Spectra analysis of Tm in K2YF5

Emission and absorption spectra of Tm³⁺ in single crystal K₂YF₅ with different concentrations are reported and analyzed. The non-exponential feature of the fluorescence decay of ¹D₂ level for the high concentration sample indicates the existence of a cross-relaxation process. Energy level simulation has been carried out by using a phenomenological model with 16 parameters accounting simultaneously for the free ion and crystal field (CF) effects. A good fit was achieved with a root mean square deviation σ=18 cm⁻¹. The free ion and CF effects were then discussed by comparing the available data of K₂YF₅:Nd³⁺, LiYF₄:Tm³⁺ and LiYF₄:Nd³⁺.     

Absorption spectra of Cu2+ in azurite

EPR and optical absorption studies in azurite have been carried out at room and low temperatures. The EPR spectrum reveals that the ground state for Cu²⁺ ion is ²B₁. Peak to peak linewidth of EPR spectrum is calculated (ΔH_p = 76 G) and found to be close with the observed value. The Cu²⁺ ion situated in D_4h symmetry with spin-orbit interaction exhibits bands at 11,806, 16,484, 17,952 and 19,793 cm^?1. The tetragonal field parameters are calculated to be Ds = ? 3364 cm^?1 and Dt = ? 604 cm^?1. The crystal field splitting parameter is found to be Dq = ? 1175 cm^?1.     

Energy levels and crystal-field analysis of Tm in YAl3(BO3)4 crystals

The electronic structure of the Tm³⁺ in YAl₃(BO₃)₄ crystals has been investigated by means of low temperature absorption and emission spectroscopy in the 5000-30,000 cm⁻¹ range. The assignment of the lines composing the observed manifolds to transitions between the Stark levels of Tm³⁺ is complicated by the presence of extra features having different origins. The energy levels scheme of the doping ion has been compiled after a careful analysis of the spectra by reproducing the observed transitions by means of theoretical calculations based on a Hamiltonian, including the free ion and the crystal field (CF) terms. The agreement between experimental and calculated energy values was reasonably good, the overall r.m.s. deviation being 16 cm⁻¹. The resulting CF parameters have been tabulated and compared with those reported in literature for other rare earth ions doped in YAB. The analysis of trends observed along the lanthanide series evidences some inconsistencies and the necessity of a systematic investigation of these systems.     

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.     

Absorption spectra and Zeeman effects of Tm3+ in CaF2

The absorption spectra of Tm³⁺ in CaF₂ were analyzed by the concentration series method at 4·2^°K. Systems of lines, belonging to Tm³⁺ion centers of different structure, are isolated from the general spectra. Some of structures of Tm³⁺ ion centers were made clear by studying optical Zeeman effects and a change of absorption lines during thermal treatment. The tetragonal crystal field parameters and g-value of the upper state are also discussed.     

Analysis of the optical spectrum of Ho3+ in LiYF4

The energy levels for Ho³⁺ in single crystal LiYF₄ from 0–21,300 cm^?1 have been determined from polarized absorption and fluorescence spectra using crystals at temperatures between 4 and 300°K. Energy level assignments were made initially by comparing the crystal spectra with energy levels calculated by using crystal field parameters interpolated from previously reported analyses of Nd³⁺, Er³⁺ and Tm³⁺ in LiYF₄. The energy level scheme identifies energy levels in the 10 lowest J-multiplets and gives calculated energies for the next six higher J-multiplets. The crystal field parameters were varied to obtain a best fit between experimental and theoretical energies, and the final values B₂₀ = 410, B₄₀ = ? 615, B₄₄ = 819, B₆₀ = ? 27.9 and B₆₄ = 677 ± i32.8 cm^?1 give an r.m.s. fit of 2.78 cm^?1. The calculations were made by diagonalizing the crystal field Hamiltonian, H_x = Σ_kmB_kmC_km, in the space of ten lowest J-multiplets spanned by intermediate coupled free-ion wavefunctions calculated using the free-ion parameters of Carnall et al. for Ho in aqueous solution. The calculated g_∥ for the Γ_3.4 ground state of 13.63 compares favorably with a previously reported value of 13.3 ± 0.1.     

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.     

