Spectrum Of Ruby Research Articles

Chromaticity coordinates of ruby based on first-principles calculation

Understanding the local atomic configuration is crucial for studying phosphor materials. Their performance in many applications is strongly dependent upon their optical properties. Much experimental and theoretical effort has been made to meet the requirements. Specifically, ab-initio studies have extensively reported the absorption spectra and the multiplet energies of phosphors. However, the qualitative analysis on the emitted light has not yet been reported. In this work, we characterized the emitted light of ruby, which is a widely studied phosphor material. The absorption spectra of ruby were calculated utilizing the non-empirical discrete variational Xα (DV-Xα) and discrete variational multi-electron (DVME) software. Then, the investigation on the ( x , y ) chromaticity coordinates of was performed under the standard illuminant D65 utilizing ColorAC software, a chromaticity diagram maker. In this work, we used a ruby model cluster generated from an α-Al 2 O 3 crystal. The model consists of seven atoms, where one chromium atom surrounded by six oxygen atoms. We compared the absorption spectra obtained via simple configuration interaction (CI) and those obtained which include energy corrections called configuration dependent correction (CDC) and correlation correction (CC). We successfully reproduced the color that is observed in experiment. The chromaticity coordinates approach red region for higher concentration. The results show that the calculation with CDC-CC shows better agreement with experiment. This research confirms the non-empirical calculations based on the DV-Xα and DVME methods, in the terms of emitted light. • The emitted light of α-Al2O3: Cr3+ (ruby) was characterized non-empirically. • Effects of CDC-CC correction were investigated thoroughly. • The “theoretical color” reproduced the tendency of the “experimental color”. • The calculation with CDC-CC correction shows better agreement.

On the Thermal Spectra of Ruby and Sapphire

The temperature dependence of the thermal spectra (in the range from 0.4 to 8 μm) of ruby and sapphire single crystals heated by a 10.6-μm cw electric-discharge CO2 laser has been experimentally and analytically investigated. The shape of the background of the spectral lines of impurity Cr3+ ions in ruby corresponds to the short-wavelength tail of sapphire thermal radiation. The Planck thermal spectrum of sapphire is interpreted in terms of the interaction between electrons and lattice ions in the conduction band.

Ion beam analysis of rubies and their simulants

Ion beam analysis (IBA) is a set of well known powerful analytical techniques which use energetic particle beam as a probe. Among them, two techniques are suitable for gemological analysis, i.e., Particle Induced X-rays Emission (PIXE) and Ionoluminescence (IL). We combine these two techniques for the investigations of rubies and their simulants. The main objective is to find a reference fingerprint of these gemstones. The data are collected from several natural rubies, synthetic rubies, red spinels, almandine garnets and rubellite which very much resemble and are difficult to distinguish with the gemologist loupe. From our measurements, due to their different crystal structures and compositions, can be clearly distinguished by the IL and PIXE techniques. The results show that the PIXE spectra consist of a few dominant lines of the host matrix elements of each gemstone and some weaker lines due to trace elements of transition metals. PIXE can easily differentiate rubies from other stones by evaluating their chemical compositions. It is noticed that synthetic rubies generally contain fewer impurities, lower iron and higher chromium than the natural ones. Moreover, the IL spectrum of ruby is unique and different from those of others stones. The typical spectrum of ruby is centered at 694nm, with small sidebands that can be ascribed to a Cr3+ emission spectrum which is dominated by an R-line at the extreme red end of the visible part of the electromagnetic spectrum. Although the spectrum of synthetic ruby is centered at the same wavelength, the peak is stronger due to higher concentration of Cr and lower concentration of Fe than for natural rubies. For spinel, the IL spectrum shows strong deformation where the R-line is split due to the presence of MgO. For rubellite, the peak center is shifted to 692nm which might be caused by the replacement of Mn3+ at the Al3+ site of the host structure. It is noticed that almandine garnet is not luminescent due to the idiochromatic nature of the stone.

