Theoretical explanation of electron paramagnetic resonance and optical parameters for Cu<Superscript>2+</Superscript> ion in LiNbO<Subscript>3</Subscript> crystal

The EPR parameters, anisotropic g-factors g _x , g _y and g _z for cu²⁺ ion and hyperfine structure constants A _x , A _y and A _z for Cu²⁺ in LiNbO₃ crystal are calculated by the method of diagonalizing the full Hamiltonian matrix. The crystal-field parameters contact with the crystal structure by the aid of the superposition model. The optical transition parameters are calculated using Zhao crystal-field model. The calculated results are in good agreement with the observed values. The results are discussed.      

The Interaction Between Levofloxacine Hydrochloride and DNA Mediated by Cu2+

Levofloxacin (LEV) is a fluoroquinolone antimicrobial agent. LEV also inhibits DNA synthesis and is bactericidal. The mechanisms of the interaction among LEV, DNA and Cu2+ are studied by fluorescence method. In the paper, the results show that LEV and Cu2+ can form binary complex, and also LEV and DNA can form complex mediated by Cu2+. The composition of the complex is determined. The affects to the reaction are also found.     

Effect of isoelectronic impurities K<Superscript>+</Superscript> and I<Superscript>−</Superscript> on luminescence of CsBr:Eu<Superscript>2+</Superscript> crystals

We have investigated the photoluminescence (PL) and photostimulated luminescence (PSL) spectra at 300 K to study the effect of isoelectronic impurities K⁺ and I⁻ on the formation and energy structure of Eu²⁺-V_Cs isolated dipole centers and aggregate centers in the form of single crystals of CsEuBr₃ in CsBr:Eu²⁺ single crystals. We have shown that K⁺ and I⁻ impurities in a concentration of 5 mol% do not have a substantial effect on the energy spectrum of isolated dipole centers in CsBr:Eu²⁺ single crystals and the processes for the formation of such centers during growth of CsBr:Eu single crystals from the melt by the Bridgman method. We have established that in Cs_0.95K^0.05Br:Eu²⁺, more favorable conditions are realized for the formation of aggregate centers than in CsBr:Eu²⁺ and CsBr^0.95K^0.05Br:Eu²⁺ single crystals. So in order to improve the storage properties of phosphors based on CsBr:Eu²⁺, in particular for increasing the efficiency of PSL excitation, it is expedient to dope them with K⁺ impurity in a concentration up to 5 mol%. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 627–630, September–October, 2007.     

Up-conversion emissions of Er<Superscript>3+</Superscript>-Yb<Superscript>3+</Superscript> codoped Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles by the arc discharge synthesis method

The Er³⁺-Yb³⁺ codoped Al₂O₃ nanoparticles with an average particle size of about 50 nm have been synthesized by an arc discharge synthesis method. The green and red up-conversion emissions centered at about 526, 547 and 677 nm, corresponding respectively to the ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions of Er³⁺, were detected by a 978-nm semiconductor laser diode excitation. The Annealing has evident effect on the up-conversion emissions of the samples: The red up-conversion emission is noticeable before annealing; however, the green up-conversion emission becomes predominant after annealing. The mixture of (Er,Yb)₃Al₅O₁₂ and α-(Al,Er,Yb)₂O₃ phases is more favorable for green up-conversion emissions due to an enhancement of the ESA (I) of ⁴I_11/2+a photon→⁴F_7/2 and ET (III) of ²F_5/2(Yb³⁺)+⁴I_11/2(Er³⁺)→²F_7/2(Yb³⁺)+⁴F_7/2(Er³⁺) processes. The two-photon absorption up-conversion process is involved in the green and red up-conversion emissions. The results have proved that arc discharge synthesis is a new promising preparation technology for optical materials. Supported by National Natural Science Foundation of China (Grant No. 10804015), the Scientific Research Foundation for Doctor of Liaoning Province (Grant No. 20071095), and the Educational Committee Foundation of Liaoning Province (Grant No. 2008123)     

Wavelength tunable linear cavity cladding pump Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript>co-doped fiber laser operating in L-band

We have demonstrated a novel tunable linear cavity Er³⁺/Yb³⁺ co-doped fiber laser, which utilizes amplified spontaneous emission as a secondary pump source so that it can operate in L-band. The tuning wavelength range can be up to 34 nm, from 1588.6 to 1622.6 nm, and the output power excursion of the laser at different wavelengths can be less than 0.4 dB by using a two sections of high-birefringence fiber loop mirror as the wavelength filter. The high output power of 200 mW is realized by using the cladding-pump.     

