Optical absorption spectrum of Ni2+ ions doped in sodium potassium sulphate single crystal

Single crystals of nickel-doped sodium 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 observed bands could be made assuming the octahedral symmetry for the Ni^{2 +} ion in the crystal. The bands have been ascribed to 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 experimental and calculated energies are in good agreement. The crystal field parameters derived areDq= =880 cm^–1,B= 900cm^–1 andC=3600 cm^–1.One of the authors, Sujatha John expresses her thanks to the Secretary and the Principal, R. B. V. R. Reddy College, Hyderabad for according her permission to pursue the M. Phil. course.     

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.     

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     

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.     

Electronic spectrum of Cu2+ in rubidium magnesium sulphate hexahydrate

The single crystal electronic spectrum of Cu²⁺ in rubidium magnesium sulphate hexahydrate is interpreted in terms of the crystal field ofD _2h symmetry. From the EPR spectrum of the polycrystalline sample theg andA-values and hence the bonding parameter ( ²) are evaluated. Orbital reduction parameters are calculated by correlating the optical and EPR data.The authors wish to express their thanks to Prof. S. V. J. Lakshman for his interest in the work, and to UGC (India) for financial assistance.     

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.     

Phase transition in potassium lithium sulphate

Phase transition and lattice parameter variation with temperature of potassium lithium sulphate have been studied. Precision lattice parameters have been determined at various temperatures, ranging 30°C to 400°C. The diffraction pattern obtained above 435°C differs from that taken at room temperature suggesting a structural change, contrary to the reports of Fischmeister and others. Presented at the Symposium on Crystallography and Crystal Physics, Osmania University, Hyderabad, December 1977.     

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.     

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.     

Electronic absorption spectrum of Cr3+ in calcium formate single crystals

Optical absorption spectra of Cr³⁺ ions in calcium formate single crystals with two different dopants have been studied at room and liquid nitrogen temperatures. The observed spectra have been attributed to Cr³⁺ ions in octahedral environment with tetragonal distortion. The values of the crystal field and Racah parameters have been evaluated.     

Electronic absorption spectrum of CO+ in an ion beam

The He+He⁺¹ interactions have been studied, as a function of the internuclear separation R, in terms of the electronic forces acting on the nuclei and the change in the charge distribution. The analysis reveals that at large R the atomic densities are polarized inwards, causing an attractive force on each nucleus, while at small R the difference in the nature of the interactions in the ²Σ_u and ²Σ_g systems is noted. It is seen that the He+He⁺¹ (²Σ_u) interaction is less attractive than the He⁺¹+He⁺¹ interaction at lower values of R.     

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.     

Temperature dependent study of the single crystal electronic spectrum of octahedral Ni2+ ion subjected to distortions in weak fields

Electronic spectra of two high spind ⁸ nickel complexes, Ni(en)₃Cl₂.2H₂O and Ni(OAc)₂.4H₂O, are reported. Polarized spectra were measured at 298 K. Temperature dependent spectra were measured using unpolarized light down to 20 K. The spectra at 20 K are well resolved revealing the features of spin-forbidden transitions and vibrational fine structure on some of the bands. Some of the spectra are deconvoluted to separate out the overlapping bands. The assignments are made usingD ₃ symmetry for Ni(en)₃Cl₂.2H₂O complex whileD ₄ symmetry is used for Ni(OAc)₂.4H₂O. The energies of the spectroscopic states are calculated and compared with the observed transition energies. The distortion parameters are determined.     

Electron spin resonance and optical absorption studies on copper-doped lithium hydrazinium sulphate single crystals

ESR and optical absorption studies have been carried out on Cu²⁺-doped lithium hydrazinium sulphate single crystals at 303 K. The spin-Hamiltonian parameters evaluated indicate a N₂O₂ square planar environment for Cu²⁺ ion in this lattice. The correlation ofESR and crystal structure data leads us to conclude that Cu²⁺ ion enters the lattice interstitially. Charge compensation is achieved by the release of protons. Using the optical absorption andESR data, bonding parameters and orbital reduction factors are also evaluated.     

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.     

EPR and optical absorption studies of vanadyl impurity in lithium hydrogen oxalate single crystal

Electron paramagnetic resonance (EPR) and optical absorption studies of vanadyl ions in lithium hydrogen oxalate monohydrate single crystal and powder are reported at room temperature. Single crystal rotations in each of the three mutually orthogonal crystalline planes, $a{b}^1$, $b^1{c}^1$ and $a{c}^1$ indicate four different vanadyl complexes. The detailed investigation of EPR spectra indicates that one of the VO^{2 +} sites (the intense one) may enter the lattice substitutionally and the other three occupy the interstitial positions. From the angular variation, the spin Hamiltonian parameters are evaluated and discussed. The optical absorption spectrum shows four bands. From the optical and EPR data, various bonding parameters are determined and the nature of bonding in the crystal is discussed.     

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.     

EPR and optical absorption studies of vanadyl impurity in zinc potassium phosphate hexahydrate single crystal

Electron paramagnetic resonance (EPR) study of VO²⁺ doped zinc potassium phosphate hexahydrate single crystal is carried out. The angular variation of the spectra is studied in the three crystallographic planes. The principal value of spin Hamiltonian parameters g and A and the direction cosines which principal axes make with the crystallographic axes are determined. The observed values are site I: g_∥=1.9664±0.0002, g_⊥=1.9973±0.0002, A_∥=150±2×10⁻⁴, A_⊥=60±2×10⁻⁴ cm⁻¹; site II: g_∥=1.9276±0.0002, g_⊥=1.9921±0.0002, A_∥=155±2×10⁻⁴ and A_⊥=62±2×10⁻⁴ cm⁻¹. By comparison of direction cosines of g from EPR with the direction cosines of different bonds obtained from crystal structure data it is ascertained that the VO²⁺ ion occupies Zn²⁺ substitutional sites. The optical absorption study of the crystal at room temperature is also carried out. The bands observed in the optical absorption spectrum are attributed to d-d transitions. The EPR results together with the optical data are employed to estimate the molecular orbital (MO) coefficients. These MO coefficients (also called bonding coefficients) are further used to discuss the nature of bonding of VO²⁺ ion with different ligands in the crystal.     

Superconductivity and single crystal growth of Ni0.05TaS2

Superconductivity was discovered in a Ni_0.05TaS₂ single crystal. A Ni_0.05TaS₂ single crystal was successfully grown via the NaCl/KCl flux method. The obtained lattice constant $c$ of Ni_0.05TaS₂ is 1.1999 nm, which is significantly smaller than that of 2H–TaS₂ (1.208 nm). Electrical resistivity and magnetization measurements reveal that the superconductivity transition temperature of Ni_0.05TaS₂ is enhanced from 0.8 K (2H–TaS₂) to 3.9 K. The charge-density-wave transition of the matrix compound 2H–TaS₂ is suppressed in Ni_0.05TaS₂. The success of Ni_0.05TaS₂ single crystal growth via a NaCl/KCl flux demonstrates that NaCl/KCl flux method will be a feasible method for single crystal growth of the layered transition metal dichalcogenides.