Multireference CI calculations of radiative transition probabilities between low lying quartet states of the C2+ ion

Potential energy functions for the ten lowest electronic states of the C₂⁺ ion have been calculated from correlated CASSCF and MC-CI electronic wavefunctions and used for derivation of the spectroscopic constants. The predicted values are expected to be accurate within 0.01 Å for R_e, 20–30 cm⁻¹ for ω_e and 0.05–0.1 eV for T_e. For the three lowest quartet states the electronic transition moment functions have also been calculated. For the transitions among these states, radiative lifetimes and absorption oscillator strengths are given which should be accurate within about 15%.     

QUANTUM EFFICIENCY AND MULTIPHONON NONRADIATIVE TRANSITION OF Er3+ IONS IN FLUORIDE GLASS

Optical absorption, emission and excitation spectra, lifetimes of ⁴S_3/2 state and ⁴F_9/2 state from 10K to 500K, and Raman spectra were measured for Er³⁺ ions in fluoride glass. The radiative transition probabilities were calculated on the basis of Judd-Ofelt theory. The nonradiative transition probabilities and the quantum efficiencies were determined by calculating the difference between the measured lifetimes and the calculated radiative transition probabilities. The temperature dependence of nonradiative transition provavility was investigated using the Huang-Rhys theory of multiphonon relaxation , in which two kinds of phonons as well as the parameter s were taken into consideration. A fairly good agreement of the theoretical calculation with the experimental results has been obtained. The value of s is estimated and the effect of s is discussed.     

Spectroscopic analysis of Pr3+:CaYAlO4 crystal

The polarized absorption, emission spectra and decay time measurements of Pr³⁺-doped CaYAlO₄ single crystal have been performed at room temperature. Based on the Judd–Ofelt theory, the spectroscopic parameters \(\Upomega_{t} (t = 2,4,6)\) , radiative transition probabilities, radiative lifetimes and branching ratios were obtained. The stimulated emission cross-section, fluorescence lifetimes and the quantum efficiency of the promising laser transition were also calculated and compared with other reported crystals. The results show that Pr³⁺:CaYAlO₄ is a promising candidate for visible solid-state laser emission.     

Optical properties of Pr3+-doped SrWO4 crystal

The polarized absorption and emission spectra of Pr³⁺ ions in SrWO₄ single crystals were investigated at room temperature. The standard and modified Judd–Ofelt theories have been applied to analyze the polarized absorption spectra to determine the spectroscopic parameters, including the Judd–Ofelt intensity parameters Ω_t (t=2,4,6), radiative transition probabilities, radiative lifetimes and branching ratios. The stimulated emission cross sections and fluorescence lifetimes of the promising laser level were obtained. PACS 78.55.Hx; 42.70.Hj; 78.20.-e     

Perturbation of the radiative lifetimes of rovibronic levels of the nl complex of terms of a diatomic molecule

Within the framework of a sufficiently general nonadiabatic model taking into account the interaction of an arbitrary finite number of electronic states and not requiring the smallness of a perturbation parameter, expressions have been obtained for the radiative lifetimes of the rovibronic levels of states of the nl complex of terms of a diatomic molecule. It is shown that the determination of ratios of the nonadiabatic and adiabatic radiative lifetimes for the rovibronic levels can be reduced to the solution of two independent problems (the determination of ratios of the adiabatic values of radiative lifetimes for the mutually perturbing states and determination of the expansion coefficients of the wave functions of rovibronic states in the Born-Oppenheimer basis set of wave functions) when the rovibronic states are perturbed by only a single rovibrational level of each electronic state or by an arbitrary number of rovibrational states of each electronic state provided that the potential curves of the combining states are similar and the dipole moments of electronic transitions weakly depend on the internuclear separation (which is quite a case for highly excited electronic states). To illustrate the efficiency of using the expressions obtained, the perturbations of the radiative lifetimes of rovibrational levels of the I ¹Π _g ^? and J ¹Δ _g ^? states of the 3d complex of terms of the H₂ molecule were considered.     

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.     

Multiconfiguration Dirac-Hartree-Fock calculations of transition rates and lifetimes of the eight lowest excited levels of radium

The multiconfiguration Dirac-Hartree-Fock (MCDHF) model has been employed to calculate the transition rates between the nine lowest levels of radium. The dominant rates were then used to evaluate the radiative lifetimes. The decay of the metastable 7s7p³P₀ state through 2-photon E1M1 and hyperfine induced channels is also studied.     