Note: Compact optical fiber coupler for diamond anvil high pressure cells

A compact optical fiber coupler has been developed to allow transmission of light through an optical fiber to and from the high pressure region of a diamond anvil high pressure cell. Despite its small size the coupler has focusing adjustments and optics, which allows the light to be focused precisely on the sample within the pressure cell. The coupler is suitable for a wide range of optical measurements and particularly for high pressure measurements at low temperatures in cryostats with no optical windows. The use of the coupler to determine the pressure in a diamond anvil cell at 1.2 K using the ruby fluorescence spectra of ruby is demonstrated. The small size of the coupler and its construction out of nonmagnetic beryllium copper makes it suitable for use in high magnetic fields and for magnetization experiments.

The two-photon absorption spectrum of ruby and its role in distributed optical fibre sensing

The two-photon absorption spectrum and cross-section (δ) for ruby (Cr3+:sapphire) have been measured over the 0.8–1.2 μm wavelength range at 25°C. Absolute values of δ were obtained by comparing the fluorescence yield for two-photon excitation with that for single-photon excitation of the same ionic transition under identical illumination conditions. The maximum values of δ are 4.6×10−3 GM for o-polarisation and 5.9×10−3 GM for e-polarisation at 840 nm. The relevance of these measurements to distributed optical fibre sensing is briefly discussed.

Doubly resonant Raman electron paramagnetic transitions ofCr3+in ruby(Al2O3:Cr3+)

We report the Raman electron paramagnetic resonance (EPR) of ${\text{Cr}}^{3+}$ in ruby $({\text{Al}}_{2}{\text{O}}_{3}:{\text{Cr}}^{3+})$ in the ${^{4}A}_{2}$ (ground) and $\overline{E}$ (excited) states of its well-known ${R}_{1}$ emission line. Using tunable dye laser excitation within the range of the Zeeman components of ${R}_{1}$, we observe highly selective doubly resonant enhancements of the Raman EPR lines. The double resonances confirm the assignments of the Raman EPR lines, and they underscore the simultaneous occurrence of both ``in resonance'' and ``out resonance'' as visualized in the Kramers-Heisenberg quantum-mechanical picture of inelastic light scattering. The $g$ factors of the ${^{4}A}_{2}$ and $\overline{E}$ states are consistent with the observed magnetic field dependence of the Raman EPR shifts. Through the interplay of Raman effect and the sharp Zeeman components of ${R}_{1}$, the results provide clear insights into the underlying microscopic mechanism of these resonant Raman EPR spectra of ruby.

First-principles calculation of ground and excited-state absorption spectra of ruby and alexandrite considering lattice relaxation

We performed first-principles calculations of multiplet structures and the corresponding ground-state absorption and excited-state absorption spectra for ruby $({\text{Cr}}^{3+}:\ensuremath{\alpha}{\text{-Al}}_{2}{\text{O}}_{3})$ and alexandrite $({\text{Cr}}^{3+}:{\text{BeAl}}_{2}{\text{O}}_{4})$ which included lattice relaxation. The lattice relaxation was estimated using the first-principles total energy and molecular-dynamics method of the CASTEP code. The multiplet structure and absorption spectra were calculated using the configuration-interaction method based on density-functional calculations. For both ruby and alexandrite, the theoretical absorption spectra, which were already in reasonable agreement with experimental spectra, were further improved by consideration of lattice relaxation. In the case of ruby, the peak positions and peak intensities were improved through the use of models with relaxations of 11 or more atoms. For alexandrite, the polarization dependence of the U band was significantly improved, even by a model with a relaxation of only seven atoms.

Spectral Analysis of R-lines and Vibronic Sidebands in the Emission Spectrum of Ruby Using Genetic Algorithms

The advancement in spectral analysis methods for the emission spectrum of ruby has been driven by the characterization of R-line peak shifts with stress in order to establish piezospectroscopic relationships. These relationships form the basis for the development of photo-stimulated luminescence spectroscopy (PSLS) as a nondestructive method to determine the integrity of the thermally grown oxide (TGO) layer on jet engine turbine blades. Besides the measurement technique, the accuracy of PSLS in stress measurements is influenced by the spectral analysis methodology, which is the focus of this paper. Gradient-based algorithms have been used widely in the methods developed thus far. The approach of using genetic algorithms in the spectral analysis of R-lines and vibronic bands is presented here for the first time and validated with the wellknown piezospectroscopic coefficients of the R-lines. The implementation of this method has led to significant new results in the quantification of peak shifts with uniaxial stress in the vibronic bands of the spectrum. The use of genetic algorithms is instrumental in the deconvolution and fitting of the numerous peaks in these bands. Fitting statistics, such as the fitness function and number of function evaluations, were used to assess the effectiveness of the procedures used in this method.

