Absorption spectra of Cu2+ in shattuckite and plancheite

Optical and EPR measurements are carried out on shattuckite, a copper bearing silicate. The EPR spectrum observed at 120 K reveales hyperfine structure for parallel and perpendicular components. The measured values are g6 = 2.402, g⊥ = 2.038, A6 = 112 × 10^-4 cm^-1 and A⊥ = 49.5 × 10^-4 cm^-1 and they indicate a tetragonal distortion for the Cu²⁺ion. Further, the constants P and K are evaluated and found to be 0.014 cm^-1 and 0.0112 respectively. The bands observed at 8160, 13330 and 16125 cm^-1 are assigned to the electronic states of Cu²⁺, in a crystal field subjected to tetragonal (C_4V) distortion. The crystal field parameters evaluated are Dq = -1333, Ds = -1565 and Dt = -380 cm^-1. Correlating the EPR and optical data, the orbital reduction factors are calculated as k6 = 0.89 and k⊥ = 0.59. It is confirmed from EPR and optical studies that the Cu²⁺ion in shattuckite is sited in an elongated octahedron. Similar studies are carried out for plancheite. The observed optical absorption spectrum of plancheite is attributed to Cu²⁺ sited in an elongated octahedron and tetragonal field parameters are evaluated.     

The potential barrier height for a Jahn-Teller center

The EPR spectrum of the Cu²⁺ ion in a ZnSiF₆·6H₂O crystal is studied in the temperature range T=5?300K. It is shown that the EPR spectrum can be represented in the form of a superposition of three contributions with essentially different properties. The first contribution is characterized by the maximal intensity at low temperatures and is described by a spin Hamiltonian with a large anisotropy of parameters. The second contribution has the maximal intensity at high temperatures and is described by a spin Hamiltonian with a low anisotropy of parameters. The third contribution cannot be described by a spin Hamiltonian and has the form of a partly orientationally averaged EPR spectrum. The reason for the emergence of these contributions is substantiated along with the form of the temperature dependence of their intensities on the basis of variation of the populations of vibronic states upon a change in temperature. The height (E₀=4±1cm_?1) of the potential barrier separating three equivalent Jahn-Teller potential wells of the Cu²⁺ ion is determined from analysis of the temperature dependence of the integrated intensity of the EPR spectrum. The obtained value of the barrier height substantially differs from the estimate (100 cm^?1) obtained earlier [2, 3] for the Cu²⁺ ion in ZnSiF₆·6H₂O on the basis of the tunneling model. It is shown that the forms of the temperature dependences of the linewidth of the low-and high-temperature EPR spectra are essentially different. This difference indicates that the contributions of the low-and high-temperature EPR spectra are associated with quantum-mechanical transitions between these states. It is proposed that the low-and high temperature contributions to the EPR spectrum are associated with the filling of under-the-barrier and above-the-barrier vibronic states, respectively.     

EPR study of Fe3+ and Mn2+ in CeO2 and ThO2

Attempts were made to grow CeO₂ and ThO₂ single crystals doped with transition metal ions. Only Fe³⁺ and Mn²⁺ could be detected by the EPR technique. The EPR spectrum of Fe³⁺ in CeO₂ exhibits the well-known fine structure in cubic fields. The parameters areg=2.0044(1) anda=15.6(1)·10^?4 cm^?1. The hyperfine constantA for⁵⁷Fe in hexahedral coordination was found to be 8.9(1)·10^?4 cm^?1. The EPR spectrum of Mn²⁺ in CeO₂ reveals two cubic Mn²⁺ centers. The parameters for center 1 areg=1.9999(1) andA=86.9(1)·10^?4 cm^?1 and for center 2g=1.9984(1) andA=87.0(1)·10^?4 cm^?1. Heating the Mn doped CeO₂ samples in hydrogen, the Mn²⁺ centers transform from cubic into trigonal centers with approximate values ofg=1.9988(2),A=84.5(6)·10^?4 cm^?1 andD=203(1)·10^?4 cm^?1. The two observed Mn²⁺ centers in ThO₂ exhibita priori axial symmetry with approximate values ofg=2.0006(2),A=88.9(4)·10^?4 cm^?1 andD=33(3)·10^?4 cm^?1.     