理论研究OH+离子电子态光谱及跃迁性质

采用高精度的内收缩多参考组态相互作用方法（icMRCI）计算OH⁺离子基态和低激发态的势能曲线和A³П-X³Σ^-跃迁体系的跃迁偶极矩。计算过程中考虑了能量的Davidson修正（+Q）效应和标量相对论修正。根据势能曲线,通过求解核的一维Schrödinger方程得到OH⁺的光谱参数。通过计算A³П-X³Σ^-体系的跃迁偶极矩研究这一跃迁体系的Einstein系数、F-C因子。研究了A³П（ν'=0~6）态的跃迁辐射寿命,结果显示其数量级为10^-6 s。     

Spectroscopy of YVO4:Ho3+ crystals

Crystals of YVO₄:Ho were grown by the Czochralski method. The structure of the low-energy levels of Ho³⁺ has been estimated experimentally. Intensity parameters, radiative lifetimes, and branching ratios have been calculated in the framework of the Judd–Ofelt theory. The influence of temperature on luminescence lifetimes has been investigated. The calculated nonradiative transition rate was compared with the energy-gap law. The potential laser gain for the ⁵ I ₇–⁵ I ₈ transition has been estimated. Received: 27 June 2001 / Final version: 10 December 2001 / Published online: 7 February 2002     

Crystal growth, Judd-Ofelt analysis and fluorescence properties of Tm: CaNb2O6 crystal

Tm³⁺-doped CaNb₂O₆ single crystal was successfully grown by the Czochralski technique. Based on the Judd-Ofelt theory, three spectroscopic parameters Ω_t (t=2,4,6), radiative transition probabilities, radiative lifetimes, branching ratios and oscillator strengths were obtained according to the absorption spectra and the fluorescence spectra. Both the radiative lifetimes corresponding to the ³F₄→³H₆ transition for the bulk and the powder samples were recorded, and the final value of the radiative lifetime was obtained to be 2.25 ms, which indicates the existence of the luminescence re-absorption in the bulk sample. The corresponding quantum efficiency of the ³F₄ level was calculated to be 96%.     

Optical study of erbium-doped La3Ga5.5Ta0.5O14 single crystal

Single crystals of erbium-doped La₃Ga_5.5 Ta_0.5O₁₄, grown by the Czochralski method, have been investigated using methods of optical spectroscopy. Room-temperature absorption spectra were analysed in the framework of the Judd-Ofelt theory. Radiative transition rates, radiative lifetimes and luminescence branching ratios for luminescent levels of Er³⁺ have been evaluated and compared to measured luminescence intensities and lifetimes. The laser potential associated with the ⁴I_13/2-⁴I_15/2 transition near 1.55 μm has been assessed. It has been concluded that La₃Ga_5.5 Ta_0.5,O₁₄:Er crystal is an intermediate gain laser material exhibiting strong inhomogeneous broadening of absorption bands, advantageous for optical pumping with laser diodes.     

Spectroscopic analysis of Er transition in Mg/Er-codoped LiNbO3 crystal

We present a Judd-Ofelt spectroscopic analysis on the Mg/Er-codoped congruent lithium niobate (LiNbO₃) crystals. The Judd-Ofelt model is applied to the room temperature unpolarized absorption intensities of Er³⁺ ions on eleven transition bands to determine their intensity parameters: Ω₂=2.36×10⁻²⁰ cm², Ω₄=0.76×10⁻²⁰ cm², Ω₆=0.30×10⁻²⁰ cm² in Er:LiNbO₃ crystal heavily codoped with MgO. The radiative lifetime of ²H_9/2 becomes longer when MgO is added into Er:LiNbO₃ crystal. The experimental lifetimes are obtained using microsecond time-resolved spectra at 400 nm femtosecond pulse excitation to predict radiative quantum efficiency. Combining higher radiative quantum efficiency with longer radiative lifetime, we conclude that Mg/Er-codoped LiNbO₃ crystals are more suitable than Er: LiNbO₃ ones in laser materials.     

Optical properties of Er:SrMoO4 single crystal

Er³⁺:SrMoO₄ crystal of high optical quality was grown by the Czochralski method. The room temperature polarized absorption and emission spectra together with the lifetime decay curve were measured. Based on the Judd-Ofelt theory, three intensity parameters, radiative transition rates, radiative lifetimes and fluorescent branching ratios, were obtained. Emission cross-section and gain cross-section around 1.54 μm were also obtained.     

Unusual Light Spectroscopic Properties of a 2-Pyridone-Based Multi-Ring-Fused Fluorescent Scaffold

UV-VIS absorption and fluorescence spectroscopic properties of six related polyaromatic 2-pyridones have been studied. Excitation of the lowest and rather weak and structure-less transition [ε _max (430 nm)?≈?3,000 mol^?1dm³cm^?1] gives rise to a broad fluorescence band in the visible region, for these compounds. These S ₀ ? S ₁ transitions are compatible with symmetrically forbidden transitions, promoted by intensity borrowing, as is revealed by fluorescence depolarisation data. With one exception, all compounds exhibit strong fluorescence, with quantum yields in glycerol varying between 40% and 70%. The corresponding fluorescence lifetimes range from 11 ns to 17 ns, while the radiative lifetimes are very similar (≈26 ns), for all compounds. Interestingly and rarely observed, the calculated radiative lifetimes for the weak absorption band are significantly longer, i.e. between 37 and 40 ns.     