A Novel Hg<Superscript>2+</Superscript> Selective Ratiometric Fluorescent Chemodosimeter Based on an Intramolecular FRET Mechanism

A irreversible Hg²⁺ selective ratiometric fluorescence probe FR, a fluorescein fluorophore linked to a rhodamine B hydrazide by a thiourea spacer, was designed and synthesized. The developed probe FR exhibited great ratiometric fluorescence enhancement and remarkable yellow-magenta color change toward Hg²⁺ with excellent selectivity in aqueous acetone solution, and the ratiometric fluorescence response to Hg²⁺ was not interfered by other metal cations including Fe³⁺, Co²⁺, Ni²⁺, Cr³⁺, Zn²⁺, Pb²⁺, Cd²⁺, Ca²⁺, Mg²⁺, Ba²⁺ and Mn²⁺. The linear range and the detection limit of this supposed ratiometric fluorescence method for Hg²⁺ were 0.0–10.0 × 10⁻⁶ and 5 × 10⁻⁸ M, respectively.     

Synthesis and characterization of Mn<Superscript>2+</Superscript>-doped ZnS nanoparticles

Mn²⁺-doped ZnS nanoparticles were prepared by chemical arrested precipitation method. The samples were heated at 300, 500, 700 and 900°C. The average particle size was determined from the X-ray line broadening. Samples were characterized by XRD, FTIR and UV. The composition was verified by EDAX spectrum. The hexagonal structure of the sample was identified. The size of the particles increased as the annealing temperature was increased. The crystallite size varied from 5 nm to 34 nm as the calcination temperature increased. At around 700°C, ZnS is converted into ZnO phase due to oxidation. The emission peak of the sample is observed at 300 nm resulting in blue emission. The solid state theory based on the delocalized electron and hole within the confined volume can explain the blue-shifted optical absorption spectra. UV-VIS spectro-photometric measurement shows an indirect allowed band gap of 3.65 eV.      

Quantum cutting in Gd<Subscript>2</Subscript>SiO<Subscript>5</Subscript>: Eu<Superscript>3+</Superscript> by VUV excitation

The emission and excitation spectra of Gd₂SiO₅∶Eu³⁺ were investigated using the VUV beam line of the Beijing Synchrotron Radiation Facility (BSRF). The experimental results were discussed in the frame of visible quantum cutting process involved in Gd³⁺−Eu³⁺ system. Upon direct excitation into the⁶G _J states of Gd³⁺, two visible photon emissions from Eu³⁺ were observed. Cursory evaluation proved that Gd₂SiO₅∶Eu³⁺ is an efficient visible quantum cutter.     

Spectral Investigations on Cu<Superscript>2+</Superscript>-Doped ZnO Nanopowders

Cu²⁺-doped ZnO nanopowders, synthesized at room temperature by mild and simple solution method, are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), optical, electron paramagnetic resonance (EPR) and Fourier-transform infrared (FT-IR) techniques. From XRD and SEM, the crystal structure is identified as hexagonal, and the average crystallite size is around 53 nm. Lattice cell parameters are evaluated. The optical and EPR spectral investigations suggest that the Cu²⁺ ion enters the host lattice in two tetragonally distorted octahedral sites. Crystal field, tetragonal field, spin Hamiltonian and bonding parameters are estimated.     

Wavelength and oscillator strength of dipole transition 1s<Superscript>2</Superscript>2p—1s<Superscript>2</Superscript><Emphasis Type="Italic">n</Emphasis>d for Mn<Superscript>22+</Superscript> ion

The transition energies, wavelengths and dipole oscillator strengths of 1s²2p—1s² nd (3⩽n⩽9) for Mn²²⁺ ion are calculated. The fine structure splittings of 1s² nd (n</9) states for this ion are also evaluated. In calculating energy, the higher-order relativistic contribution is estimated under a hydrogenic approximation. The quantum defect of Rydberg series 1s² nd is determined according to the quantum defect theory. The results obtained in this paper excellently agree with the experimental data available in literatures. Supported by the National Natural Science Foundation of China (Grant No. 10774063)     

