Time-resolved Fluorescence Line Narrowing Research Articles

A site-selective fluorescence spectroscopy study of the crystal phases of KY3F10: Leveraging the optical response of Eu3+ ions

The present work deals with the investigation of the site-selective symmetries in Eu3+-doped KY3F10 with different crystal phases. Employing time-resolved fluorescence line-narrowing (TRFLN), a study of the luminescent response of the dopant is reported in samples presenting a single δ-phase, a single α-phase, and a mixture of both δ and α. A new, simple, very low time-consuming and high-yield method was developed to obtain nanospheres of the δ-phase. For both crystal phases, the main site symmetry is spectrally corroborated with that expected by the crystallographic substitution position (C2v in δ, and C4v in α). In addition, the accuracy of the measurements also unveils the presence of significantly distorted Eu3+ ions in the surface of the nanoparticles in all the samples studied, a spectral behavior commonly found in glassy systems. All these findings contribute to the proper understanding of the optical response of luminescent dopants in this and related types of complex fluorides. It is worth highlighting the fact that the huge potential of the unexplored δ-phase is demonstrated, since the site-selective emission of the Eu3+-doped δ-phase is up to 20 times more intense than that of the α-phase.

Time-resolved fluorescence line-narrowing of Eu^3+ in biocompatible eutectic glass-ceramics

The spectroscopic properties of Eu(3+) in biocompatible glass and glass-ceramic eutectic rods of composition 0.8CaSiO(3)-0.2Ca(3)(PO(4))(2) doped with 0.5 wt% of Eu(2)O(3) are investigated to explore their potential applications as optical probes. The samples were obtained by the laser floating zone technique. Depending on the growth rate, they exhibit three (two crystalline and one amorphous) or two (one crystalline and one amorphous) phases. The crystalline phases correspond to Ca(2)SiO(4) and apatite-like structures. At high growth rates the system presents an amorphous arrangement which gives a glass phase. The results of time-resolved fluorescence line narrowing spectroscopy obtained under excitation within the inhomogeneous broadened (7)F(0)→(5)D(0) absorption band allow to isolate the emission from Eu(3+) ions in the crystalline and amorphous environments and to accurately correlate the spectroscopic properties with the microstructure of these eutectics.

Laser spectroscopy of Nd 3+ ions in glasses with the 0.8CaSiO 3–0.2Ca 3(PO 4) 2 eutectic composition

In this work we report the study of site-selective laser spectroscopy of Nd 3+ ions in glasses with the 0.8CaSiO 3–0.2Ca 3(PO 4) 2 eutectic composition together with a dynamic study of energy transfer among Nd 3+ ions by using time-resolved fluorescence line narrowing (TRFLN) spectroscopy. The spectral features of the time-resolved fluorescence line narrowed 4 F 3 / 2 → 4 I 9 / 2 emission spectra obtained under resonant excitation reveal the existence of spectral migration of excitation among the Nd 3+ ions. The analysis of the time evolution of the 4 F 3 / 2 → 4 I 9 / 2 narrowed emission shows that the electronic mechanism responsible for the ion–ion interaction can be identified as a dipole–dipole energy transfer process.

Temperature and pressure dependence of the homogeneous width of 7F 0– 5D 0 electronic transition in Sm 2+-doped sodium borate glass

The homogeneous width Γ h of 7F 0↔ 5D 0 transition in Sm 2+ ions doped into sodium borate glass was determined at T=5–293 K under P=1 bar and at T=5, 80 and 120 K under various P up to 8 kbar. The line width Γ h was obtained from spectral hole burning (SHB) and time-resolved resonant fluorescence line narrowing (FLN) experiments. It was found that at P=1 bar the T-dependence of Γ h changes from Γ h( T)∝ T 2 (quadratic) for T<20 K to Γ h( T)∝ T (linear) for T>20 K. Under pressure, Γ h grows slightly at all three T values studied (at 80 K by 1.2%/kbar and at 120 K by 1.6%/kbar in the range 0–8 kbar). Possible mechanisms to explain the observed T- and P-dependences of Γ h are briefly discussed.

Energy transfer studies in Eu3+-doped lead–niobium–germanate glasses

The spectral migration of energy among Eu 3+ ions in lead-niobium-germanate glass (60GeO 2 -25PbO-15Nb205) with different Eu 3+ concentrations (0.5, 1, 3, and 5 mol%) has been investigated at low temperature by using time-resolved fluorescence line narrowing (TRFLN) spectroscopy. The spectral features of the time-resolved fluorescence line-narrowed 5 D 0 → 7 F 0 emission spectra under resonant excitation at different wavelengths along the 7 F 0 → 5 D 0 transition as a function of time, excitation wavelength, and concentration reveal the existence of energy migration between discrete regions of the inhomogeneous broadened spectral profile. The analysis of the time evolution of the 5 D 0 → 7 F 0 emission shows that the electronic mechanism responsible for the ion-ion interaction can be identified as a dipole-dipole energy transfer process.