Electron paramagnetic resonance of Dy3+ in cubic ZnSe and Tm3+ in hexagonal CdS single crystals

Electron paramagnetic resonance has been observed for Dy³⁺ in ZnSe and Tm³⁺ in CdS. For Dy³⁺ doped ZnSe, an isotropic spectrum was observed having well resolved hyperfine lines due to ¹⁶¹Dy and ¹⁶³Dy. The g value obtained was 6.577 ± 0.002 and ¹⁶¹A was 191 ± 1 × 10⁴ cm^?1 and ¹⁶³A was 265 ± 3 × 10^?4 cm^?1. The agreement of the observed g value to g(τ₆) = 6.667 and the point-charge calculations suggest that Dy³⁺ occupies an interstitial (II) site with no local charge compensation. For Tm³⁺ doped in hexagonal CdS, an axial spectrum consistent with g_⊥ = 0, g_∥ = 10.722 ± 0.007, D = 2.57 GHz (crystal field splitting) and ¹⁶⁹A = 1207 ± 5 × 10^?4cm^?1. The large g_∥ value indicates that the Tm ion exits in the trivalent state. This is in reasonable agreement with previous reports of the non-Kramer's state of Tm³⁺.     

Light-induced charge transfer processes in Mn-doped Bi12GeO20 and Bi12SiO20 single crystals

The optical absorption and ESR spectra of Bi₁₂GeO₂₀ and B₁₂SiO₂₀ doped with Mn have been measured before and after illumination with visible light. Uniaxial stress measurements on a sharp line observed at 8026 cm^?1 were performed. The observed ESR spectrum is a superposition of six lines resulting from the hyperfine interaction of manganese ions in tetrahedral positions. The g-factor and hyperfine constant are g = 1.999 ± 0.003 and A = 78 Gs. Analysis of the light-induced absorption spectrum leads to the conclusion that a small hole polaron bound to an Mn impurity at a tetrahedral site is responsible for the very broad absorption band which appears after illumination. The sharp line is interpreted as due to a transition inside the Mn⁺ center in tetrahedral coordination. Bands in the region 10,000–16,000 cm^?1 are due to Mn³⁺ centers in interstitial positions, whose symmetry can be treated to a first approximation as tetragonal. The following crystal field parameters for this center were found: B = 565 cm^?1, Dq = 1400 cm^?1, Dt = ?330 cm^?1, Ds = 4170 cm^?1 and C = 2260 cm^?1. The illumination conditions which are needed for homogeneous coloration of the sample are also discussed.     

Analysis of the ν3 and ν1 infrared bands of GeH4

The high-resolution infrared spectrum of GeH₄ in the region 2020 to 2200 cm^?1 was analyzed. Most of the observed lines were assigned to transitions of the ν₃ and ν₁ bands of the five naturally occurring isotopic species. The spectrum was fitted by diagonalizing the v₃ = 1 and v₁ = 1 Hamiltonians coupled by the dominant vibration-rotation interaction term. For each isotopic species, about 100 transitions were fitted with an overall standard deviation of 0.006 cm^?1, using only 10 adjustable parameters. The five sets of parameters obtained are consistent with the expected isotope effects.     

Absorption spectrum of Cr3+ ion doped in lithium ammonium sulphate single crystal

The absorption spectrum of Cr³⁺ ion doped in lithium ammonium sulphate single crystal has been studied both at room (300 K) and liquid nitrogen (77 K) temperatures. From the nature and position of the observed bands, O_h symmetry is assumed for the ion. The spectroscopic parameters derived for the ion in the crystal at 77 K are Dq = 1655 cm^?1, B = 735 cm^?1 and C/B = 4.4     

Fourier transform spectroscopy on the 3ν2, 2ν2 + ν6 and ν3 + ν5 bands of H2CO

Fourier transform spectra covering the range from 1500 to 5400 cm^?1 with 0.02-cm^?1 resolution have been obtained for formaldehyde. A study of the region above 4000 cm^?1 has yielded rotational constants and other asymmetric rotor parameters for three bands: 3ν₂ (ν₀ = 5177.7611 ± 0.0005 cm^?1)2ν₂ + ν₆ (ν₀ = 4734.193 ± 0.004 cm^?1), and ν₃ + ν₅ (ν₀ = 4335.102 ± 0.001 cm^?1). An analysis of the A-type Coriolis interaction between the 2ν₂ + ν₆ state and the unobserved 2ν₂ + ν₄ state has yielded partially deperturbed rotational constants for the 2ν₂ + ν₆ state. Vibration-rotation interaction constants have been obtained for the ν₂ and ν₆ normal modes by combining the present results with those of previous workers.     

