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

Abstract

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.

Temperature and stress induced changes of the vibrational response of cubic and rhombohedral 10mol%Sc2O3–1mol%CeO2–ZrO2 ceramics

“…Thought the bands in the 1000-2000 cm −1 range do not represent the vibrational response of ions in zirconia lattice, they still can be easily used to identify both the presence of the cubic and rhombohedral phases and help detect residual stress existing in the material due to temperature or pressure effects. The approach is similar to the one used in alumina to detect stresses using well known R-line peak positions which appeared because of the transitions between the ground state of the Cr 3+ impurity ion and its first excited state, when the material is excited with an citation source such as a laser [31,32]. Fig.…”

Ex‐Situ Stress Measurements in Polycrystalline Ceramics Using Photo‐Stimulated Luminescence Spectroscopy and High‐Energy X‐Rays

“…This procedure is based on GA for the optimization of the fit. The details of the spectral analysis methodology of the R ‐lines and vibronic bands using GA are presented in our earlier work 7 …”

“…Our earlier work presents the experiments and results of uniaxial compression tests on single crystal ruby specimens to investigate and quantify the stress dependency of peaks in the vibronic bands 6 . This led to the development of a deconvolution and fitting methodology using genetic algorithms (GA) 7 to identify and monitor the numerous peaks in these bands. In the study presented here, the PS coefficients of polycrystalline alumina were obtained by examining the shifts of the R ‐lines as well as multiple peaks within the vibronic bands when the specimens were under compression.…”

Quantifying Alumina Nanoparticle Dispersion in Hybrid Carbon Fiber Composites Using Photoluminescent Spectroscopy

“…In alumina's crystal structure, the trace (Cr 3+ ) is located at a site with trigonal distortion. This distortion, as well as the spin-orbit coupling, results in doublet fluorescence peaks, the higher intensity peak known as R1 and the lower intensity peak known as R2 [30,31].…”