Time-resolved fluorescence line narrowing spectroscopy and fluorescence quenching in Nd3+-doped fluoroarsenate glasses

Abstract The spectral migration of energy among the Nd 3+ ions in fluoroarsenate glasses of the Na 4 As 2 O 7 , BaF 2 , YF 3 system with different Nd 3+ concentrations (0.5, 2, 3, 4, and 5 mol%) has been investigated by using time-resolved fluorescence line narrowing (TRFLN) spectroscopy. The features of the time-resolved fluorescence line narrowing 4 F 3/2 → 4 I 9/2 emission spectra obtained under resonant excitation at different wavelengths along the 4 I 9/2 → 4 F 3/2 transition as a function of Nd 3+ concentration reveal the existence of energy migration between discrete regions of the inhomogeneously broadened spectral profile. The analysis of the time evolution of the 4 F 3/2 → 4 I 9/2 narrowed emission shows that the electronic mechanism responsible for the ion–ion interaction can be identified as a dipole–dipole energy transfer process. From the thermal behavior of lifetimes of the 4 F 3/2 state a T 3 dependence for the non-radiative Nd–Nd relaxation processes has been found in the 10–80 K temperature range for Nd 3+ concentrations higher than 0.5 mol% which is in agreement with a two-site non-resonant process.

Energy transfer between Eu 3+ ions in sol–gel derived silica glasses

Time-resolved fluorescence line narrowing technique has been used to analyse the evolution of the 5D 0→ 7F 0 emission of Eu 3+ ions in sol–gel derived silica glasses. These samples were doped with 2.5 mol% of Eu 3+ and heat treated at different temperatures. Background fluorescence, coming from Eu 3+ ions excited by energy transfer processes, was observed in these experiments. Using a previously proposed equation model, a study of the multipole character of the interaction between Eu 3+ ions was performed. The annealing process carried out in the samples causes important changes in the efficiency of energy transfer process and in its multipole character, varying from S=6 (in a sample treated at 400°C) to S=10 (in a sample treated at 600°C), indicating that the environment of Eu 3+ ions has been modified.

Fluorescence line narrowing study of Cr [formula omitted] ions in cordierite glass nucleating MgAl [formula omitted]O [formula omitted] nanocrystals

The luminescence of Cr 3+ ions in cordierite glass nucleating MgAl 2 O 4 nanocrystallites has been investigated. The time resolved fluorescence line narrowing measurements and the temperature dependence of the homogeneous line width show that most Cr 3+ ions are inside the nanocrystallites. Cr 3+ ions occupy non-equivalent crystal sites, due to the Mg 2+ –Al 3+ inversion effect. The values of the homogeneous line width compare well with those of previous studies in crystals. No surface effect has been observed due to the large size of the crystals.

Energy transfer between Eu3+ ions in calcium diborate glasses

The evolution of the 5D0 7F0 emission of Eu3+ ions in calcium diborate glasses has been analysed using time resolved fluorescence line narrowing measurements in order to give a complete view of the energy transfer processes between these ions. At low concentration (2.5 mol% of Eu2O3) and exciting within the high energy side of the inhomogeneous 7F0 5D0 absorption band, the luminescence spectrum mainly consists of a narrow resonant peak that repeats the exciting profile, indicating that the migration processes between Eu3+ ions within the 5D0 level is not important. However, at higher concentrations (5 to 11.5 mol% of Eu2O3) the luminescence spectrum contains not only a narrow emission but also a broad band due to ions excited by energy transfer (background fluorescence), which for long times well reproduces the inhomogeneous profile. The temporal evolution of the narrow band fluorescence and the shape of the background fluorescence have been analysed using a previously proposed model. The purpose is to understand the dynamics involved in the energy transfer processes caused by the interaction between Eu3+ ions and the implications in their luminescence. A very good agreement with the experimental results is found taking into account an energy dependent quadrupole-quadrupole (S = 10) non-radiative energy transfer process assisted by a phonon from Eu3+ ions at high crystal field sites to ions at low crystal field sites. The temperature dependence of the energy transfer processes is analysed in the range from 13 to 60 K.

