Electronic spectrum of cobalt doped rubidium zinc sulphate hexahydrate

Optical absorption spectrum of Co²⁺ doped rubidium zinc sulphate hexahydrate has been investigated both at room and at liquid nitrogen temperatures. The gross features of the observed spectrum are characteristic of octahedral symmetry associated with spin-orbit interaction. The interelectronic repulsion (B, C), crystal field (Dq) and spin-orbit () parameters which give a good fit to the observed band positions areB = 860 cm^–1,C = 3870 cm^–,Dq = 980 cm^–1,= 500 cm^–1. The non-ligand bands observed in the spectrum are attributed to vibrational modes of water molecule.The authors are thankful to the Council of Scientific and Industrial Research, New Delhi (India) for financial support.     

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+ 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 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.     

Optical absorption and reflectivity spectra of highly chromium doped CdTe alloy and layer

In the present work, a CdTe alloy doped with a relatively high concentration of chromium (1%), and a CdTe:Cr layer, have been studied. Absorption and reflectivity spectra were measured at room temperature. They indicate the presence of chromium in the divalent state, both in the alloy and in the layer.      

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 and nuclear magnetic resonance in lithium titanium spinel doped by chromium

The optical absorption and nuclear magnetic resonance spectra of Li_{4 − x} Cr_3x Ti_{5 − 2x} O₁₂ (x = 0, 0.01, 0.02, 0.04) solid solutions have been investigated. It has been found that, in the Li₄Ti₅O₁₂ spinel, lithium ions migrate from tetrahedral to octahedral positions with increasing temperature. Doping of chromium to the spinel favors an increase in the fraction of tetrahedrally coordinated lithium and hinders diffusion.     

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.     

Optical study of praseodymium doped yttrium aluminium garnet

The absorption and fluorescence spectra of YAG crystals doped with praseodymium at 1% level are investigated through dye laser spectroscopy. The spectra can be interpreted as evidence for at least three series of crystallographic sites for Pr³⁺, but only the transitions which involve the ground state are really complex, that is multi-sites like. It is suggested that an electronphonon interaction occurs through resonance with peaks in the density of phonon states and ground state Stark levels in the range 350–750 cm^–1. This creates new vibronic states and the appearance of a large number of lines for transitions involving ground state especially if laser excitation of the fluorescence is used.Presented at the International Symposium on Solid State Chemistry, October 28–31, 1986, Karlovy Vary, Czechoslovakia.     

Optical emission spectrum of rubidium atoms isolated in solid krypton

Saturation induced minima of the output power of a He/Ne-laser appear if Zeeman splitting equals the frequency separation. These minima have been investigated as a function of pressure. The results show pressure broadening caused by velocity changing and alignment destroying collisions. In contrast to Lamb-dip measurements the effect of phase changing collisions on collision broadening is negligible.     

Optical and electrical characterization of aluminium doped ZnO layers

Al doped ZnO (ZAO) thin films (with Al-doping levels 2 at.%) were deposited at different deposition parameters on silicon substrate by reactive magnetron sputtering for solar cell contacts, and samples were investigated by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS) and spectroscopic ellipsometry (SE). Specific resistances were measured by the well known 4-pin method. Well visible columnar structure and in most cases voided other regions were observed at the grain boundaries by TEM. EELS measurements were carried out to characterize the grain boundaries, and the results show spacing voids between columnar grains at samples with high specific resistance, while no spacing voids were observed at highly conductive samples. SE measurements were evaluated by using the analytical expression suggested by Yoshikawa and Adachi [H. Yoshikawa, S. Adachi, Japanese Journal of Applied Physics 36 (1997) 6237], and the results show correlation between specific resistance and band gap energy and direct exciton strength parameter.     

Optical absorption studies on cobalt doped struvite

Abstract

Optical absorption spectrum of cobalt doped MgNH₄PO₄ · 6H₂O (struvite) is investigated in UV-VIS-NIR regions. The spectrum in UV-VIS-NIR region is attributed to Co²⁺ in octahedral symmetry whereas the IR spectrum is attributed to vibrations due to PO₄ ^3-, NH₄ ⁺ and H₂O. The following crystal field (Dq) and interelectronic repulsion (B, C) parameters are evaluated: Dq = 940cm^?1, B = 870cm^?1 and C = 3970cm^?1.     

