Fourier transform spectroscopy of the A3Π-X3Σ− transition of NH

The A³Π-X³Σ⁻ transition of NH has been observed using a high-resolution Fourier transform spectrometer. The first three vibrational levels in each state were observed and the vibrational, fine structure, and rotational constants obtained.     

High-resolution spectroscopy of the a4Σ−3/2 − X12Π3/2 system of gold monosulphide in the near infrared

ABSTRACT

We have recorded the a⁴Σ^? _3/2 ? X₁ ²Π_3/2 (0,0), (1,0), and (2,0) bands of gaseous gold monosulphide (AuS) at sub-Doppler resolution in the near-infrared region. The molecules were made in a hollow cathode discharge source by the reaction of sputtered gold with carbonyl sulphide. The high resolution of the laser excitation spectrum enabled the determination of molecular constants describing the rotational and ¹⁹⁷Au hyperfine structure in both states, as well as the spin–rotation interaction in the a⁴Σ^? _3/2 state. The natures of the two electronic states are discussed in the context of the observed hyperfine structure.     

Magnetic properties of Nd3+ in Nd−Ba−Cu−O-compounds

Neutron diffraction, neutron spectroscopy and magnetization measurements have been employed to study the structural, electronic, and magnetic behavior of eleven compounds with the general formula Nd_1+y Ca _v Ba_2–y–v Cu₃O _x (0y0.5; 0v0.25; 6x7). The structure turned out to react to oxygen reduction similar as other 123-compounds, yielding discontinuities close to the metal-insulator-transition and the well-known relations of bond lengths as a function ofT _c. The crystalline electric field (CEF) interaction, splitting the 10-fold degenerate ground-state J-multiplet of the Nd³⁺-ions into five doublet states, was investigated by neutron spectroscopy. The derived CEF parameters have been used to determine changes in the electronic surroundings of the Nd³⁺ ions. In addition, with the help of the CEF parameters the thermodynamic magnetic properties of these compounds were calculated which turn out to be in good agreement with the experimental data.     

Electron paramagnetic resonance study of S− and S− 3

Abstract

Two new sulphur are reported in monocristalline rubidiumchloride doped with rubidium and sulphur, and irradiated with X-rays at room temperature. By an extensive comparison with other experimental data on chalcogen centres in alkali halides an interstitial RbCl:S^? and a substitutional RbCl:S^? ₃ model is proposed for these paramagnetic defects. Theoretical calculations confirm the S^? ion model for the former.     

High-resolution infrared Fourier transform spectroscopy of SO in the X3Σ− and a1Δ electronic states

The v = 1 ← 0 vibration-rotation absorption bands of ³²S¹⁶O, ³⁴S¹⁶O, and ³²S¹⁸O in the ground electronic state, X³Σ⁻, and the v = 1 ← 0 vibration-rotation band of ³²S¹⁶O in the first excited electronic state, a¹Δ, were measured at 0.004 cm⁻¹ unapodized resolution with a high-resolution Fourier transform spectrometer coupled to a long path absorption cell. The v = 2 ← 0 vibration-rotation band of ³²S¹⁶O in the X³Σ⁻ state was also observed. Line positions for P- and R-branch transitions up to N = 44 for ³²S¹⁶O have been measured and analyzed yielding improved molecular parameters. The present measurements are compared with previous infrared and microwave measurements.     

Synthesis and ionic conduction of C3A-type nasicon Na3+3x−yY1−xSi3−yPyO9

In the solid solutions of Na_3+3x−yY_1−xSi_3−yP_yO₉, new fast Na⁺ -conductors were obtained. The ionic conductivity, σ, and the activation energy, E, of the most conductive material, Na_4.425Y_0.375Si_2.55P_0.45O₉ were 5 × 10⁻³ S/cm at 300°C and 10 kcal/mol, respectively. Those values were strongly dependent upon the composition. With an increase of Na concentration, [Na], σ increased and E decreased. Accommodation of higher [Na] in the structure was madefeasible by decreasing [Y] and increasing [P]. Based on the crystal structure assumed for Na_3+3x−yY_1−xSi_3−yP_yO₉ and on the above results, a conduction model was presented. The structural consideration revealed that a conduction path is formed along the 〈1 1 1 〉 direction, where Y³⁺ ions locate in the way of Na⁺ ions.     

