Calibration of the R ruby fluorescence lines in the pressure range [0-1 GPa] and the temperature range [250-300 K]

Abstract

The pressure range [&1 GPa] and the temperature range [250–300 K] are commonly used in many science fields like biology, agro-chemistry, pharmacology, or geology. In this paper, the calibration of the ruby R lines of fluorescence is performed in these pressure and temperature ranges, using the melting curve of pure water. The linear shifts of ruby peaks are equal to ?0.140cm^?1/K and ?0.768cm^?1/kbar with R₁, and to ?0.137cm^?1/K and ?0.779 cm^?1/kbar with R₂. The accuracy of pressure measurements can be as good as ± 10MPa if the temperature is known with ±0.5 K. Such a precision is achieved if: (1) the position of each peak is determined using an inversion method; (2) daily shifts of the spectrometer are corrected before each acquisition; (3) peak positions of each ruby are known at ambient pressure and temperature.     

The DV-Xα Calculations of Optical Spectra and Their Pressure-Induced Shifts for Ruby

The R line and U band at normal pressure and their pressure-induced shifts of ruby have been calculated by making use of the SCF embedded-cluster discrete variational (DV-X_α) method. The calculated results of the spectral pressure-induced shifts of ruby by making use of the crystal-field theory have also been given. The results of the first-principle calculations are in very good agreement with the experimental data and the calculated results by using crystal-field theory. The results of local lattice relaxations around the Cr³⁺ ion are obtained by the DV-X_α calculations.     

90 GPa（准）静水压力的产生及压力分布的测量

 本文使用固态氩做传压介质，在自制的Mao-Bell型金刚石对顶砧装置中获得了90 GPa的准静水压。通过测量样品室内不同位置上红宝石荧光R₁线的频移来确定压力分布。实验结果表明在80 GPa以下，样品室内不同位置上的压力与平均压力（p）的差Δp很小，最大的Δp/p不超过1.5%。在90 GPa时，红宝石的荧光R线与常压的很相似。这表明利用固态氩做传压介质可以获得接近100 GPa的准静水压。此外，对红宝石荧光光谱中位置在14 938 cm^-1和14 431 cm^-1两条谱线随压力的变化情况也作了讨论，并由此得出结论，14 938 cm^-1这条线也可用来标定压力。     

红宝石R＇、B线及U、Y带压力移位的理论计算

基于电子径向波函数在加压下扩展的概念，把Ｂ、Ｃ、Ｄｑ、ξ等参量表示成线性压缩ｋ＼的函数，并进一步考虑三角场作用，理论计算了红宝石Ｒ＇、Ｂ线及Ｕ、Ｙ带的光谱压力移位，结果与实验数据符合很好。     

Theoretical calculations of the pressure-induced blue and red shifts of spectra of MgO:Cr3+

The pressure-induced blue and red shifts of spectra of MgO:Cr³⁺ can be understood in a unified way by using the concept of electron cloud expansion under pressure. The blue shifts of two bands and the red shift of the R line of MgO:Cr³⁺ are calculated with only three common parameters. The agreement with the experimental data is satisfactory.     

Pressure-Induced Shifts of R, R', and B Line-Groups and Ground-State Zero-Field-Splitting of Ruby

By means of improved ligand-field theory, the “pure electronic” presure-induced shifts (PS's) and the PS's due to electron-phonon interaction (EPI) of the R₁, R₂, B₁, B₂, B₃, and R'₃ lines and the ground-state zero-field-splitting of ruby have been uniformly calculated. The calculation results are in very good agreement with all the experimental data. At normal pressure, ruby is a crystal with very strong crystal field. Thus, the admixture of |t₂²(³T₁)e⁴T₂〉and |t³₂²E〉bases in the wavefunction of R₁ level of ruby is small at normal pressure, and it gradually decreases with increasing pressure, which causes the R₁-line PS of ruby to monotonously red shift with approximate linearity. The combined effect of the pure electronic PS of R₁ line and the PS of R₁ line due to EPI gives rise to the total PS of R₁ line. The analyses and comparisons among the features of R₁-line PS's of three laser crystals (ruby, GSGG:Cr³⁺ and GGG:Cr³⁺) have been made, and the origin of their difference has been revealed.     

On a parametrization for solids under hydrostatic pressures

A newly developed parametrization successfully used to calculate the hydrostatic pressure dependence of the Cr³⁺ spectra of ruby is shown to be useful also for describing some cases of hydrostatic pressure shifts of Van Vleck susceptibilities and Knight shifts.     

红宝石R'、B线及U、Y带压力移位的理论计算

基于电子径向波函数在加压下扩展的概念,把B、C、Dq、ξ等参量表示成线性压缩κ\的函数,并进一步考虑三角场作用,理论计算了红宝石R''、B线及U、Y带的光谱压力移位,结果与实验数据符合很好.     

