The excitation spectra of tetrahedral complex compounds of manganese(II) bromide with hydrobromides of some derivatives of pyridine and pyperidine

The excitation spectra of complex compounds of magnanese (II) bromide with hydrobromides of some derivatives of pyridine and pyperidine have been studied at temperatures of 77 and 298 K. The character and arrangement bands of the excitation spectra as well as the green luminescence observed are indicative of tetrahedral structure of these compounds. The mechanism of production of the spectra has been explained in terms of ligand field theory. The Racah parameters calculated and the value of 10Dq was estimated to be about 3100 cm^–1. In analyzing the excitation spectra an original method of computation was applied which gave very good results in resolving the bands.     

On the luminescence of manganese(II) phosphates

Luminescent properties of manganese(II) phosphates prepared by thermal dehydration of Mn(H₂PO₄)₂·2H₂O have been studied. The emission spectrum consists of two bands whose relative intensity and spectral position depend on the chemical and crystalline structure of phosphates. The different courses of temperature quenching of luminescence intensity and excitation spectra of each emission band of Mn(H₂PO₄)₂·2H₂O, Mn(H₂PO₄)₂, MnH₂P₂O₇ and c-Mn₂P₄O₁₂ are discussed.     

On the measurement of luminescence excitation spectra

A method is presented for the unique determination of excitation spectra for non-linear luminescence, assuming only that the non-linearity occurs subsequent to absorption.     

The luminescence of II–VI compounds with blende type structure under high excitation

The luminescence of ZnSe is investigated as a function of excitation intensity for temperatures between 5 K and 300 K. At low excitation we observe emission due to free and bound excitons and due to donor-acceptor pair recombination. At higher excitation, the emission is dominated by inelastic exciton-exciton and exciton-free carrier scattering at lower and higher temperatures, respectively. A “M-band” observed in ZnSe and ZnTe is tentatively ascribed to a biexciton decay. The biexciton binding energies are 2±1 meV for ZnSe and 1,5±1 meV for ZnTe.     

Quantitative analysis of dinuclear manganese(II) EPR spectra

A quantitative method for the analysis of EPR spectra from dinuclear Mn(II) complexes is presented. The complex [(Me(3)TACN)(2)Mn(II)(2)(mu-OAc)(3)]BPh(4) (1) (Me(3)TACN=N, N('),N(")-trimethyl-1,4,7-triazacyclononane; OAc=acetate(1-); BPh(4)=tetraphenylborate(1-)) was studied with EPR spectroscopy at X- and Q-band frequencies, for both perpendicular and parallel polarizations of the microwave field, and with variable temperature (2-50K). Complex 1 is an antiferromagnetically coupled dimer which shows signals from all excited spin manifolds, S=1 to 5. The spectra were simulated with diagonalization of the full spin Hamiltonian which includes the Zeeman and zero-field splittings of the individual manganese sites within the dimer, the exchange and dipolar coupling between the two manganese sites of the dimer, and the nuclear hyperfine coupling for each manganese ion. All possible transitions for all spin manifolds were simulated, with the intensities determined from the calculated probability of each transition. In addition, the non-uniform broadening of all resonances was quantitatively predicted using a lineshape model based on D- and r-strain. As the temperature is increased from 2K, an 11-line hyperfine pattern characteristic of dinuclear Mn(II) is first observed from the S=3 manifold. D- and r-strain are the dominate broadening effects that determine where the hyperfine pattern will be resolved. A single unique parameter set was found to simulate all spectra arising for all temperatures, microwave frequencies, and microwave modes. The simulations are quantitative, allowing for the first time the determination of species concentrations directly from EPR spectra. Thus, this work describes the first method for the quantitative characterization of EPR spectra of dinuclear manganese centers in model complexes and proteins. The exchange coupling parameter J for complex 1 was determined (J=-1.5+/-0.3 cm(-1); H(ex)=-2JS(1).S(2)) and found to be in agreement with a previous determination from magnetization. The phenomenon of exchange striction was found to be insignificant for 1.     