VUV luminescence of Er<Superscript>3+</Superscript> ions in LiYF<Subscript>4</Subscript> and BaY<Subscript>2</Subscript>F<Subscript>8</Subscript> crystals

Vacuum ultraviolet luminescence of Er³⁺ ions in LiYF4 and BaY₂F₈ crystals has been investigated. It is revealed that under excitation by 193 nm radiation from an ArF excimer laser the interconfigurational 5d–4f radiative transitions in Er³⁺ ions are observed. It is shown that from the LiYF₄:Er crystal only the spin-forbidden luminescence (λ = 165 nm) is detected, whereas both the spin-forbidden (λ = 169 nm) and spin-allowed (λ = 160.5 nm) components are observed from the BaY₂F₈:Er crystal.     

Tunable optical parametric oscillator based on a KTP crystal,pumped by a pulsed Ti<Superscript>3+</Superscript>:Al<Subscript>2</Subscript>O<Subscript>3</Subscript> laser

We present the characteristics of an optical parametric oscillator based on a KTP crystal, pumped with noncritical phase matching by a pulsed Ti³⁺:Al₂O₃ laser, tunable in the range 677–970 nm. Tunable generation of signal and idler waves is obtained in the ranges 1030–1390 nm and 2690–3050 nm respectively. The efficiency of conversion of the pump to the signal wave is ≈23%, which for pulses of duration ≈8 nsec ensures an energy in the range 1.0–11.5 mJ. The width of the emission spectrum for the signal wave is within the range 0.8–1.8 nm and is predominantly determined by the linewidth of the Ti³⁺:Al₂O₃ pump laser. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 3, pp. 351–356, May–June, 2007.     

Zero-field splitting of <Superscript>4</Superscript><Emphasis Type="Italic">T</Emphasis><Subscript>2</Subscript> term for 3d<Superscript>3</Superscript> ions in tetragonal symmetry

By taking into account slight interactions, i.e. spin-spin, spin-other-orbit and orbit-orbit interactions, in addition to spin-orbit interaction, the zero-field splitting of ⁴ T ₂ state for 3d³ ions at tetragonal symmetry has been studied. The convergence of the approximation perturbation formula of ⁴ T ₂ state for 3d³ ions at tetragonal symmetry has been investigated, and the contributions to zero-field splitting arising from magnetic interaction and tetragonal crystal field are discussed. It is found that there exists combined mechanism between magnetic interactions and tetragonal crystal field.      

Study of structural phase transitions in YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>6+δ</Subscript> by x-ray photoelectron spectroscopy

We have used x-ray photoelectron spectroscopy to investigate the charge state of oxygen found in the basal structural plane of YBa₂Cu₃O₆+γ.. We have observed a change in this state after thermal treatment, with a transition to the adjacent structural phase region. We have shown that changes in the charge state of oxygen can be used as an indicator of structural changes occurring in YBa₂Cu₃O₆+δ.. We have found that the rate of structural relaxation yttrium barium cuprate depends on the amount of structural water it contains. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 195–198, March–April, 2007.     

Passive Q-switching of a laser-diode-pumped intracavity-frequency-doubling Nd:Nd<Superscript>3+</Superscript>:NaY(WO<Subscript>4</Subscript>)<Subscript>2</Subscript>/KTP laser with Cr<Superscript>4+</Superscript>:YAG saturable absorber

Nd³⁺:NaY(WO₄)₂, known as Nd:NYW, is a new type crystal. By using laser-diode as pump source, a passive Q-switching of intracavity-frequency-doubling Nd:NYW/KTP laser has been realized with Cr⁴⁺:YAG saturable absorber. The dependence of pulse repetition rate, pulse energy, pulse width, and peak power on incident pump power for different small-signal transmissions of Cr⁴⁺:YAG are measured. The coupled rate equations are used to simulate the Q-switched process of laser, and the numerical solutions agree with the experimental results.     