Fluorescence line Narrowing Spectroscopy of Germanate Glasses Doped with Eu3+

ABSTRACTIn the present paper we report on time-resolved resonant and non-resonant fluorescence line narrowing measurements on a lead germanate glass doped with Eu3+. Site-selective decay curves were measured at low temperature. The results show that energy transfer processes between Eu3+, ions in different sites are not efficient at the doping level under investigation (I mol% Eu2O3). The homogeneous linewidth of the 5D0→47F0transition was measured at room temperature as a function of the excitation energy within the inhomogeneous profile. The linear dependence of the homogeneous linewidth on the excitation energy is discussed.

Excited state absorption and fluorescence line narrowing studies of Cm3+ in LuPO4

Laser selective excitation, fluorescence line narrowing, and excited state absorption techniques have been used to investigate the electronic-energy-level structure of the 5f7 ion Cm3+ in the host crystal LuPO4. Crystal-field levels have been determined up to 35 700 cm−1 for the principal D2d symmetry site. Eighty levels have been assigned and fitted to a parametric Hamiltonian with an rms deviation of 28.4 cm−1. Inhomogeneous broadening of the electronic transitions and the small 9.5 cm−1 splitting of the nominally 8S7/2 ground multiplet are responsible for satellite lines reported previously. Time resolved fluorescence line narrowing was used to observe energy transfer between different subsites of the intrinsic Cm3+ center. It was found that electric-dipole interactions mediate this energy transfer.

Luminescence of the Cr3+ ion in sodium beta - and beta "-alumina: Site selection by time-resolved fluorescence line narrowing.

Fluorescence of ${\mathrm{Cr}}^{3+}$ ions in the two different octahedral sites of the spinel block of \ensuremath{\beta}- and \ensuremath{\beta}''-alumina have been measured by time-resolved fluorescence line-narrowing spectroscopy. For the excitation either a pulsed or a chopped cw-dye laser was used. Lifetimes and splittings of the ground state ${(}^{4}$${\mathit{A}}_{2}$) and of the $^{2}$E state have been measured by tuning the excitation energy within the inhomogeneous profile of the ${\mathit{R}}_{1}$ and ${\mathit{R}}_{2}$ lines of the split $^{2}$E${\mathrm{\ensuremath{-}}}^{4}$${\mathit{A}}_{2}$ transition. In sodium \ensuremath{\beta}''-alumina, we have isolated several inequivalent emitting centers, which are related to different configurations of the stabilizing ${\mathrm{Mg}}^{2+}$ ions.

The fluorescence line narrowing of Sm3+ in ZBLAN fluoride glass

The fluorescence line narrowing (FLN) and time resolved fluorescence line narrowing (TRFLN) of Sm 3+ ions in ZBLAN fluoride glass have been investigated. The fluorescence transitions 4 G 5 2 − 6 H 5 2 and 4 G 5 2 − 6 H 7 2 were detected as the wavelength of the exciting light was varied. The homogeneous broadened luminescence of 4 G 5 2 − 6 H 5 2 by resonant excitation has been recorded at temperatures as low as 100 K; a 2.5 cm −1 linewidth was measured at this temperature, and the delay-time dependence and temperature dependence of the spectral width were studied.

Resonant fluorescence line narrowing in La1-xNdxP5O14 glass

The absorption spectra and fluorescence spectra of La1-xNdxP5O14 (LNPP) glass were studied. The fluorescence from the level of interest 4F3/2 (1) state shows an exponential decay and linear concentration quenching. Time resolved fluorescence line narrowing was observed for LNPP glass with different x values. For high x value LNPP glass, energy transfer between Nd3+ ions intraline was observed at low temperature.

Fluorescence quenching in Sm 3+ doped KYP 4O 12 crystals

The nature and the magnitude of quenching of fluorescence from the 4G 5 2 excited state of Sm 3+ in KYP 4O 12 have been investigated. Low-temperature excitation spectra of the 4G 5 2 state reveal the complex additional line structure associated with the presence of Sm 3+ ion pairs. The measured values of cross-relaxation rates for various pairs together with the sequence of ion pair separations in tetrametaphosphate lattice indicate that the electric dipole-quadrupole interaction is responsible for the cross-relaxation process. The inhomogeneous line broadening in the investigated system is studied using time-resolved fluorescence line narrowing. Between 4.4 and 35 K no spectral diffusion across the inhomogeneously broadened line is observed and 4G 5 2 fluorescence decay is analyzed within the framework of both the Inokuti-Hirayama and the discrete host crystal models. Shortening of the 4G 5 2 decay at high excitation density has been observed and is discussed in terms of cooperative ion interaction.