Structure and luminescence properties of antimony(III) complex compounds

The influence of the structure of the anion sublattice on the spectral luminescence properties is investigated using the example of antimony(III) complex compounds with outer-sphere organic cations. It is established that the factors favorable for the enhancement of the luminescence of antimony(III) ions are the island structure of the anion sublattice with minimum distortions of the antimony(III) coordination polyhedron and closely spaced energy levels of the outer-sphere organic cation and the antimony(III) ion.     

Structure and luminescence properties of tellurium(IV) complex compounds

Using the tellurium(IV) complex compounds as an example, we study the interrelation between the geometric structure and spectral luminescence properties. We find that, in the series of compounds of Te(IV), which are characterized by the island octahedral coordination of Te(IV) ions, the luminescence intensity depends on the degree of distortion of the Te(IV) coordination polyhedron, the Stokes shift, and the energy of the luminescence transition. We revealed that the considered series of Te(IV) compounds possess reversible thermochromic properties.     

Magnetic field effect on the luminescence of the paired Ag- ions in alkali halides (II)

The fine structure of the relaxed excited state of paired Ag^- ions in KBr and RbBr is studied by measuring the magnetic field effects on the decay time of the luminescence at about 2 K. The experimental results obtained are found to be well explained theoretically by assuming thermal equilibrium, with the exception of an anomalous change at about 43 kG(KBr) or at about 34 kG(RbBr). The anomalous change exhibits a level crossing and also shows that the Zeeman levels do not reach the thermal equilibrium at least in the neighborhood of the level crossing.     

He(I) and He(II) photoelectron spectra of some organo-mercury compounds with carbon π-systems

The UV photoelectron spectra of a series of aromatic mercury derivatives {(C₆H₅)₂ Hg, (pCH₃C₆H₄)₂Hg, C₆H₅HgCl, pCH₃C₆H₄HgCl} and of a series of alkynyl mercury derivatives {(CH₃C)₂Hg, ((CCH₃)₃CCC)₂Hg, (ClCC)₂Hg} are reported and discussed. Particular attention is devoted to possible interactions between mercury orbitals and π systems of the ligands. In this respect differences are observed between the two series: in the alkynyl derivatives ligand-field effects are evident on the 5d mercury orbitals, whilst they are not observable in the aromatic compounds.     

The fluorescence spectra of pharmaceutical compounds under two-photon excitation

Spectra of two-photon-excited fluorescence in pharmaceutical crystalline compounds were obtained and studied as functions of the pump power and delay time. Stimulated fluorescence was observed in polycrystalline Novocaine under high-power pumping. The spectra of two-photon-excited fluorescence in pharmaceutical compounds are localized within the wavelength range of 270–480 nm. The most intense fluorescence was observed in the Novocaine polycrystals. The therapeutic effect of diphenylhydramine and sulfanilamide is attributed to the fact that the energy of optical quanta of the fluorescence emission in these substances is higher than the energy of excited π-electrons in tryptophan and nucleotides. The data obtained for the spectra of the pharmaceutical substances studied can be used to solve analytical problems related to identification of the composition and properties of composite pharmaceutical substances.     

Size-induced effect on cathode luminescence spectra of CsI(Na) and CsI(Tl) crystals

We investigated the cathode luminescence characteristics of CsI(Na)and CsI(Tl)crystals by the spectrum and structure properties at room temperature.We fabricated three different sizes of CsI(Na)and CsI(Tl)crystals and measured their luminescence spectra under cathode rays.We found that CsI(Na)cathode luminescence peaks appear at 420 and 305 nm,and CsI(Tl)cathode luminescence peaks are 540 and 410 nm,the grain size affects CsI(Na)luminescence significantly,and the Na-related420 nm luminescence intensified relatively when the average grain size reaches~20μm,which becomes weak when the grain size is down to nano-scale.But the cathode luminescence spectra of CsI(Tl)crystals with different size have no obvious changes.Our explanations for these phenomena are that the different impurities in the same host material CsI lead to different luminescence mechanisms.These cathode luminescence characteristics indicate the suitability of CsI(Na)and CsI(Tl)crystals to match photomultiplier tube for large area crystal detector development.