Improved Ligand-Field Theory with Effect of Electron-Phonon Interaction

Traditional ligand-field theory has to be improved by taking into account both “pure electronic” contribution and electron-phonon interaction one (including lattice-vibrational relaxation energy). By means of improved ligand-field theory, R₁, R₂, R₃', R₂', and R₁' lines, U band, ground-state zero-field-splitting (GSZFS), and ground-state g factors of ruby and/or GSGG:Cr³⁺ as well as thermal shifts of GSZFS, R₁ line and R₂ line of ruby have been calculated. The results are in very good agreement with the experimental data. Moreover, it is found that the value of cubic-field parameter given by traditional ligand-field theory is inappropriately large. For thermal shifts of GSZFS, R₁ line and R₂ line of ruby, several conclusions have also been obtained.     

Equations of state for Cu,Ag, and Au and problems with shock wave reduced isotherms

Thermophysical data at low pressure are used to constrain a thermodynamic model for equations of state and all the other thermophysical properties in wide ranges of pressure and temperature. Comparisons with shock wave reduced isotherms show strong deficiencies in the models used in the data reductions. A revision in the evaluation of static high-pressure X-ray diffraction data for Cu and Au together with data for ruby luminescence line shifts from the literature lends further support to some recent refinements of the ruby pressure scale.     

Tunable optical properties of nano-Au on vanadium dioxide

The optical properties of Au nanoparticles deposited on thermochromic thin films of VO₂ are investigated using spectroscopy. A localized modification on the transmittance spectrum of VO₂ film is formed due to the presence of Au nanoparticles which exhibit localized surface plasmon resonance (LSPR) in the visible-near IR region. The position of the modification wavelength region shows a strong dependence on the Au mass thickness and shifts toward the red as it increases. On the other hand, it was found that the LSPR of Au nanoparticles can be thermally tunable because of the thermochromism of the supporting material of VO₂. The LSPR wavelength, λ_SPR, shifts to the blue with increasing temperature, and shifts back to the red as temperature decreases. A fine tuning is achieved when the temperature is increased in a stepwise manner.     

超高压下红宝石荧光R线的猝灭压力与入射激发线波长的关系

 分别使用固态氩和体积比为4∶1的甲醇-乙醇混合溶液做传压介质，测量红宝石在这两种介质中的荧光光谱随压力的变化。首先发现在超高压下红宝石荧光R线的压致猝灭与入射激发线波长以及高压样品室内的静水压程度有关。实验结果表明：入射激发线的波长越长，荧光R线的猝灭压力越低；对同一激发线波长，静水压程度差，猝灭压力高。这一现象归因于红宝石吸收谱中U带和Y带随压力的蓝移。     

高压低温条件下固态氩和4∶1甲醇-乙醇混合物传压介质的传压特性

 在高压低温（77 K）条件下，利用红宝石荧光测压方法，系统地研究了金刚石对顶砧装置中固态氩和4∶1甲醇-乙醇混合物的传压特性。通过测量不同位置上红宝石荧光R₁线的频移，确定了样品室内的压力分布。实验结果表明：在0~16 GPa的压力范围内，固态氩介质中反映介质非均匀性程度的|Δp/p|<3%、σ_p/p<2%，均在室温静水压条件下所允许的范围之内。红宝石荧光R线除随压力变宽外，与常压的很相似，表明固态氩在高压低温条件下是良好的传压介质。与之相比，4∶1甲醇-乙醇介质在77 K低温下的传压特性明显差于固态氩，已不适合作传压介质。     

Thermal Shifts and Electron—Phonon Interactions of ^4T2 and ^4T1 Broad Bands for Ruby

For the first time,by taking into account all the irreducible representations and their components in the electron-phonon interaction (EPI) as well as all the levels and the admixtures of wavefunctions within d^3 electronic electron-phonon interaction (EPI) as well as all the levels and the admixtures of wavefunctions within d^3 electronic configuration,the values of parameters in expressions of Raman and optical-branch terms of thermal shifts (TS) due to EPI for three levels,^4T2 band and ^4T1 band of ruby have been evaluated;the contributions to TS of ^4T2 and ^4T1 broad bands from thermal expansion have also been calculated;and then,the TS of the peak energies of ^4T2 and ^4T1 broad bands have been calculated.The results are in satisfactory agreement with observed data.The values of single-electron reduced matrix elements representing the strengths of EPI of ^4T2 and ^4T1 bands have respectively been determined.For TS of the peak energies of ^4T2 and ^4T1 bands,it is found that the contribution to TS from the second-order term in EPI Hamiltonian is dominant;TS due to EPI of acoustic branches are over two times as much as those of optical branches,and both of them increase rapidly with temperature;the neighbor-level term is insignificant;the contribution to TS from thermal expansion is specially important,and all the three terms of TS of ^4T2 or ^4T1 band are red shifts.     