High resolution infrared spectrum of CH3Br: The ν4 band near 3100 cm−1

A Fourier transform spectrum (resolution 0.005 cm^?1) of the ν₄ band of methyl bromide has been analyzed. More than one thousand lines have been assigned for each isotopic species CH₃⁷⁹Br and CH₃⁸¹Br. A perturbation is apparent mainly near KΔK = 5. It was interpreted as due to a Coriolis interaction with ν₃ + ν₅ + ν₆. The whole spectrum is reproduced with a standard deviation smaller than 10^?3 cm^?1. Finally, the “hot” band ν₄ + ν₃ ? ν₃ has been assigned and analyzed.     

The vibration-rotation HDO absorption spectrum between 8558 and 8774 cm−1

The absorption spectrum of HDO has been recorded in the region 8558–8774 cm^?1 using a high-sensitivity intracavity F₂^?:LiF center laser spectrometer. The absorption sensitivity is 10^?7 cm^?1 and the line-center determination accuracy is about 4 × 10^?2 cm^?1. The spectrum was interpreted and the absorption lines were attributed to the ν₂ + 2ν₃ band of HDO. Energy levels up to J = 12 and rotational and centrifugal parameters of the vibrational (012) state were obtained.     

Energy levels,luminescence and electronic structure of ZnS:Tm3+

Energy levels, densities of states, electronic densities, electrostatic interaction integral parameters F_k and spin-orbit coupling parameters ζ_4f for ZnS: Tm³⁺ are calculated self-consistently, using both one-electron local density discrete variational non-relativistic Hartree-Fock-Slater (HFS) and relativistic Dirac-Slater (DS) cluster models. In these calculations, both spin-restricted and spin-polarized models are considered. The finite clusters calculated include TmS₄ and TmS₄Zn₁₂ clusters for cubic ZnS, which are embedded in the crystal environment. The spin-orbit coupling parameter ζ_4f derived from DS cluster calculations is equal to 2689 cm^-1, rather near the result of the relativistic Hartree-Fock free ion model. The parameters F_k and ζ_4f are further calculated from the 4f radial wave function obtained by solving the HFS and the DS atomic equations. It is shown that by decreasing the effective exchange-correlation potential, these parameters can be reduced to approximately match empirical values. A comparison of the excited energy level scheme of ZnS:Tm derived from the calculated parameters and the experimental spectra is presented.     

A high-resolution study of the ν7 band of propyne

The infrared spectrum of propyne (methyl acetylene) between 1300 and 1620 cm^?1 has been reanalyzed at a resolution of 0.006 cm^?1. The main Fermi and Coriolis interactions of the ν₇^±1 band have been identified, as has the Fermi interaction between (ν₈ + ν₁₀)⁰ and ν₄⁰. Reassignment of a subband shows that ν₄⁰ has a very small transition moment. Thirty-eight molecular parameters for the interacting excited vibrational levels were determined by a least-squares analysis of 1550 lines.     

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.     

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.     

Dielectric properties and temperature stability of BaTiO3 co-doped La2O3 and Tm2O3

The influence of La₂O₃ and Tm₂O₃ co-doping on the dielectric properties and the temperature stability of BaTiO₃ was investigated. BaTiO₃ ceramics were prepared with the compositional formula of (Ba_1−xLa_x)(Ti_1-x/4−yTm_y)O₃. La₂O₃ and Tm₂O₃ co-doping in BaTiO₃ mainly had effects on an increase in the dielectric constant and the temperature stability, respectively. The increase of La₂O₃ concentration and the decrease of Tm₂O₃ concentration in BaTiO₃ resulted in a decrease of lattice parameter and tetragonality because La³⁺ ion substituting for Ba site is smaller than Ba²⁺ ion and Tm³⁺ ion substituting for Ti site is larger than Ti⁴⁺ ion. With the increase of La₂O₃ and the decrease of Tm₂O₃, the dielectric constant of BaTiO₃ was enhanced in spite of the reduction of tetragonality. P-E hysteresis measurements revealed that this phenomenon was based on the improvement of remanent polarization with the increase of La₂O₃ concentration. The introduction of excess Tm₂O₃ in BaTiO₃ suppressed the grain growth and BaTiO₃ ceramics showed higher temperature stability due to the stable tetragonal structure and the small grain size with the increase of Tm₂O₃ concentration.     

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.

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