Theory studies of the local lattice distortions and the EPR parameters for Cu2+, Mn2+ and Fe3+ centres in ZnWO4

The local lattice distortions and the electron paramagnetic resonance (EPR) parameters (g factors, hyperfine structure constants and zero-field splittings) for Cu²⁺, Mn²⁺ and Fe³⁺ in ZnWO₄ are theoretically studied based on the perturbation calculations for rhombically elongated octahedral 3d⁹ and 3d⁵ complexes. The impurity centres on Zn²⁺ sites undergo the local elongations of 0.01, 0.002 and 0.013 Å along the C₂ axis and the planar bond angle variations of 8.1°, 8.0° and 8.6° for Cu²⁺, Mn²⁺ and Fe³⁺, respectively, due to the Jahn–Teller effect and size and charge mismatch. In contrast to the host Zn²⁺ site with obvious axial elongation (～0.31 Å) and perpendicular (angular) rhombic distortion, all the impurity centres demonstrate more regular octahedral due to the above local lattice distortions. The copper centre exhibits significant Jahn–Teller reductions for the spin-orbit coupling and orbital angular momentum interactions, characterised by the Jahn–Teller reduction factor J (≈0.29 ? 1). The calculated EPR parameters agree well with the experimental results. The local structures of the impurity centres are analysed in view of the corresponding lattice distortions.     

M<Superscript>2</Superscript> of MOPA CuBr Laser Radiation

The beam propagation factor, M² of the master-oscillator power-amplifier (MOPA) CuBr laser emission compliant with ISO 11146 is studied methodically. Statistical parameters of 2D intensity profile of the near and far fields of MOPA laser radiation are measured by a beam analyzing technique as functions of timing delay between MO and PA. For first time the influence of the gas buffer (causing the radiation profile to change from annular to top-hat and Gaussian-like) and light polarization on CuBr laser beam focusability (M²) was under investigation. The MOPA gain curve is found and the influence of gain on the input signal (from MO into PA) due to the absorption/amplification in PA on the field profiles is shown. For annular radiation M² range is from 13–14 (small delays) to 5–6 (large delays) and for filled-center radiation M² is 6–7 (small delays) and at the end of gain curve is as much as 4. With polarized light, M² drops to 3 at the end of gain curve. The brightness of laser emission with hydrogen goes up 3–5 times and the linearly-polarized beam is at least 40% brighter than that of partial or non-polarized beams.     

Physical and Spectral Investigations of Cu<Superscript>2+</Superscript>-Doped Alkali Zinc Borate Glasses

Physical and spectral studies on 20ZnO + xLi₂O + (30-x)Na₂O + 50B₂O₃ (5 ≤ x ≥ 25) doped with 0.1 mol% of paramagnetic CuO impurity are carried out. Powder X-ray diffraction patterns of the glass samples confirm the amorphous nature. The physical parameters of all the glasses were also evaluated with respect to the composition. The electron paramagnetic resonance spectra of all these glasses exhibit resonance signals that are characteristic of Cu²⁺ ions. The optical absorption spectra also confirm the Cu²⁺ ion in tetragonally elongated octahedral site. Various crystal field, spin-Hamiltonian and bonding parameters are evaluated. It is observed that the mixed alkali effect is significant.     

Electron paramagnetic resonance parameters of Mn<Superscript>4+</Superscript> ion in h-BaTiO<Subscript>3</Subscript> crystal from a two-mechanism model

The EPR parameters (g factors g _‖, g _⊥ and zero-field splitting D) of Mn⁴⁺ ion in h-BaTiO₃ crystal are calculated from the complete high-order perturbation formulas based on a two-mechanism model for the EPR parameters of 3d ³ ions in trigonal symmetry. In the model, not only the widely used crystal-field mechanism, but also the charge-transfer mechanism (which is not considered in crystal-field theory) are included. The calculated results are in reasonable agreement with the experimental values. The relative importance of charge-transfer mechanism to EPR parameters and the defect structure of Mn⁴⁺ centre in h-BaTiO₃ crystal obtained from the calculations are discussed.      

Instabilities of the Conventional Nucleus-Nucleus Interactions for (<Superscript>3</Superscript>H<Superscript>4</Superscript>He) Proton Pickup Cross-Sections

The angular distributions of the ²⁶Mg, ²⁸Si, ³⁰Si(³H, ⁴He) reactions have been analyzed using the exact finite-range DWBA calculations. The optical model potential is assumed to have the conventional spin-orbit potential. The obtained cross-sections with the spin-orbit potential are not significantly different from those calculated using the phenomenological Woods–Saxon form factors in the forward angle regions. The inclusion of the spin-orbit potential gives the best fit to the data and greatly improves the large angle cross-sections. Different reasonable spectroscopic factors are found to account well for the cross-section magnitudes.