Antiferromagnetism in Rb2MnCl4·2H2O

Specific heat measurements in the temperature range 1.38° – 4.03°K indicated a λ-type anomaly at 2.24°K which has been identified as a paramagnetic-antiferromagnetic transition. Short range ordering accounts for approximately 25% of the total entropy change. The calculated sublattice magnetization is compared to several statistical models.     

Quasi-reversible superprotonic phase transition in K9H7(SO4)8 · H2O crystals

The heat capacity and the bulk conductivity have been measured in the K₉H₇(SO₄)₈ · H₂O crystal. The hysteresis phenomena have been studied upon superprotonic phase transition. It is revealed that the phase transition is reversible upon thermocycling only for the monohydrate form of the crystal. The exponential temperature dependence of the heat capacity in the supercooled disordered phase exhibits a thermally activated behavior and is determined by the defects responsible for the high conductivity of the crystal.     

Zero-field NMRON in54Mn-MnCl2·4H2O

We have observed NMRON lines for⁵⁴Mn doped into MnCl₂.4H₂O corresponding to ordering by a strong hyperfine field B_N=60.95 (6) T modified by a weak quadrupole interaction of strength P=+0.52 (7) MHz. The reduction of S_Z for the manganese ion is larger than expected. Point-charge estimates of P yield values which are positive, but smaller than the experimental value.     

Electronic spectra of chromate doped 3CdSO4 · 8H2O crystals

The optical absorption spectra of CrO^2-₄ doped 3CdSO₄ · 8H₂O crystals revealed four bands. The two prominent bands at 27, 030 and 36, 360cm^-1 along with the featureless, intense band at 41, 670cm^-1 are assigned to the electronic transition ¹A₁→¹T₂. The lowest energy band at 24,100 cm^-1 is attributed to the orbitally forbidden transition ¹A₁→¹T₁ in accordance with the Molecular Orbital scheme of Viste ang Gray. The spectrum recorded at 80 K exhibited a fine structure superposed on the two prominent bands. The structure is ascribed to the vibrational progression of totally symmetric breathing mode in CrO^2-₄ ion.     

Magnetic transitions in K2MnCl4·2H2O

Results of (dM/dH) measurements on tetrahedral K₂MnCl₄·2H₂O as a function of temperature and magnetic field, are presented. An antiferromagnetic transition along the tetragonal axis is observed at T_N = (3.05±0.05) K. The H-T magnetic phase diagram was completely determined, and shows the usual characteristics of that of a low anisotropy antiferromagnet. The T = 0 critical fields are compatible with the values H_E = (29.2±0.3) kOe and H_A = (5.9±0.6) kOe for the exchange and anisotropy fields.     

EPR studies of Cu2+ ion in CdK2 (SO4)2·6H2O single crystals

The EPR spectra of Cu²⁺ in CdK₂(SO₄)₂·6H₂O crystals have been studied at 77 K and 300 K in three (bc, a¹c and a¹b) planes. The angular variation spectra showed that the Cu²⁺ ion enters the Cd²⁺ site in the lattice. The principal g and A values, covalency parameter (α'²), mixing coefficients (α and β) and Fermi-contact term (K) have been evaluated from the EPR analysis. The ground-state wave function of the Cu²⁺ ion has been constructed using the α'², α and β values, and the signs for the hyperfine coupling constants are also determined. The covalency value indicates the percentage of unpaired spin density present at the metal (Cu²⁺) d orbital. The nature of the distortion present in the lattice is obtained from the values of the mixing coefficients.     

Picosecond third-harmonic light generation inβ-BaB2O4

The type-II phase-matched third-harmonic light generation in a -BaB₂O₄ crystal is studied experimentally. A passively mode-locked Nd: phosphate glass laser is used as a pump source. At a pump pulse peak intensity ofI ₁₀=5×10¹⁰W/cm² a third-harmonic conversion efficiency of a percent is obtained. A theoretical discussion of phase-matched third-harmonic generation in crystals of the symmetry group of -BaB₂O₄ (trigonal class 3) is given. The effective nonlinear susceptibility _eff for type-II phase-matching is determined.On leave from the Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, Shanghai, P.R. China     

Electron spin resonance of O−3 trapped in Ba(C1O3)2 ·H2O single crystals

O⁻₃ has been trapped as an isolated paramagnetic center after u.v. photolysis of an X-irradiated single crystal of Ba(C1O₃)₂ ·H₂O. The ESR spectrum has shown that there are two magnetically inequivalent sites and the principal g values are obtained as 2.0146, 2.0098 and 2.0017 with an average value of 2.0087. The optical absorption band at 435 mμ is strongly polarized along the [001] direction.     

Proton nuclear magnetic resonance in paramagnetic NiSO4 · 1 H2O

Parameters characterizing the magnetic interactions between the paramagnetic ions Ni²⁺ and the protons of crystalline water in powderedNiSO ₄ · 1H ₂O were derived from the field and temperature dependences of the second moment of NMR spectra. The Curie-Weiss constant, magnetic moment _i and the part of second momentM ₂O corresponding to the nuclear dipoledipole interaction were evaluated from the experimental data. The parameters characterizing the local magnetic field acting on the proton-pairs were calculated and compared with those obtained from the analysis of the shape of the NMR spectrum.The authors express their grateful acknowledgement to Prof. Dr. hab. Z. Pajak, Dr. S. GIo-winkowski, Dr. J. Kapturczak and Ing. W. Porzuckoviak from Institute of Physics, A. Mickiewicz University in Poland for their help in NMR measurements and fruitful discussions.     