Absorption spectrum of Cs2Mg(SO4)2 · 6H2O:Ni2+ single crystals

The absorption spectrum of Ni²⁺ doped in Cs₂Mg(SO₄)₂ · 6H₂O single crystals has been studied at room and liquid nitrogen temperatures in the range 7000–34000 cm^?1. The observed spectrum is satisfactorily interpreted in terms of cubic ligand field model including spin-orbit coulping. The ligand field parameters evaluated to best fit the observed spectrum are B = 955 cm^?1, C = 3572 cm^?1, Dq = 910 cm^?1 and ξ = 550 cm^?1. The non-ligand field band observed at 77K has been interpreted to be the superposition of vabrational mode of SO₄^2? radical on ₃T_1g(F) band.     

EPR identification of the iron charge transfer in CuAlS2:Fe

The EPR spectrum of Fe²⁺ has been observed in CuAlS₂. It consists of a single line with g^eff₆ ≈ 9.5 at 34.8 GHz. An analysis yields the following crystal field parameters: 10Dq ≈ 3600 cm^?1, μ ≈ 800 cm^?1 and δ ≈ 900 cm^?1. It is found that Fe³⁺ can be converted into Fe²⁺ by irradiation with light of energies considerably less than the band gap. These results directly confirm the charge transfer model previously suggested for CuAlS₂:Fe.     

The torsional spectrum of chlorine nitrate

The far-infrared torsional spectrum of ClONO₂ (chlorine nitrate) was reexamined at 0.06-cm^?1 apodized resolution. The torsional spectrum consists of a single, regularly spaced series of Q branches at 122.56 ? 2.422 v′ + 0.0296 v′² cm^?1. Chlorine nitrate is planar with torsional potential constants V₂ = 1900 ± 100 cm^?1 and V₄ = 90 ± 50 cm^?1. The torsional partition function is calculated at room and stratospheric temperatures.     

EPR study of the Ag6S3O4 compound prepared by two methods

The temperature dependence of the EPR spectra of the recently discovered Ag₆S₃O₄ phase in the Ag-O-S system prepared by two methods, the known method of co-precipitation from aqueous solution and a new method depending on the interaction of Ag₂S and Ag₂SO₄ solid reagents, has been investigated. No EPR spectra were observed at room temperature, while at liquid helium temperature a number of EPR spectra have been recorded, which disappeared upon increasing temperature up to liquid nitrogen temperature. The sample obtained by the co-precipitation method revealed an intense, rich EPR spectrum that has been tentatively interpreted assuming the presence of at least two different Ag²⁺ ion complexes, one monomer resulting in an intense anisotropic, rhombic EPR powder pattern with g₁ = 1.93(1), g₂ = 2.025(3), g₃ = 2.094(5), hyperfine constants A₁ = = A₂ = 60(5) · 10^?4 cm^?1,A ₃ = 90(5) · 10^?4 cm^?1 and one dimer EPR pattern presumably involving a pair of Ag²⁺ ions with internuclear separation of 4.3 Å. However, the presence of larger clusters could not be excluded. On the other hand, the sample obtained by a solid state reaction method has given rise to two rather weak EPR lines centered at g_eff = 2.105(3) and g_eff = 4.213(3), respectively.     