The laser-induced fluorescence spectroscopy of gold monoxide: B2Σ−－X2Π3/2 transition

The electronic spectrum of the gaseous gold monoxide molecule has been investigated in the range of 16000－18500?cm^?1 using laser induced fluorescence spectroscopy and single vibronic level emission spectra. Five rotationally resolved vibronic bands are observed and assigned to the transitions B²Σ^? (v'?=?0－4) －X²п_3/2 (v''?=?0), in which the 0－0 transition is observed for the first time. The molecular constants of the excited state B²Σ^? are obtained by a rotational analysis of the spectra. The spin-orbit coupling constant and the vibrational constants of the ground state X²п_i are determined with the accuracy improved by one order of magnitude. The lifetimes of most observed bands are also measured for the first time.     

Influence of CO 3 2− and OH− groups on dielectric losses of NaCl crystals

The results of measuring the dielectric losses of NaCl crystals with a different concentration of Na₂CO₃ and NaOH admixtures in the melt are given in the present paper. From a comparison of the curves found for the dielectric losses of the crystals studied it can be seen that the course of tan and the positions of the relaxation maxima, corresponding to the measured specimens with CO ₃ ^2– or OH^– admixtures, hardly differ. From these measurements and from a comparison with the results of other authors it follows that the admixture is probably the same in both groups of crystals.In conclusion the author thanks Dr. A. Bohun for discussions on the results and for his continuous interest in this work.     

A computational study of the electron detachment energies of Al2As2 − and Al3As3 −

Ab initio and density functional theory calculations are reported for the low-lying electronic states of Al₂As₂ ^?, Al₂As₂, Al₃As₃ ^?, and Al₃As₃. The ²B_2g ground electronic state of Al₂As₂ ^? has a rhombic structure with the Al atoms occupying the shorter diagonal. In contrast, the As atoms occupy the shorter diagonal of the ground state rhombic structure of Al₂As₂. Electron detachment energies computed for Al₂As₂ ^? are presented and discussed. The adiabatic electron affinity of Al₂As₂ ^? is calculated to be 2.1 eV at the CCSD(T) level, using B3LYP and MP2 optimized geometries. The ground states of both Al₃As₃ ^? (²A₁′) and Al₃As₃ (¹A₁′) have planar hexagonal D_3h geometry. Electron detachment energies computed for the anion are reported. At the CCSD(T)//B3LYP level, the electron affinity of Al₃As₃ is calculated to be 2.47 eV.     

An intermodulated fluorescence study of the A2Σ−-X2Πi band system of copper monoxide

Several lines in the A²Σ⁻(v = 0)-X²Π_i(v = 0) visible band system of gas phase copper monoxide have been measured at sub-Doppler resolution using the technique of intermodulated fluorescence. The copper nuclear magnetic hyperfine splitting is clearly resolved. The observations were fitted to an effective Hamiltonian model and values of the magnetic hyperfine parameters of b_F = −0.0302 cm⁻¹ for the A state and d = 0.0024 cm⁻¹ for the X state were determined. An interpretation of these values in terms of the proposed electronic configurations of these states is presented.     

Structural and superconducting properties of Eu1−xPrxBaSrCu3O7−δ

We have investigated the structural and superconducting properties of Eu_1−xPr_xBaSrCu₃O_7−δ by X-ray diffraction analysis, AC and DC magnetization and DC resistivity measurements. The parent compound crystallizes in the orthorhombic symmetry which transforms to tetragonal symmetry at x=0.2. Superconducting transition temperature T_c decreases monotonically with increasing x which approaches zero at x=0.6. The enhancement in critical concentration x_cr observed in Eu_1−xPr_xBa₂Cu₃O_7−δ on replacing 50 at.% Ba by Sr is attributed to the resulting local structural changes.     

Rotational analysis of the a3Π-X1Σ+ bands of GaD

A new method of producing strong and clean emission spectra of the gallium hydride/deuteride molecule has been developed. Five bands belonging to the gallium deuteride molecule (GaD) have been photographed under high resolution. The rotational analyses of the bands lying at 5669.14 Å (0-0) and 5675.10 Å (1-1) in the a³Π₁-X¹Σ⁺ transition, 5761.0 Å (0-0) and 5766.20 Å (1-1) in the a³Π_0⁺-X¹Σ⁺ transition, and 5760.85 Å (0-0) in the a³Π_0⁻-X¹Σ⁺ transition have been performed. Accurate rotational constants (B, D) have been determined for the X¹Σ⁺, a³Π_0^± and a³Π_1^± states. The Λ doubling in the a³Π₀ (v = 0) and a³Π₁ (v = 0 and 1) states are obtained.     

