of perchloric acid but also in the presence of sulfuric and hydrochloric acids. These are respectively: the mixed acetate-perchlorate complex of barium: Ba(OAc) (ClO₄); the mixed acetate-acid sulfate complex of barium: Ba (OAc)(HSO₄); the mixed acetate-chloride of barium: Ba (OAc)(Cl). (author)

[en] Full text: Several new quaternary compounds from the rare-earth metal group-13 chalcohalide family have been prepared from alkaline earth halide flux reactions of binary and elemental starting materials. One compound, for example, Ca₂La_6Ga₂S₁4 , crystallizes as needles in an hexagonal cell while another, more disordered structure, La₁₁Ga₁₉Cl₆S₄₂ , crystallizes as monoclinic plates. The former is a condensed structure with channels that contain the alkaline earth element while the latter forms a layered structure containing rare-earth halide clusters within interlayer galleries. These compounds are new members of a family of rare-earth metal main-group chalcogenides which show promise as electroluminescent materials. Structural and spectroscopic studies of these and related compounds will be discussed

[en] Multiple-collision relaxed (helium) chemiluminescence and laser-induced fluorescent spectroscopy have been used to demonstrate the highly efficient collisional stabilization of electronically excited Group IIA dihalide collision complexes formed in M (Ca,Sr)+X₂ (XY) (Cl₂, Br₂, ICl, IBr, I₂) reactive encounters. The first discrete emission spectra for the CaCl₂, CaBr₂, SrCl₂, SrBr₂, and SrICl dihalides are observed and evaluated; however, the low-pressure 'continuous' chemiluminescent emission observed for forming barium dihalide (BaX₂) complexes is quenched under these experimental conditions. The reactions of the Group IIA metals with molecular fluorine do not readily produce the corresponding dihalide. While the lowest-lying observed dihalide visible transition is, as predicted, found to result in an extended progression in a dihalide complex bending mode (SrCl₂), the observed progression suggests the presence of a residual halogen (Cl-Cl) bond. Two higher-lying transitions are dominated by a vibrational mode structure corresponding to progressions in the symmetric stretching mode or, for nominally forbidden electronic transitions, odd quanta of the asymmetric stretching mode. Some evidence for sequence structure associated with the dihalide bending mode is also obtained. These observations are consistent with complex formation as it is coupled with a modified valence electron structure (correlation diagram) associated with the highly ionic nature of the dihalides. The bonding in the Group IIA dihalides (and their complexes), whose atomization energies are more than twice the metal monohalide bond energy, strongly influences the evaluation of energetics and the determination of monohalide bond energies from chemiluminescent processes. Discrepancies between those bond strengths determined by mass spectrometry and chemiluminescence are discussed with a focus on energy partitioning in dihalide complex formation and its influence on chemical vapor deposition. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

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