Line shapes of narrow optical bands: Infrared absorption by<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>U</mml:mi></mml:math>centers and heavier impurities in alkali halides

Lagos, Miguel; Asenjo, Felipe A.; Hauyón, Roberto; Pastén, Denisse; González, H Jesus; Henríquez, Ricardo; Troncoso, Roberto E.

doi:10.1103/physrevb.77.104305

Cited by 6 publications

(22 citation statements)

References 13 publications

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“…The lineshape function has been proven in the recent literature to be given by the integral expression 7−9,11 where ℏ ck is the photon energy, E is the energy difference of the two electronic states involved in the transition, a is essentially the bond length, and v s is the mean speed of sound of the acoustic modes of vibration of the medium. The adimensional constants α and β, and the adimensional dummy time τ are given bywhere Δ F is the bond mean force variation upon excitation, ρ is the density, k B is the Boltzmann constant, and T is the temperature.…”

Section: Theorymentioning

confidence: 99%

“…For the simplest case of octahedral coordination (OC) of the optically active orbital, they readwith q D being the Debye wavevector of the acoustic waves, aq D = (12π 2 ) 1/3 , andThe second term on the right-hand side of eq 1 for F (ℏ ck ; T ), containing the delta function, is the zero-phonon line, and the first one is the phonon-broadened distribution. The lineshape function F (ℏ ck ; T ) is normalized as 7−9 and hence the relative contribution of zero-phonon processes to the total is I ZPL = exp[−α J (∞; T )].…”

Section: Theorymentioning

confidence: 99%

“…If the theoretical curve reproduces well the physics of the radiation field interacting with the target, then the error is given by the statistical dispersion of the experimental points along the curve that bests the fit, instead of its whole breadth. 7−11…”

Section: Introductionmentioning

confidence: 99%

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Fourier Transform Spectrometry with Fourier Analysis of the Interferogram as Just an Optional Tool

2018

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Fourier transform spectrometers replace the traditional dispersive frequency analyzer by a Michelson interferometer. The spectrum is the Fourier transform of the interferogram constituting the raw output. The method is a primary tool for chemical analysis because it has decisive advantages over the dispersive one for analyzing infrared electromagnetic radiation (Fourier transform infrared, FTIR). A new procedure for dealing with the raw interferometric output of the instrument, not needing Fourier transformation and having additional advantages, is put forward here. It rests on recent advances in the theory of the interaction of matter with electromagnetic radiation yielding first principles analytic expressions for the Fourier transform of the spectral lineshapes, which can be fitted directly to the experimentally measured interferogram. The relevant physical information, as the integrated intensities of the electronic transitions and their net energy release, not affected by Stokes shifts, is readily obtained in the fitting procedure. Ulterior analysis of the spectra, introducing phenomenological standard interpolation functions to deconvolute and integrate peaks, becomes unnecessary. Both methods, standard FTIR and the one outlined here, demand little computer time and can be used simultaneously with synergistic effects.

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Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

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Fourier Transform Spectrometry with Fourier Analysis of the Interferogram as Just an Optional Tool

2018

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“…In general, the lineshape function is given by the function [2,3,15,16] arXiv:1704.04120v1 [cond-mat.mtrl-sci] 12 Apr 2017…”

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confidence: 99%

“…where ck is the photon energy, E the energy difference of the two electronic states involved in the transition, a is essentially the bond length, and v s the mean speed of sound of the acoustic modes of vibration of the medium. The general form of the auxiliary functions J(τ ; T ) and I(τ ) depends on the symmetry of the surroundings of the optically sensitive orbital [16]. For the simplest case of octahedral symmetry they read…”

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High precision energy measurements from the analysis of wide spectral features. Application to the fluorescence of YAG:Ce 3+

Lagos

Paredes

Retamal

2017

Journal of Photochemistry and Photobiology A: Chemistry

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Advantage is taken of a complete and precise experimental study of the luminescent properties of yttrium aluminium garnet doped with Ce 3+ , previously accomplished by other authors, to confirm the accuracy of the invoked theoretical methods for dealing with the realistic calculation of the electromagnetic spectra of condensed phases. The fluorescent spectra at T = 0 and T = 250 K of YAG:Ce 3+ were calculated with no adjustable parameter, giving complete agreement with experiment. The energy released by the electronic transitions was determined with precision better than 5% the full width at half maximum of the spectral features. Thermal quenching of the fluorescent yield is discussed and calculated in a less accurate way, but anyway showing good agreement with experiment.PACS numbers: 78.20.Bh Fluorescence is generally associated to transitions of a local electronic orbital causing a significant structural variation, and hence a strong perturbation of the dynamics of nuclear degrees of freedom. The absent, or very weak [1], zero-phonon line in the observed spectra proves in empirical way that few-phonon processes are infrequent. The wide frequency spectra of the exchanged photons, the large Stokes shifts and peak asymmetries, and the marked dependence of the spectral features on the local and long-range properties of the hosting medium, have all them a common explanation: the large amount of energy spent in exciting acoustic traveling waves in the medium hosting the fluorescent molecule [2,3]. From a thermodynamic standpoint, the electronic and electromagnetic radiation fields are two weakly coupled systems going through a transformation between two well defined states, in thermal equilibrium with the energy reservoir constituted by the acoustic vibrational modes of the extended material medium. By the entropy law, the thermal bath always takes a positive amount of energy in the average. In photon absorption processes the radiation field statistically provides the energy delivered to the thermal bath, and the electron field does in the emission events. Then the Stokes shift is a direct consequence of the second law of thermodynamics. Peak asymmetries have a similar general explanation, since photons carrying an energy excess, or defect, are more probable in absorption, or emission, processes.The technology of fluorescence has advanced at an accelerating pace in a variety of applications [4][5][6]. Many of them follow from the sensitivity of the optical properties of the fluorophores to the physical attributes of the embedding medium [7][8][9][10][11][12][13]. Despite these advances, there are still some aspects which deserve deeper under- * Electronic address: mlagos@utalca.cl † Electronic address: raparede@utalca.cl ‡ Electronic address: ceretamal@utalca.cl standing. Recent papers report a theoretical framework able to reproduce with high numerical precision the temperature dependent lineshapes [2] and quenching [3] of the fluorescent spectra of molecules in a condensed environment. The purpose of this comm...

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Potential problems in collection and data processing of luminescence signals

Wang

Townsend

2013

Journal of Luminescence

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Line shapes of narrow optical bands: Infrared absorption byUcenters and heavier impurities in alkali halides

Cited by 6 publications

References 13 publications

Fourier Transform Spectrometry with Fourier Analysis of the Interferogram as Just an Optional Tool

Fourier Transform Spectrometry with Fourier Analysis of the Interferogram as Just an Optional Tool

High precision energy measurements from the analysis of wide spectral features. Application to the fluorescence of YAG:Ce 3+

Potential problems in collection and data processing of luminescence signals

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