A computational study of the linear and nonlinear complexes of FArCCH···N2

Linear and nonlinear weakly bound complexes of the metastable argon-containing compound FArCCH and N₂ were predicted to be stable from ab initio computations at the MP2/6-311++G(2d,2p) level of theory. Both complexes were found to have similar interaction energies and they exhibit red shifts of the C–H stretch, blue shifts of the Ar–C stretch and red shifts of the F–Ar stretch, in the same order as the stabilities. These effects are rationalized by considering changes in orbital occupancies on complexation, which are brought about by a combination of the intermolecular electrostatic interaction and charge density transferred from the N₂ molecule to the argon-containing molecule.     

Luminescence of Nile red as indicator of composition of nanoparticles from diketonate complexes of trivalent metals

We study the sensitization of fluorescence of Nile red in nanoparticles formed in aqueous solutions of complexes of Al, In, Sc, and Lu with DBM, DBM, and phen and of complexes of In with MBTA and phen. We show that, at concentrations of Nile red of 2–50 nM and complexes of 10–30 μM, the fluorescence intensity of Nile red in aqueous solutions increases by 1.5–2 orders of magnitude compared to its fluorescence in H₂O. We find that, at these concentrations of Nile red in solutions of complexes Al, the dye is completely contained in nanoparticles from these complexes. We show that Nile red molecules are inhomogeneously distributed in nanoparticles from complexes and, upon the completion of the formation of nanoparticles, dye molecules tend to be localized in regions of nanoparticles formed from diketonate complexes M(diketone)₃phen (M is Lu or In) and Al(DBM)₃. Upon the localization of Nile red in these regions, the maximum of its fluorescence spectrum shifts toward ∼600 nm and, upon the penetration of Nile red into nanoparticles from Sc complexes, the shift of the maximum of its fluorescence spectrum compared to the spectrum in water does not exceed 10 nm. The shifts of the spectra are collated with the ability of ions to form diketonate and hydroxy diketonate complexes. We demonstrate that the fluorescence of Nile red is efficiently sensitized, not only upon its penetration into nanoparticles formed from complexes, but also upon its adsorption on the nanoparticle surface when Nile red molecules are introduced in solutions of already formed nanoparticles.     

Starting stress for the onset of dislocation motion in ruby single crystals

For the purpose of preparing ruby single crystals with a high degree of structural perfection, the evolution of their structural state is investigated using four-point loading at T=1490°C and chemical etching pits. The starting stress τ_st for the onset of the dislocation motion is measured. The regularities of the arrangement of dislocations in single-crystal samples of ruby are established. The starting stress for the onset of the dislocation motion is found to be τ_st=2 MPa. The results obtained make it possible to determine the optimum parameters of thermomechanical treatment of the single crystals and, in the future, to solve the problem of their longterm serviceability.     

Synthesis and characterization of nano silver ferrite composite

We report the synthesis of nano sized silver ferrite composite having the empirical formula AgFeO₂ by a co-precipitation method. The resulting powders are thin platelets, transparent and a rich ruby red in color in transmission. The X-ray diffraction (XRD) powder data consisted of only nine reflections, and the analysis showed the unit cell to be rhombohedral. The powders showed extensive XRD line broadening and the sizes of the crystals are calculated to be in the range 4-36.5 nm. The morphology of the silver ferrite composite studied using scanning electron microscope showed nano sized particles. The particle size is found to increase with increase in annealing temperature. The magnetic behavior, measured using a vibrating sample magnetometer, indicated a change from paramagnetic to ferromagnetic with increase in particle size.     

Self-transparency in ruby with allowance for level degeneracy

Propagation of a “self-transparent” pulse in ruby at the frequency of the R₁ line is considered theoretically in the presence of degeneracy of the transitions. The transmission of a ruby sample 12 cm long is calculated and it is shown that it can be quite high, 0.7, differing greatly from the transmission in a model in which degenerate transitions are regarded as independent.     

Pseudo-nonlinear and athermal lensing effects on transverse properties of Cr based solid-state lasers

Several experiments (time-resolved Z-scan experiments based on pulsed and CW pump lasers, time-resolved divergence diagnostics) have been performed to examine and clarify the question of the converging or diverging population lensing effect occurring in a Cr^3 +:Al₂O₃ ruby laser. The dynamics of the laser far-field divergence of such a laser indeed indicated initially a diverging effect while Z-scan measurements conclude to a converging one. The origin of this discrepancy is thus analysed and elucidated here by introducing the general concept of correlation collapse between the centre and the wings of a laser beam having some clipping.