Manipulation of Zeeman coherence in solids at room temperature: Ramsey interference in the coherent-population-trapping spectrum of ruby

Coherent population trapping (CPT) in a three-level atomic medium pumped by two subsequent short optical pulses is considered under the condition of negligible population decay from the excited optical state. It is shown that the amount of atomic population transferred to the excited state by the combined action of the pulses strongly depends on the phase of the ground-state coherence excited by the first pulse at the arrival time of the second pulse. Oscillatory behavior of optical excitation efficiency on the time delay between the pulses is predicted. It is also shown that saturating optical pulses can produce population inversion in a resonantly pumped quasi-two-level system. A class of solid materials in which the predicted phenomena can be observed at room temperature is found. It includes some rare-earth and transition-metal doped dielectric crystals where Orbach relaxation between ground-state Zeeman states is suppressed: ruby, alexandrite, and several others. On the basis of the theoretical predictions, experimental observation of Ramsey fringes in CPT spectrum of ruby is reported.

Factors Determining the Stability, Resolution, and Precision of a Conventional Raman Spectrometer

We verified the performance of a conventional Raman spectrometer, which is composed of a 30 cm single polychromator, a Si based charge-coupled device (CCD) camera, and a holographic supernotch filter. For that purpose, the time change of the peak positions of Raman spectra of naphthalene and fluorescence spectra of ruby (Cr-doped Al(2)O(3)) were monitored continually. A time-dependent deviation composed of two components was observed: a monotonous drift up to 0.4 cm(-1) and a periodic oscillation with a range of 0.15 cm(-1). The former component was stabilized at approximately 2000 s after the CCD detector was cooled, indicating that incomplete refrigeration of the CCD detector induced the drift. The latter component synchronized with the periodic oscillation of the room temperature, indicating that thermal expansion or contraction of the whole apparatus induced this oscillation. The implemental deviation is reduced when measurements are conducted using a sufficiently cooled CCD detector at a constant room temperature. Moreover, the effect of the room temperature oscillation is lowered in a spectrum acquired over a duration that is longer than one cycle of this oscillation. Applying the least squares fitting method to carefully measured spectra enhanced the precision of the determination of the peak position to 0.05 cm(-1) using the spectrometer with pixel resolution of 1.5 cm(-1).

Magnetostructural effects and phase transition inCr2O3under pressure

We have successfully calculated the electronic and structural properties of chromia (Cr_2O_3) in the Local Spin Density Approximation (LSDA). We predict a transformation from the corundum to the Rh_2O_3(II) structure around 15 GPa in the anti-ferromagnetic (AFM) phase as well as in the paramagnetic (PM) insulating state which occurs above the Neel temperature (T_N). This transition is relevant to interpreting the optical anomalies observed in the absorption spectrum of ruby under pressure. We have modeled the structural properties of the PM state using a Landau-like expansion of the magnetostriction energy. This treatment correctly describes the structural anomalies across T_N in the corundum phase and indicates that the AFM and PM insulating states should have distinct compressive behaviors.