Electron spectrum and intrinsic absorption of heavily doped n-GaAs

The article presents results of a numerical calculation, made with a computer, of several parameters and functions characterizing the electron spectrum of heavily doped semiconductors; in addition, the article presents theoretically calculated and experimentally obtained dispersion curves of the absorption coefficient in the region of interband transitions in heavily doped n-GaAs. The numerical calculation method is based upon the work of V. L. Bonch-Bruevich, who used Green functions. Calculations and experimental measurements were made for n-GaAs with free electron concentrations of 4.8·10¹⁸ cm^?3 at temperatures of 10–610?K. Agreement between the theoretically calculated and the experimentally obtained values of the absorption coefficient is observed in the edge region at photon energies exceeding the width of the forbidden band of the pure semiconductor.     

光频链接的双光梳气体吸收光谱测量

双光梳光谱技术以其无运动部件快速采样、高分辨率探测等优势成为宽带激光光谱测量中的热点技术.但受限于常用微波锁定双光梳光源间的噪声特性,双光梳光谱技术仍难以发挥其探测潜能.本文报道一种光频域互相链接的双光梳光谱探测方案.通过将两台激光器的偏置频率同时锁定到一个窄线宽激光器上,既免去了结构复杂且成本高昂的非线性自参考系统,又将双光梳间的共同参考点设置到了光频范围,抑制了双光梳光谱采样抖动,实现光谱探测性能的提升.~(13)C_2H_2的ν_1+ν_3 P支光谱数据测量数据分析结果表明:谱线位置与文献结果符合良好,光谱分辨率为0.086 cm~(-1),信噪比200:1(62.5 ms,100幅平均),相应的秒均噪声等效吸收系数达6.0×10~(-6)cm~(-1)·Hz~(-1/2).该工作为双光梳光谱测量的实际应用提供了一种高精度、低成本、易于实现的解决方案.     

Optical,dielectric and ferroelectric behaviour on doped lithium sulphate crystals

Optically transparent single crystals of urea doped with lithium sulphate (ULS), thiourea doped with lithium sulphate (TLS) and cupric chloride doped with lithium sulphate (CuLS) were grown in aqueous solution by slow evaporation technique at room temperature. Single crystal X-ray diffraction analysis confirmed the changes in the lattice parameters of the ULS, TLS and CuLS. The lattice parameters and the quality of doped crystals were confirmed by powder X-ray diffraction studies. The functional groups present in the ULS, TLS and CuLS crystals were determined qualitatively by using Fourier transform infrared (FTIR) spectroscopy. Optical absorption studies revealed that doped crystals acquire very low absorption in the entire visible region. The energy dispersive X-ray analysis (EDAX) gives the chemical composition of the grown crystal. CHN analysis confirmed the presence of carbon, hydrogen and nitrogen in the added dopants. The dielectric constant and dielectric loss of the doped crystal were studied as a function of frequency and temperature and the ferroelectric property of the crystal was confirmed by dielectric studies.     

Optical absorption edge in doped and undoped ZnSe crystals

The optical absorption near the fundamental edge has been investigated for different types of doped and undoped cubic ZnSe crystals. Crystals grown from the vapour phase, with and without doping, and crystals grown by the chemical transport technique are compared.Results of absorption coefficient measurements made from 77 to 313 LK are discussed and it is shown that for undoped samples, the absorption tail is dominated by electrons-phonons interactions and Urbach's rule is nearly verified, whereas for doped samples the influence of defects is preponderant.     

Optical absorption,thermoluminescence (TL) glow and emission studies on rubidium chloride

Single crystals of suprapure RbCl after irradiation and subsequent F-light bleaching show an absorption band on the low energy side of F-band and enhancement of F-excited states, suggesting the formation of F_A(K) centres (in the “Suprapure” labelled material about 100 ppm of potassium is present). TL of such irradiated samples show four glow peaks. Upon F-light bleaching a new glow peak appears on the low temperature side. The glow peaks corresponding to F_A(K) centres have been identified. The spectral distribution of TL emission under different glow peaks has been studied. It is found that all the glow peaks have broad emission bands around 1.5, 2.5 and 2.8 eV. However, the high temperature peak shows additional emission around 2.1 and 3.9 eV. An attempt is made to interpret these emission bands in terms of recombination processes involving F and V type centres in these irradiated crystals. A tentative energy level diagram indicating various TL processes is also suggested.     

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 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.