Electronic absorption spectrum of Ni2+ in lithium potassium sulphate single crystal

Single crystals of nickel-doped lithium potassium sulphate were grown by slow evaporation method at room temperature. From the nature and position of the bands observed, a successful interpretation of all the bands could be made assumingO _h symmetry for the Ni²⁺ ion in the crystal. The bands have been assigned transitions from the ground³A_2g(F) state to the excited³T_2g(F),¹E_g(D),³T_1g(F),¹T_2g(D) and³T_1g(P) states. The crystal field parameters derived areDq=910cm^–1,B=890cm^–1 andC=3560cm^–1.The authors wish to express their thanks to Prof. K. Sreerama Murthy for his constant encouragement throughout this investigation. The authors are also thankful to Prof. Mihir Chowdhury, Indian Association for the cultivation of Science, Calcutta for giving permission to take the spectra.     

Optical absorption spectrum of Ni2+ doped in ammonium zinc sulphate

The optical absorption spectrum of Ni²⁺ ion doped in ammonium zinc sulphate has been studied at room and liquid air temperatures. From the nature and the positions of the bands a successful interpretation of all the bands could be made assumingO _h symmetry for the Ni²⁺ ion in the crystal. The fine splitting of the³ T ₁ ¹ band at liquid air temperature has been successfully interpreted to be due to spin-orbit interaction. The crystal field and spin-orbit parameters derived areDq=1000 cm⁻¹;B=750 cm⁻¹;C=3.45B andξ=600 cm⁻¹.     

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.     

Optical absorption spectrum of Co2+ in ammonium perchlorate single crystal

Single crystals of cobalt — doped ammonium perchlorate were grown at room temperature. The electronic absorption bands observed at room and liquid air temperatures have been assigned transitions from the ground⁴T₁(F) state to the excited⁴T₂(F),⁴A₂(F),²T₁(G) and⁴T₁(P) states. The crystal parameters derived areDq=880 cm^–1,B=865 cm^–1 andC= 4·63B.The authors wish to express their thanks to the authorities of the Indian Institute of Science, Bangalore for kind permission to use their spectrophotometer. Two of the authors (B. C. V.Reddy and J. L.Rao) express their greatful thanks to the council of scientific and Industrial Research (New Delhi) for financial assistance.     

Optical absorption spectrum of chromium doped rubidium aluminium sulphate dodecahydrate

Optical absorption spectrum of chromium doped rubidium aluminium sulphate dodecahydrate single crystal is investigated. The electronic spectrum in the UV-VIS region is characteristic of Cr ³⁺ in trigonal symmetry and vibrational spectrum in the i.r. region is ascribed to the SO ₄²⁻ and H ₂O groups. The following crystal field parameters are evaluated for Cr ³⁺ in trigonal symmetry.Dq = 1840cm ⁻¹, Dσ = 140cm ⁻¹, Dτ = 140cm ⁻¹, B = 700cm ⁻¹ C = 3100cm ⁻¹.     

Absorption spectrum of VO2+ ion doped in caesium cadmium sulphate hexahydrate single crystal

Results of the optical absorption spectrum of VO²⁺ ion doped in caesium cadmium sulphate hexahydrate studied at room (300 K) and liquid nitrogen (77 K) temperatures are reported. The site symmetry of the ion is found to be C_4ν. Correlating the optical and ESR spectral data, the molecular orbital coefficients are evaluated.     

Optical absorption spectrum of Cr3+ ion doped in zinc cesium sulphate hexahydrate

Optical absorption spectrum of Cr³⁺ ion doped in zinc cesium sulphate hexahydrate single crystal has been studied both at room and liquid nitrogen temperatures. From the nature and position of the bands a successful interpretation of all the bands could be made assuming octahedral symmetry for the Cr³⁺ ion in the crystal. The observed bands are assigned to the transitions from the ground ⁴A_2g(F) state to the excited ²E_g(G), ²T_1g(G), ⁴T_2g(F) and ⁴T_1g(F) states.The crystal field parameters Dq = 1735 cm^?1, B = 635 cm^?1 and C = 4.75 B are found to give a good fit to the observed band positions.     