A simulation study of vibrational relaxation of I− 3 in liquids

The temperature dependence of the vibrational relaxation of a flexible model of triiodide in a Lennard-Jones solvent (xenon) has been studied using equilibrium molecular dynamics simulations. The internal dynamics of the ion is calculated from a previously published semi-empirical valence bond model with a limited number of basis states. Vibrational decorrelation rates of the symmetric and antisymmetric stretching modes were found from the time correlation functions of the normal coordinate velocities and the vibrational energy relaxation rates from the time correlation functions of the kinetic energy in each mode. The vibrational dephasing rates and the energy relaxation rates decrease slowly as the temperature is lowered and do not show a discontinuity when the fluid solidifies, although the reorientational diffusion rates change rapidly at low temperatures. In order to interpret the results, perturbation theory expressions for the relaxation rates were evaluated for simulations of a rigid model of the ion and found to agree well with the direct observations. These showed that, unusually, both the solvent force and its derivative, the solvent potential curvature, contribute to the dephasing of the symmetric mode. The relevant fluctuation correlation times are very short, which may explain the insensitivity of the vibrational relaxation to the state of the solvent.     

On the rotational intensity distribution in the a1Δg → X3Σg− magnetic dipole transition of oxygen molecule

The relative intensity distribution in the rotational structure of the a¹Δ_g → X³Σ_g⁻ magnetic dipole transition of molecular oxygen is examined. Use is made of experimental data obtained from the high-resolution (0.02 cm⁻¹) FTS recording of the 0-0 band published by C. Amiot and J. Verges (Canad. J. Phys. 59, 1391–1398 (1981)). Comparison of the experimental and theoretical intensities indicates that rotational linestrength formulas containing purely vibronic transition moments are inadequate and need to be supplemented by two additional parameters of rovibronic origin.     

Potential energy functions for the ground state X3Σ- and excited state 1Σ+ of UO

Based on group theory and atomic and molecular reactive statics (AMRS), the ground state X³Σ^? and excited state ¹Σ⁺ of UO and their reasonable dissociation limits are derived successfully. Using the MP2 method with the relativistic e? ective core potential and valence electron basis set (5s4p3d4f)/[3s3p2d2f] for the U atom and basis set 6-311G* for the O atom, the present work has calculated the potential energy curves for the ground state Χ³Σ^? and excited state ¹Σ⁺ of UO. The equilibrium distance and dissociation energy are 0.1833 nm and 6.9241 eV for the Χ³Σ^? state, and 0.1825 nm and 8.8756eV for the ¹Σ⁺ state. Spectroscopic data are derived for the first time.     

Magnetic behavior of the alloys CeCuyGa4−y and Ce1−xLaxCuGa3

The results of magnetic susceptibility (x), electrical resistivity (ρ) and heat-capacity (C) measurements of the alloys CeCu_yGa_4−y (y = 0.5, 1.0, 1.25 and 1.5) and Ce_1−xLa_xCuGa₃ (x = 0.2 and 0.9), crystallizing in the BaAl₄-type tetragonal structure, are reported. The Kondo effect tends to dominate with increasing y. All the data for the y = 0.5 alloy are consistent with the onset of ferromagnetic ordering at 6 K. For y = 1.0 and 1.25, though ρ gradually drops below 6 K, the C data do not show the existence of magnetic ordering above 2 K; presumably, for y = 1.0, 1.25 and 1.5, long-range magnetic ordering sets in below 2 K. Above all, C tends to increase with decreasing temperature before the onset of long range magnetic ordering and the values of C/T per Ce mol are considerably diminished for x = 0.9. It is proposed that this C/T enhancement lies in the magnetic precursor effects and not on the heavy-fermion behaviour.     

Optical properties of Li1−xNb1−xEu2xO3 solid solutions

Abstract

The effects of europium substitution on crystalline solubility, structural changes and optical properties of LiNbO₃ is reported. Li_1?xNb_1?xEu_2xO₃ solid solutions exist over a very limited range of europium concentrations (x ≤ 0.01). The solid solutions were characterized by X-ray powder diffraction and density measurements. Within the range of compositions of the solid solutions, the optical properties (emission and excitation spectra) of the Eu³⁺ ions have been characterized. The obtained optical data indicate that two equally abundant europium luminescent species exist in the stoichiometric speciments; these correspond to the Eu³⁺ ions occupying the Li⁺ and Nb⁵⁺ sites, in agreement with the replacement mechanism which is inferred from density measurements. Other Eu³⁺ luminescent species which appear to be closely related with lithium deficiency were found to exist in nonstoichiometric samples, in addition to those which are present in the stoichiometric materials.