Chromium-gallium complexes in Al 2O 3 I. luminescence

The shift and broadening of the R lines in gallium-doped ruby are studied as a function of the gallium impurity content (< 2%). A great number of well-resolved emission lines are assigned to gallium-chromium pairs; their first and second excited states are identified by excitation spectroscopy. Weaker lines are assigned to triads formed by one chromium ion and two gallium ions. For most of these triads the shifts of the R lines due to each of the two gallium ions add linearly. A triad formed by two chromium ions (4th NN) and one gallium ion (1st NN to one chromium ion) is also identified and studied. Time-resolved fluorescence line narrowing measurements allow the determination of the energy level scheme of a pair of loosely bound chromium ions.

Time Resolved Fluorescence Line Narrowing in Ytterbium-Doped Inorganic Glasses

ABSTRACTWe have used time resolved fluorescence line narrowing to study optical dephasing and energy transfer among Yb3+ ions doped in inorganic glasses. We observe for the first time in any rare earth doped glass system a change in the power of the temperature dependence of the homogeneous linewidth of the 2F5/2(1)-2F7/2(1) transition of Yb, 3+ as well as an efficient one-phonon assisted energy transfer process occuring among Yb3+ ions at higher concentration due to a quadrupole-quadrupole coupling of the ions. In this paper we review past studies in rare earth doped gla s systems of these topics and compare them to our observations of Yb3+ in silicate and phesphate glasses.

Fluorescence quenching and spectral diffusion inLa1−xP5O14:Ndx3+

Donor-donor and donor-acceptor spectral dynamics are studied in the laser material ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{P}}_{5}{\mathrm{O}}_{14}$:$\mathrm{Nd}_{x}^{}{}_{}{}^{3+}$ using time-resolved fluorescence line narrowing. Direct excitation in the $^{4}F_{\frac{3}{2}}(1)$ state in $x=0.2,0.75, \mathrm{and} 1.0$ samples shows exponential fluorescence decay and linear concentration quenching of the line-narrowed component between 4.5 and 20 K. No spectral diffusion across the inhomogeneously broadened line is observed in this temperature region. This unusual exponential decay and linear quenching in the absence of fast donor-donor transfer is explained with a generalized Inokuti-Hirayama model. An onset of spectral migration is observed in $x=0.2 \mathrm{and} 0.75$ at 20 K, indicating the presence of phonon-assisted energy transfer. The temperature dependence of the phonon-assisted donor-donor transfer rate is measured for $x=0.2$ between 17 and 24 K. This temperature dependence identifies the one-site resonant process, with an activation energy corresponding to the $^{4}I_{\frac{9}{2}}(2)\ensuremath{-}^{4}I_{\frac{9}{2}}(1)$ splitting, as the probable donor-donor interaction mechanism. The low-temperature results and the spectral diffusion measurements are described consistently in the studied temperature range by phonon-assisted energy transfer models, in which the donor excitation is transferred between single ions in an incoherent manner.

Time resolved fluorescence line narrowing of ions in solids

Recent applications of tunable dye laser spectroscopic techniques to the spectroscopy of ions in solids are reviewed. Emphasis is placed on advances in the interpretation of time resolved fluorescence line narrowing (FLN) spectra of ion in insulators as they apply to the dynamics of optically excited states of these ions.

Temperature, temporal and concentration dependence of the laser-narrowed 5D 0 → 7F 0 fluorescence limeshape of Eu 3+ in glasses

Time-resolved laser-induced fluorescence line-narrowing -techniques employing gated vidicon detection have been used to study the homogeneous resonance fluorescence linewidth of the 5D 0 → 7F 0 transition of Eu 3+ at low concentration in Inorganic glasses. The linewidth is shown to be determined by the rate of phase-interrupting, two-phonon Raman scattering processes. The efficiency of these processes is found to be sensitive to the strength of the crystal field of the particular site in which a Eu 3+ ion sits. At higher concentrations, the laser-narrowed fluorescence lineshape becomes time-dependent, due to site-to-site phonon-assisted energy transfer processes. Its Intensity is found to decrease (retaining the same value for its half-width) while a growth of the inhomogeneous line profile is observed as time elapses after the initial laser excitation. From this behavior, the transfer rate is determined and studied as a function of concentration, temperature, and wavelength of excitation. We conclude that the electronic coupling mechanism is dipolar in nature and the phonon assistance occurs via a two-phonon Raman process with one phonon scattered at each of the coupled sites.