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     

Infrared absorption spectrum of the sodium uranyl acetate single crystal

The infrared absorption spectrum of the sodium uranyl acetate single crystal was studied experimentally at room temperature. The group-theoretical method is used to interpret the splitting of several bands in the spectrum into three components. The vibrations noted in the infrared spectrum are associated with types of symmetry.In conclusion, the authors thank Academician AS BSSR A. N. Sevchenko for his unflagging interest in the present investigation.     

EPR and optical absorption study of Cr doped diammonium hexaaqua magnesium sulphate single crystal

EPR measurements of Cr³⁺ doped diammonium hexaaqua magnesium sulphate single crystals are made at room temperature. The crystal field and spin Hamiltonian parameters are evaluated from the resonance lines obtained at different angular orientations. The value of g=1.9763±0.0002 and are evaluated. On the basis of EPR data the site symmetry of Cr³⁺ in the crystal is discussed. Optical absorption studies of single crystals are also carried out at room temperature. The orbital energies of the chromium ion are estimated from the optical absorption spectrum. The different bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed. The values of Racah parameters (B and C), crystal field parameter (Dq) and nephelauxetic parameters (h and k) are obtained as B=676,C=3371, , h=1.258 and k=0.21.     

Electronic absorption spectrum of Mn2+ ions doped in diglycine barium chloride monohydrate

The absorption spectrum of Mn²⁺ doped in diglycine barium chloride monohydrate has been studied at room temperature. The observed bands are assigned as transitions from the ${}^6\text{A}{}_{\mathrm{1g}}\text{(S)}$ ground state to various excited quartet levels of a Mn²⁺ ion in a cubic crystalline field. A new method has been suggested to evaluate the Racah parameters (B and C) accurately. The observed band positions are fitted with four parameters B, C, Dq and α, and the values obtained for the parameters are B= 810 cm^-1, C = 2990 cm^-1, Dq = 750 cm^-1 and α = 76 cm^-1.     

Optical absorption in tin monoselenide single crystal

Optical absorption in single crystals of tin monoselenide has been measured at room temperature with plane polarized light near the fundamental absorption edge. The electric field of the incident light was oriented parallel to the a- and b-crystallographic axes in the plane of cleavage. Results have been analyzed on basis of two- and three-dimensional models. Absorption near the fundamental edge was found to be due to indirect forbidden transition with two phonons involved in the process. The energy gap and phonon energies were found to be 0.948 eV and 54 and 21 meV for the a-axis and 0.902 eV and 41 and 20meV for the b-axis. The two-dimensional model gave results similar to those obtained from the three-dimensional model and could thus be used to describe the main optical properties of SnSe single crystal.     

Optical spectroscopy of Mn2+ ions in CaCl2 single crystals

Abstract

In the present investigation the excitation and fluorescence spectra and lifetimes of Mn²⁺ ions in calcium chloride, for various manganese concentrations and sample temperatures have been studied for the first time. The fluorescence spectrum consists of an asymmetric broad band, which upon lowering the sample temperature, shifts its maximum from 580 nm at 300 K to 596 nm at 11 K. This luminescence band was associated with the ⁴T_lg(⁴G)→⁶A_lg(⁶S) spin-forbidden transition in the manganese ions occupying Ca-sites in the lattice of CaCl₂. The excitation spectrum of the Mn²⁺ fluorescence revealed the features of manganese ions in octahedral coordination and consisted of nine excitation peaks which were associated with Mn²⁺-crystal-field-sensitive transitions. A crystal field analysis of the wavelength positions of these transitions by means of the model developed by Curie et al. allowed us to determine the magnitude of the cubic field splitting 10Dq, the reduced Racah parameter B', the Koide-Pryce covalency parameter ε and the spin transfer coefficients f _[sgrave] and f _σ. From the measurement of the temperature dependence of the Mn²⁺ fluorescence lifetime, we have also obtained information about the different mechanisms which are involved in the relaxation of excited Mn²⁺ ions in this host crystal in the temperature range (11–300 K).     

The photoacoustic absorption spectrum of VO2+ ions in cerium orthophoshate

The photoacoustic absorption spectrum of vanadium-doped CePO₄ samples has been observed at room temperature. Two absorption peaks are seen, one at 11200 cm^-1 and another at 14800 cm^-1. They are attributed to VO²⁺ ions in interstitial sites of distorted octahedral symmetry.     