ESR and optical study of Cu2+-doped bis-(5,5′-diethylbarbiturato)bis picoline Zn(II)

ESR studies were conducted on Cu²⁺-doped bis-(5,5′-diethylbarbiturato)bis picoline Zn(II). Two Cu²⁺ lattice sites, Cu²⁺(I) and Cu²⁺(II), were identified. These sites exhibit two sets of four hyperfine lines in all directions. The g factor and hyperfine splitting were calculated from ESR absorption spectra: g_x ?=?2.0201?±?0.002, g_y ?=?2.0900?±?0.002, g_z ?=?2.1634?±?0.002, A_x ?=?(30?±?2)?×?10^?4?cm^?1, A_y ?=?(40?±?2)?×?10^?4?cm^?1 and A_z ?=?(154?±?2)?×?10^?4?cm^?1. It was found that Cu²⁺ enters the lattice substitutionally. The ground-state wavefunction of the Cu²⁺ ion in this lattice was determined from the spin Hamiltonian constants obtained from the ESR studies. With the help of an optical absorption study, the nature of the bonding in the complex is also discussed.     

EPR and Optical Absorption Study of Cr3+-Doped Dipotassium Tetrachloropalladate

X-band electron paramagnetic resonance (EPR) study of Cr³⁺-doped dipotassium tetrachloropalladate single crystal is done at liquid nitrogen temperature. EPR spectrum shows two sites. The spin-Hamiltonian parameters have been evaluated by employing hyperfine resonance lines observed in EPR spectra for different orientations of crystal in externally applied magnetic field. The values of spin-Hamiltonian and zero-field splitting (ZFS) parameters of Cr³⁺ ion-doped DTP for site I are: g _x  = 2.096 ± 0.002, g _y  = 2.167 ± 0.002, g _z  = 2.220 ± 0.002, D = (89 ± 2) × 10^?4 cm^?1, E = (16 ± 2) × 10^?4 cm^?1. EPR study indicates that Cr³⁺ ion enters the host lattice substitutionally replacing K⁺ ion and local site symmetry reduces to orthorhombic. Optical absorption spectra are recorded at room temperature. From the optical absorption study, the Racah parameters (B = 521 cm^?1, C = 2,861 cm^?1), cubic crystal field splitting parameter (Dq = 1,851 cm^?1) and nephelauxetic parameters (h = 2.06, k = 0.21) are determined. These parameters together with EPR data are used to discuss the nature of bonding in the crystal.     

Cu+ ion conductivity of K2Cu(CNS)3

K₂Cu(CNS)₃ is found to be a Cu⁺ ion conductor with a room temperature (30°C) conductivity of ～5×10^?3ω^?1 cm^?1. The phase structure of the CuCNS + KCNS system and data on temperature variation of the conductivity of K₂Cu(CNS)₃ is reported. The related compound KAg(CNS)₂ is found to be a Ag⁺ ion conductor.     

EPR and Magnetic Susceptibility of Na2O–CuO–P2O5 Glasses

Abstract

(50?x/2)Na₂O–xCuO–(50?x/2)P₂O₅ glasses (x=1, 5, 15, or 30 mol%) have been prepared and characterized by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The shape of the Cu²⁺ EPR spectrum depends on the Cu content, and the corresponding computer simulations suggest that the Cu²⁺ ions occupy two different sites in these glasses: one of them is preponderant at low Cu content and the other is preponderant at high content, in which the Cu²⁺–Cu²⁺ interactions are more important. From EPR parameters, it was found that for the site at low content, the covalency of copper ion bonding with the surrounding ligands is appreciable. The magnetic susceptibility data appear to follow the Curie–Weiss law (χ=C/(T?θ_p)) with negative paramagnetic Curie temperature θ_p indicating antiferromagnetic interactions between Cu²⁺ ions that are more significant in the samples with high Cu content, in agreement with EPR results.     

Absorption spectrum of Cu2+ in strontium tartrate tetrahydrate

The absorption spectrum of the single crystals of Cu²⁺ in strontium tartrate tetrahydrate, grown from silica gel, is studied at laboratory and liquid nitrogen temperatures. From the analysis of the spectrum, the following crystal field parameters are evaluated, Dq = 1000 cm^?1, Ds = 1535 cm^?1 and Dt = 490 cm^?1.     

