L. Macalik

Polarized Raman spectra of the oriented NaY(WO4)2 and KY(WO4)2 single crystals

Abstract Polarized Raman scattering spectra of the NaY(WO 4 ) 2 (NYW) single crystal have been measured. Its structure is described in the tetragonal space group isomorphic to CaWO 4 scheelite. The A g , B g and E g spectra were made and discussed in terms of factor group analysis. These spectra are compared to those of monoclinic KY(WO 4 ) 2 (KYW) single crystals whose structure differs from the other crystal. The NYW unit cell comprises of the isolated WO 4 tetrahedra whereas the KYW structure is built from the WO 6 octahedra joined by WO 2 W double bonds and WOW single bridges. The vibrational characteristics of the bridge bond systems are proposed. On this basis, the role of the vibronic transitions for the KYW crystal doped with Eu 3+ ions is discussed.

Polarized infra-red and Raman spectra of monoclinic α-KLn(WO4)2 single crystals (Ln = Sm—Lu, Y)

Abstract The polarized i.r. and Raman spectra for single crystals of α-KLn(WO 4 ) 2 family were measured, where Ln = Y and lanthanides from Sm to Lu. The molecular and crystal structures were analysed in terms of C 2/ c = C 6 2 h (Z = 4) monoclinic unit cell. A comparison of vibrational spectra measured for isomorphic crystals of several RE elements was used to describe the internal and external optic modes. On that basis the hexacoordination of tungsten atoms and polymeric (W 2 O 10 ) n clusters with and bridge systems were discussed.

Effect of random distribution and molecular interactions on optical properties of Er3+ dopant in KY(WO4)2 and Ho3+ in KYb(WO4)2

Abstract The spectroscopic properties of Er3+ doped KY(WO4)2 and Ho3+ doped KYb(WO4)2 single crystals are reported and related to their X-ray structures. The experimental data include a survey of electronic absorption and emission features as well as vibrational IR and Raman spectra made in the polarized light. The effect of the random distribution of the monovalent and trivalent cations as well as intermolecular interactions between the tungstate anions are discussed.

Comparison of the spectroscopic and crystallographic data of Tm3+ in the different hosts: KLn(MO4)2 where LnY,La,Lu and MMo,W

Abstract Raman scattering and polarised infrared spectra of the potassium rare-earth double molybdates and tungstate (KLn x Tm 1− x (MO 4 ) 2 , where LnLa,Y,Lu, MMo,W) were measured at ambient temperature in the range of 40–1000 cm −1 . The assignment of the observed bands to the respective internal and external vibrational modes is proposed. The X-ray structural analysis of the yttrium thulium molybdate and lanthanum thulium tungstate crystals is reported. The crystal structure of the compounds studied depends on the type of cation and changes from monoclinic (for the lanthanum-thulium molybdate) to orthorhombic (for the yttrium- and lutetium-thulium molybdates). The character of the coordination sphere around the molybdenum atom changes from octahedral to tetrahedral.

Optical properties of Pr3+ in lanthanum double molybdates and tungstates: KLa1−xPrx(MO4)2 (M=Mo, W; x≤1)

Abstract Absorption, emission and excitation spectra of diluted single crystals of KLa1−xPrx(MO4)2 (M=Mo, W; x≤1) were measured. The intensities of the electronic transitions were analysed and related to the data of pure compounds. The fine structure of the electronic levels appearing in the optical spectra of the crystals is discussed. The temperature and concentration effects on intensities and the shapes of the observed bands are considered. Distinct vibronic sidebands were observed in the absorption, emission and excitation spectra for both systems. An assignment of the vibronic transitions is proposed and the single ion relaxation processes and the cooperative interaction are discussed.

Vibrational characteristics of the double oxygen bridge in the NaIn(WO4)2 and NaSc(WO4)2 tungstates with wolframite structure

Abstract The normal coordinate analysis of the tungsten–oxygen core in NaIn(WO 4 ) 2 and NaSc(WO 4 ) 2 crystals was performed. The Urey–Bradley force field and potential energy distribution (PED) were applied in the internal and external phonon calculations for the W 4 O 22 Na 2 In 2 molecular system. The dynamics of the asymmetric WO 2 W oxygen bridge as well as terminal WO bonds were analyzed and discussed. The vibrational characteristics of the oxygen double bridge bond, i.e. vibration energy, symmetry, force constants, PED, atomic displacements, direction of the transition dipole moments and mean square amplitudes were obtained and discussed. The theoretical considerations were based on the polarized IR and Raman spectra of the materials studied.

Ternary orthophosphates of the Ba3Y1−xNdx(PO4)3 family as possible powder laser materials

Abstract Ternary orthophosphates Ba 3 Y(PO 4 ) 3 doped with 0.05, 0.1, 0.15 and 0.2 Nd 3+ weight content were synthesized. The powder samples were separated according to their grain size and compared using spectroscopic data. Their IR, Raman, electron absorption and luminescence spectra were measured at room and liquid nitrogen temperature. The excited states of the Nd 3+ ions were characterized by means of decay curves of the life times. The possibility of the application of these materials as powder laser is discussed.

Comparative optical studies of lanthanide complexes with three types of phosphoro-azo derivatives of β-diketones

Abstract A new class of lanthanide compounds of the formula Na[LnL4]·H2O and LnC3·2H2O (where L=Wo or Az; Wo=CCl3C(O)NP(O)(OCH3)2; Az=C6H5C(O)NP(O)[N(CH2)2]2; C=CCl3C(O)NP(O)(NHC6H5)2) was obtained from mixed solvent solutions with the three types of phosphoro-azo derivatives of the β-diketones. Spectroscopic properties of these complexes are investigated and related to the structure and single crystal spectra of one of the above mentioned compounds [Amirkhanow et al., J. Appl. Spectr. 62 (1995) 5; Amirkhanow et al., Acta Phys. Polonica 90 (1996) 455]. The strong interaction of the ligands with the lanthanides was confirmed both by IR and electronic spectra. The intensities and splitting pattern of the electronic levels were used for the structure determination. IR and Raman spectra in the FIR and MIR regions have been recorded for solid lanthanide(III) (Eu, Pr, Nd) complexes with phosphoro-azo-β-diketones (Wo, Az and C). The normal coordinate analysis and potential energy distribution were performed for Ln(NPC2O4) molecular system consisting four chelate rings. On that basis, the assignment of the bands observed is proposed and related to the crystal structure of the complexes studied.

Promotional effect of molybdenum, chromium and cobalt on a VMgO catalyst in oxidative dehydrogenation of ethylbenzene to styrene

Abstract The influence of molybdenum, chromium and cobalt on the oxidation state and redox processes in VMgO catalyst is studied by means of X-ray diffraction and electron spin resonance spectroscopy. The results obtained are correlated with catalytic activity and selectivity. It is shown that molybdenum doping increases the selectivity and the chromium and cobalt doping improves the activity of the catalyst studied. The promotional effect of the dopants on the catalytic mechanism is discussed.

Vibrational properties of KLn(MoO4)2 crystals for light rare earth ions from lanthanum to terbium

Abstract Laser Raman and Fourier transform-IR spectra of potassium—rare earth double molybdates for lanthanides from La to Tb were recorded. Factor group analysis (FGA) was carried out and a vibrational assignment is proposed for the internal and external optic modes. The effect of 92Mo/100Mo isotope exchange on the IR and Raman transitions is discussed.