Structural heterogeneities in the cubic ZnS crystal doped with Fe2+ ions

The structural state of the cubic Zn_0.999Fe_0.001S single crystal grown by the chemical transport method has been investigated using thermal neutron diffraction at 300 K for the first time. It has been found that the diffraction patterns of the crystal contain diffuse scattering regions with wave vectors q = 0 and $q = (\bar 1/3, 1/3 , 0)2\pi /a$ . The experimental results have been discussed in the context of the available information on neutron diffraction in the Zn_0.999Fe_0.001Se compound. It has been shown that the effects of diffuse scattering are caused by local shear deformations of the metastable cubic lattice of the compound under investigation.     

Optical properties of Dy ions in sodium gadolinium tungstates crystal

Dy³⁺-doped NaGd(WO₄)₂ crystal with sizes of about Φ20×40 mm² was grown by the Czochralski technique along the (0 0 1) orientation. Polarized absorption spectra, fluorescence spectra, and fluorescence decay curve of Dy³⁺-doped NaGd(WO₄)₂ have been recorded at room temperature. Based on the Judd-Ofelt (J-O) theory, the intensity parameters from the measured line strengths were evaluated. The J-O parameters were used to predict radiative transition probabilities, radiative lifetimes and branching ratios for various excited levels of Dy³⁺-doped NaGd(WO₄)₂ crystal. The luminescent quantum efficiency of the ⁴F_9/2 level was determined to be approximately 63% for this material. The emission cross-section of the ⁴F_9/2→⁶H_13/2 transition was estimated by using the Füchtbauer-Ladengurg method.     

Vibronic transitions in the absorption spectrum of a U3+-doped elpasolite single crystal

Conclusions We have presented the absorption bands associated with f−f and f−d transitions. The investigated ion was placed in the center of symmetry. For that reason pure electric dipole f−f transitions are forbidden, but thet are allowed for f−d transitions. Nevertheless, pronounced vibronic transitions were obseved not only in the f−f lines but also for f−d bands. An assignment of the observed lines supported by previously reported Raman and IR spectra is proposed. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 4, pp. 58–62, July–August, 1995.     

Investigating the impurity structure for Fe3+ ions doped into rutile titanium dioxide single crystal

The local environment around Fe³⁺ centers in rutile TiO₂ crystals is studied by employing fourth-order perturbation theory formula based on the dominant spin–orbit coupling mechanism. The zero-field splitting parameters (ZFSPs) D and E and crystal field parameters are modeled for the Fe³⁺ ions not only at the substitution Ti⁴⁺ site, but also at the interstitial site with local symmetry D_2h. In order to acquire the best agreement between the calculated ZFSPs and those measured by electron magnetic resonance, the model parameters are adjusted on the basis of several approaches. This enables us to determine the feasible values of the structural distortions resulting from dopant Fe³⁺ ions. Consequently, it is confirmed that Fe³⁺ ions substitute for Ti⁴⁺ sites in rutile TiO₂ crystals.     

Absorption spectrum of Mn2+ ions doped in diammonium hexaaquamagnesium(II) sulfate

Optical absorption is a tool to investigate the site symmetry of metal ion and associated distortion in doped single crystals. It provides the energy of different orbital levels of metal ion and separation among them. Mn²⁺ ions in various single crystals and glasses have been the subject of recent investigations [1–3]. We have studied optical absorption spectra of Mn²⁺ doped diammonium hexaaquamagnesium(II) sulfate in order to obtain the energy level ordering using matrices of Tanabe and Sugano [4] and to discuss the associated distortion.     

Optical absorption spectrum of Cr3+ in natural ruby

Two sharp line-like bands calledN andR lines on the red side, a close doublet (B lines) on the violet side and two broad bands are observed for natural ruby. At liquid air temperature the splitting ofR line was found and also three sharp-bands calledR, R′ andB lines are identified with spin-forbidden transitions of² E,² T ₁ and² T ₂. The two broad bands calledU band andY band are assigned accordingly to the spin-allowed transitions⁴ T ₂ and⁴ T ₁ respectively. The observed bands of natural ruby have been attributed to Cr³⁺ ion in an octahedral environment with trigonal distortion. The crystal field parameters which gave a good fit to the observed band positions areB=732 cm⁻¹,C=4.25B,Dq=1830 cm⁻¹,V=−1996 cm⁻¹ andλ=34 cm⁻¹.