EPR and optical studies of Cu doped ammonium dihydrogen phosphate single crystals

Electron paramagnetic resonance (EPR) spectra of Cu²⁺ ion in ammonium dihydrogen phosphate are studied at liquid nitrogen temperature (77 K). Four magnetically inequivalent Cu²⁺ sites in the lattice are identified. The angular variation spectra of the crystal in the three orthogonal planes indicate that the paramagnetic impurity, Cu²⁺ enters the lattice substitutionally in place of NH₄⁺ ions. The spin Hamiltonian parameters are determined with the fitting of spectra to rhombic symmetry crystalline field. The ground state wave function of Cu²⁺ ion is constructed and found to be predominantly |x²-y²〉. The cubic field parameter (Dq) and tetragonal parameters (Ds and Dt) are determined from optical spectra at room temperature. By correlating EPR and optical absorption spectra, the bonding coefficients are calculated and nature of bonding of metal ion with different ligands in the crystal is discussed.     

Optical absorption spectrum of Ni2+ ion doped in synthetic lecontite

The optical absorption spectrum of Ni²⁺ ion doped in lecontite (sodium ammonium sulphate dihydrate) single crystal has been studied at room and liquid air temperatures. All the bands could be assigned assumingO _h symmetry for the Ni²⁺ ion in the crystal. The splitting of³ T _1g (F) band at liquid air temperature has been attributed to spin-orbit interaction. The crystal field and spin-orbit parameters derived areD _q=1000 cm^?1;B=740 cm^?1;C/B=4.27 and ζ=600 cm^?1. All the bands observed show a blue shift when the crystal was cooled to liquid air temperature.     

Inverse Raman spectrum of the ν1-fundamental of CF4

We have obtained fully resolved spectra of the ν₁ (Q-branch) band of CF₄ at a pressure of 4 Torr using a variation of stimulated Raman spectroscopy. With an experimental resolution of ≤0.004 cm^?1, no detectable tensor splitting of the rotational levels exists up to J = 55. The spectrum is readily fit with a band origin α = 909.0720 cm^?1 and a single rotational term β ? β₀ = ?3.417 × 10^?1cm^?1. We have also observed an underlying hot band, which we tentatively assign as the ν₁ + ν₂ ← ν₂ transition, with α′ = 909.1997 cm^?1 and (β ? β₀)′ = ?3.405 × 10^?4cm^?1.     

Spin-spin interaction of Dy3+ ions in KY(WO4)2

The spin-spin interaction of Dy³⁺ ions in a KY(WO₄)₂ single crystal is investigated by electron paramagnetic resonance (EPR) spectroscopy at a temperature of 4.2 K and a frequency of 9.2 GHz. The EPR spectra of ion pairs located in different coordination shells are analyzed. It is revealed that the considerable contribution to the spin-spin interaction of the nearest neighbor ion pair nn is made not only by the magnetic dipole-dipole interaction but also by the isotropic exchange interaction with the parameter I _nn = (+601 ± 17) × 10^?4cm^?1. The exchange interaction in pairs of more widely spaced ions is substantially weaker: I _5n = (?38 ± 3) × 10^?4cm^?1 and I _9n = (+18 ± 4) × 10^?4cm^?1. For the other ion pairs, the magnetic dipole-dipole interaction dominates. It is found that the EPR spectra of single ions and ion pairs exhibit a superhyperfine structure associated with tungsten nuclei.     

Hyperfine and nuclear quadrupole interactions in copper-doped cadmium oxalate trihydrate single crystals

Electron spin resonance experiments on Cu²⁺ doped in a single crystal of cadmium oxalate trihydrate grown by a slow diffusion technique have been carried out at 77 K. The major features of the ESR spectra can be attributed to divalent copper (3d⁹) in substitutional Cd²⁺ sites. Information has been gained about the hyperfine and quadrupole interactions concerning the ion. The spin-Hamiltonian parameters in the $\text{S =}\text{1}\text{2}$, $\text{I =}\text{3}\text{2}$ manifold are: g_x = 2.0211; g_y = 2.2249; g_z = 2.4536; A_x = +84.5 × 10^?4cm^?1; A_y = +16.8 × 10^?4cm^?1; $\text{A}{}_{\mathrm{z}}\text{= ?40.8 × 10 ×}{}^{\mathrm{?4}}\text{cm}{}^{\mathrm{?1}}$; P_x = ?7.4 × 10^?4cm^?1; P_y = ?0.4 × 10^?4cm^?1; and P_z = +7.8 × 10^?4cm^?1. An evaluation of the asymmetry and quadrupole coupling parameters revealed that the ground state of the guest ion in Cd(COO)₂ · 3H₂O is 0.97|x² ?y₂ > +0.24 |3z² ? r² >.     