INTENSITY STUDY OF LIF SPECTRUM FOR THE B0u→X0g SYSTEM OF A TELLURIUM NATURAL SAMPLE

The fluorescence spectrum of a tellurium sample in its natural isotopic abundance, induced by the 4764.8 Å line of an argon ion laser is studied. The study of natural tellurium samples allows us to bring out and analyze the intensity of three fluorescence series not previously reported. Photographic plates and densitometric techniques were used when recording experimental intensities. The radiative transition probabilities for the observed fluorescence series were calculated by using hybrid Perturbed-Morse-Oscillator (PMO)-Rydberg–Klein–Rees (RKR)- Long Range potential energy curves for the B0⁺_u and X0⁺_g states and a function for the transition dipole moment in the framework of the r-centroid approximation. Radiative lifetimes of the rovibrational levels for the upper state pumped by the laser line have also been calculated. The transition probabilities and lifetimes are in good agreement with the corresponding observed measurements usually within the experimental uncertainty.     

Conversion of infrared radiation into visible emission in NaY(WO4)2:Yb, Ho crystal

The spectroscopic characteristics and fluorescence dynamics for Yb³⁺/Ho³⁺:NaY(WO₄)₂ crystal were investigated. The parameters of oscillator strengths, the spontaneous transition probabilities, the fluorescence branching ratios, the radiative lifetimes and the stimulated emission cross sections have been calculated based on Judd-Ofelt theory and Füchtbauer-Ladenburg method. The energy transfer efficiency from Yb³⁺ to Ho³⁺ was 65.85%. The green emission (530-570 nm) corresponding to (⁵F₄, ⁵S₂)→⁵I₈ transition, red emission (640-670 nm) due to ⁵F₅→⁵I₈ transition and NIR emission (740-770 nm) attributed to (⁵F₄, ⁵S₂)→⁵I₇ transition were observed on 974 nm excitation at room temperature. Under low pump power, the intensity of green light emission is weaker than that of the red light, while under high pump power, the case is on the contrary. The upconversion is based on the two-photon process either the energy transfer from Yb³⁺ ions or by the excited state absorption. The proposed mechanisms of upconversion emissions were provided.     

Fluorescence features of Sm ions in Na2SO4-MO-P2O5 glass system—Influence of modifier oxide

Na₂SO₄-P₂O₅:Sm³⁺ glasses mixed with three different alkaline earth modifier oxides viz., MgO, CaO and BaO were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature; the Judd-Ofelt theory was successfully applied to characterize these spectra. From this theory, various radiative properties like transition probability A, branching ratio β_r, the radiative lifetime τ_r, for various emission levels in the spectra of these glasses have been determined and reported. An attempt has also been made to throw some light on the relationship between the structural modifications and luminescence efficiencies in the change of scenario for modifying oxides in the glass network.     

Transition probabilities, oscillator strengths and lifetimes for singly ionized magnesium

The electric dipole transition probabilities, oscillator strengths and lifetimes have been calculated using the weakest bound electron potential model theory (WBEPMT) for singly ionized magnesium. In the calculations both multiplet and fine structure transitions are studied. We have employed both the numerical Coulomb approximation (NCA) method and numerical non-relativistic Hartree-Fock (NRHF) wave functions for expectation values of radii. The calculated oscillator strengths and lifetimes have been compared with MCHF results given by Fischer et al. (2006). A good agreement has been obtained with the MCHF results. Moreover, some new transition probabilities, oscillator strengths and lifetime values, not existing in the data bases for highly excited levels in singly ionized magnesium, have been obtained using this method.     

Lifetimes of metastable levels in Ar II

We report on a calculation of five lifetimes of metastable levels in Ar II, obtained with a relativistic Hartree-Fock method in which most of the intravalence correlation is represented within a configuration interaction scheme while core-valence correlation is described by a core-polarization model potential with a core-penetration corrective term. The quality of the calculation has been assessed through an experimental determination of the radiative lifetime of the metastable 3d ⁴F_9/2 level. The experiment was performed with a laser probing technique on a stored ion beam at the CRYRING of Stockholm.Received: 16 January 2004, Published online: 30 March 2004PACS: 31.10. + z Theory of electronic structure, electronic transitions, and chemical binding - 32.70.Cs Oscillator strengths, lifetimes, transition moments     

Investigation on luminescence properties of Nd ions in alkaline-earth titanium phosphate glasses

Nd³⁺ ions doped alkaline-earth titanium phosphate glasses were prepared by using the conventional melt quenching method. Absorption spectra were recorded and oscillator strengths of the transitions were calculated using area under the absorption bands. The energy level analysis was carried out by using free-ion Hamiltonian model. The three host dependent Judd-Ofelt intensity parameters, Ω_λ (λ = 2, 4, and 6) were used to elucidate the structure of glassy matrix around Nd³⁺ ion as well as to determine the ⁴F_3/2 metastable state radiative properties such as radiative transition probabilities, branching ratios and radiative lifetimes. The decay curves of all the three glasses show single exponential behavior. The discrepancy between the experimental and calculated lifetimes of emitting level was attributed to multiphonon relaxation. The achieved high quantum efficiencies for the ⁴F_3/2 level indicate efficient laser emission at 1.06 μm in these glass systems.