Resonanzaufspaltung im Schwingungsspektrum des CaSO4·2H2O

The resonance- or Davydov- or correlationfield-splittings of the vibrational levels of CaSO₄·2H₂O (gypsum) are calculated using the exciton theory ofDavydov. This theory is extended to include the induced polarization of crystalline matter by the electric fields of the transition dipoles. The numerical calculations are based on an experimental determination of the transition dipole moments and on a calculation of the dipole lattice sums by the Ewald method. The results obtained show, that in most cases the assumption of Coulomb interaction between transition dipoles alone does not completely explain the observed splittings. However, the shift of transition frequency with an increasing longitudinally polarized component of a polar crystal vibration can be predicted by this theory within the limits of accuracy of the experimental determination of transition moments.     

Das Schwingungsspektrum des monoklinen CaSO4·2H2O

The relations between the imaginary part of the optical dielectric tensor in molecular crystals and transitions active in absorption, derived in a preceding paper [1], are experimentally verified by investigating the vibrational spectrum of monoclinic crystals of gypsum. Reflection spectra of precisely oriented crystal sections were recorded using polarized light between 10 000 cm^?1 and 300 cm^?1 at room temperature and at about 15°K. The eigenfrequencies of polar vibrations and the direction and magnitude of transition moments in the crystal are derived from these spectra. These results definitely support the assumption, that the bands observed between 500 cm^?1 and 300 cm^?1 are caused by hindered rotations of the water molecules. The temperature dependence of the spectra of these molecules in the region of the two stretching modes indicates mixing of these states as a result of the crystalline field. Besides this, mechanisms are discussed, which lead to the decay of excited vibrational modes and thus give rise to the observed temperature dependence of the bandwidths.     

The proton magnetic resonance study of the structure of Na2Zn(SO4)2·4H2O

The proton magnetic resonance spectra of single crystals of Na₂Zn(SO₄)₂·4H₂O have been investigated and the orientations of the water molecules have been determined. Using the heavy atom structure determined by X-rays a system of hydrogen bonds between water and sulphate oxygens has been proposed.     

E.P.R. study of γ-irradiated single crystals of K2C2O4.H2O and (NH4)2C2O4.H2O

The electron paramagnetic resonance of γ-irradiated single crystals of K₂C₂O₄.H₂O and (NH₄)₂C₂O₄.H₂O has been studied. The spectra show interesting microwave power saturation effects. The singlet spectrum is attributed to the C₂O₄ ^- radical derived from the C₂O₄ ^-- ion. The principal g-values are determined to be 1·998, 2·0028 and 2·0004. Certain weak lines are observed with different power saturation and interpreted as due to OH radicals derived from water molecules in the crystal lattice.     

The crystal structure of tetrammine copper sulphate Cu(NH3)4SO4·H2O

The crystal structure of tetrammine copper sulphate was determined. The orthorhombic unit cell with dimensions a=12.12, b=10.66, c==7.07 Åcontains four molecules of Cu(NH ₃)₄ SO ₄.H ₂ O, the space group is Pbnm (D _2h ¹⁶ ).The atomic coordinates were determined from the projections of the Patterson function and the electron density onto the (001) and (010) planes. The complex cation Cu(NH ₃)₄ ⁺⁺ is approximately planar, the groups of NH ₃ are linked by co-valent bonds to the central Cu atom. The average distance of the groups of NH ₃,which are approximately at the corners of a square surrounding the central Cu atom, is 2.90 Å, the distance Cu-NH ₃,corresponding to the co-valent bond, is 2.05 Å.     

超分子化合物C11H6N2O·H3PO4·H2O的合成与晶体结构

采用水热反应法合成超分子化合物C11H6N2O·H3PO4·H2O,通过元素分析、红外光谱和X射线单晶衍射对其组成、结构进行分析.该化合物属于三斜晶系,空间群P-1,晶胞参数a=0.73350(6)nm,b=0.74191(7)nm,c=1.15692(14)nm,α=96.395(2)°,β=92.9940(10)°,γ=90.3440(10)°,V=0.62477(11)nm3,Z=2,F(000)=308,Dc=1.585g·cm-3,最终偏差因子R1=0.0521,wR2=0.1282.该化合物的不对称单元由3个独立的分子4,5-二氮芴-9-酮、磷酸和水分子构成,氢键连接分子形成三维超分子化合物.     

Superionic phase transition in (NH4)2SeO4·2NH4HSeO4 single crystal at 378 K

Abstract

DTA, structural and electric conductivity investigations were made for (NH₄)₄H₂(SeO₄)₃ single crystals. A high-temperature phase transition at 378 K to a superionic phase was found. The phase is characterized by a high electrical conductivity (～4.10^?3 Ω^?1 cm^?1) and a low activation energy (0.11 eV).     

Detection of two internal magnetic fields in Fe3(PO4)2·4H2O

Mössbauer studies of Fe₃(PO₄)₂·4H₂O (T_c = 15°K) show two effective hyperfine fields having magnitudes 362 kG and 203 kG. All other parameters describing the hyperfine and quadrupole interactions are given including the electric field gradients and relative orientations.