Action du champ cristallin sur l'ion Er3+ dans l'oxysulfure de terre rare Er2O2S

The Er³⁺ electronic ion structure, in its 4f¹¹ configuration, has been determined by the optical absorption spectrum of Er₂O₂S. By the use of the Slater parameters F₂ = 424,4, F₄ = 66,1, F₆ = 6,87 cm^?1 and the Spin-orbit parameter ζ = 2367 cm^?1, the experimental ‘free-ion’ energy levels have been fitted with a r.m.s. deviation of 78 cm^?1. In intermediate coupling, the crystal field parameters V₂⁰ = 90, V₄⁰ = 175, V₄³ = 2365, V₆⁰ = 0,5, V₆³ = 205 and V₆⁶ = 180 cm^?1 give the best fit with experimental data. For 56 Stark levels involved the calculation predicts the splittings with a r.m.s. deviation of 12 cm^?1. The magnetic susceptibility has been calculated and is in satisfactory agreement with experimental powder measurements.     

EPR, Optical Absorption and Superposition Model Study of Fe3+-Doped Ammonium Dihydrogen Phosphate Single Crystals

X-band electron paramagnetic resonance (EPR) studies are carried out on Fe³⁺ ions doped in ammonium dihydrogen phosphate (ADP) single crystals at room temperature. The crystal field and spin Hamiltonian parameters are evaluated from the resonance lines obtained at different angular rotations. The obtained values of spin Hamiltonian and zero-field parameters of the Fe³⁺ ion in ADP are: g = 1.994 ± 0.002, |D| = (220 ± 5) × 10^?4 cm^?1 and a = (640 ± 5) × 10^?4 cm^?1. On the basis of EPR data, the site symmetry of the Fe³⁺ ion in the crystal is discussed. The Fe³⁺ ion enters the lattice substitutionally replacing the NH₄ ⁺ sites. The optical absorption of the crystal is also studied at room temperature in the wavelength range of 195–925 nm. The energy values of different orbital levels are calculated. The observed bands are assigned as transitions from the ⁶ A _1g (S) ground state to various excited quartet levels of the Fe³⁺ ion in a cubic crystalline field. From the observed band positions, Racah interelectronic repulsion parameters (B and C), cubic crystal field splitting parameter (D _q ) and Trees correction are calculated. There values are: B = 970, C = 1,923, D _q  = 1,380 cm^?1 and α = 90 cm^?1, respectively. On the basis of EPR and optical data, the nature of bonding in the crystal is discussed. The zero-field splitting (ZFS) parameters are also determined theoretically using B _kq parameters estimated from the superposition model. The values of ZFS parameters thus obtained are |D| = (213 ± 5) × 10^?4 cm^?1 and |E| = (21 ± 5) × 10^?4 cm^?1.     

Optical absorption spectrum of VO2+ in calcium tartrate tetrahydrate

Single srystals of calcium tartrate doped with VO²⁺ are grown from silica gel. Its optical absorption spectrum is studied at laboratory and liquid air temperatures. The spectrum is analysed and ascribed to VO²⁺ ion in C_4v symmetry. The following crystal field parameters are evaluated.

$\text{Dq = 1835}\text{cm}{}^{\mathrm{?1}}\text{, Ds = ?1980}\text{cm}{}^{\mathrm{?1}}\text{, Dt = 1280}\text{cm}{}^{\mathrm{?1}}$