Theoretical calculations of pressure-induced shifts of the entire energy spectrum of ruby

The d3 ions in trigonal crystal fields are considered. On the basis of the expansion of the electron wavefunctions under pressure, the expressions for the parameters Dq, B, C, K, K' and zeta as functions of the linear compression ratio chi are derived, and the complete d3 energy matrix in trigonal field is constructed. With the P-chi dependence, by diagonalization of this matrix to fit only the experimental data of the red shifts of ruby R1 line under quasihydrostatic pressure, the values of three parameters for the pressure shift (S0, D1 and t) are determined. Then, the values of Dq, B, C, K, K' and zeta at various pressures are evaluated, and the pressure shifts of the entire energy spectrum of ruby are theoretically calculated uniformly by diagonalization of the complete d3 matrix. The contributions of changes of Dq, B, C, K, K' and zeta to the R1 and R2 red shifts and the pressure-induced change in the R1-R2 splitting are obtained. The calculated results of the pressure shifts are in good agreement with all the experimental data of the R-, R'- and B-line groups and U and Y bands. A discussion is given and conclusions drawn.

High pressure spectroscopy of heavily doped ruby

Measurements include studies of effect of hydrostatic pressure, up to 80 kbar, on fluorescence spectra of ruby, especially the pressure dependence of the energy of the lines related to fluorescence of paired Cr 3+ ions. We have considered the high pressure spectroscopy experiments as effective tool for identification of the lines and investigation of the exchange interaction

A ceramic-type diamond anvil cell for optical measurements at high pressure in pulsed high magnetic fields

A diamond anvil cell made of stabilized zirconia ceramic for high-pressure experiments under a pulsed high magnetic field is described. As an application, the magneto-optical spectra of ruby have been obtained at 77 K up to 7 GPa and 33 T, showing the Zeeman splitting of the fluorescent lines, R1 and R2.

Relationship of the ruby spectrum to the geometry of the chromium(III) environment

Relationship of the ruby spectrum to the geometry of the chromium(III) environment

Analysis of the absorption spectrum of ruby at high pressures.

It is shown that at high pressures, results of absorption measurements are inconsistent with R-line fluorescence data. The observed constancy of ${R}_{1}$-${R}_{2}$ splitting under hydrostatic conditions is supported by crystal-field analysis. The present findings suggest the need for absorption measurements in ruby crystals under more well-defined stress conditions.

Strong‐field scheme for C (d3) and the Spectra of Ruby and Cr2O3

AbstractIn order to calculate the energy spectra of Cr3+ ions in a C3v symmetry crystal field, a radial orbit function is used for the d‐electrons in bounded ions having a form between the SCF wave functions of Richardson and Watson. In addition the complete strong field matrices of C(d3) are built up for the first time by a simplified strong‐field scheme, in which the Griffith standard bases of the O double group are taken as the starting point. Then the absorption spectra (including the spin‐allowed and spin‐forbidden spectra) of Cr3+ in ruby and Cr2O3 crystals are calculated. The theoretical results, with consideration of vibronic, are quite consistent with experiments. Thus the mechanism of the absorption spectra of Cr3+ in these two crystals is well explained. This scheme of calculating spectrum parameters by radial orbits greatly reduces the number of fitting parameters. This simplified strong‐field scheme can be extended to any dn system and any subgroup of Oh.

Theoretical calculations of pressure-induced blue and red shifts of spectra of ruby

On the basis of the concept of expansion of the electron radial wavefunction under compression, using expressions for B, C and Dq as functions of the linear compression ratio kappa and taking into account the configuration interaction (through the Coulomb interaction) and the interaction (through the trigonal crystal field) between t2g3 2Eg and t2g3 2T1g mixed states, the authors calculate theoretically the pressure-induced shifts of the R, R' and B lines and the U and Y broad bands of the spectra for ruby. The results agree well with all the experimental data over a wide pressure range.

Theoretical calculations of pressure-induced shifts of R, R′, B lines and U, Y bands of ruby

Using the conception of expansion of the electron radial wavefunction under compression and the expressions of B, C, and Dq as functions of the linear compression ratio κ, taking into account the configuration interaction and the interaction between t 2 3 2E and t 2 3 2T 1 mixed states through the trigonal field, the pressure-induced shifts of the spectra of ruby were calculated. Results agreed well with all the experimental data over a wide renge of pressure.

Erratum: d-orbital theory and high-pressure effects upon the EPR spectrum of ruby

Erratum: d-orbital theory and high-pressure effects upon the EPR spectrum of ruby