Infrared Fluorescence Spectra Research Articles

Investigation of growth and polarized spectra of Ho3+ ions heavily doped BaY2F8 crystal

A BaY2F8 (BYF) single crystal heavily doped with Ho3+ ion was grown successfully using the Czochralski (Cz) method. The infrared fluorescence spectra (2–4 μm) and fluorescence lifetime at 3.9 μm were investigated. The detailed polarization absorption properties of Ho:BYF, especially the absorption spectrum in 850–950 nm range, were reported for the first time. The maximum absorption cross-section was at 888.15 nm, σabs = 1.26✕10−21 cm2 (E//c). In comparison, the peak positions of the absorption cross sections in the other two polarization directions were at 885.80 nm and 890.45 nm, respectively, indicating that incident light's polarization direction greatly influences absorption. The spectroscopic parameters were calculated based on the Judd–Ofelt theory.

Assessing the effect of soil to water ratios and sampling strategies on the prediction of EC and pH using pXRF and Vis-NIR spectra

Soil electrical conductivity (EC) and pH play a critical role in managing agricultural productivity. We investigated the effect of soil to water ratios (1:1, 1:2.5, 1:5) and sampling strategies (surface, profile wall, and surface + profile wall) on prediction accuracy using individual and combined visible near infrared (Vis-NIR) and portable X-ray fluorescence (pXRF) spectra with machine learning algorithms for EC and pH. In total, 200 soil samples were collected from the soil surface (100 soil samples) and profile wall (100 soil samples) in pasture lands in Eskisehir, Türkiye. The soil samples were analyzed by considering soil to water ratios (1:1, 1:2.5, 1:5) for EC and pH and scanned by Vis-NIR (350–2500 nm) and pXRF (0–45 keV). In total 54 different predictor models were tested to achieve the highest prediction accuracy for both EC and pH. The seven machine learning regressions (elastic net, k-nearest neighbors, lasso, partial least squares, random forest, ridge, and support vector machine-linear) were applied in modeling with calibration (70 % soil samples) and validation (30 % soil samples) datasets for each model. The results suggested that the EC1:2.5 and EC1:5 ratios had relatively higher prediction accuracy (r = 0.95, R2 = 0.93, RMSE = 0.58, MAE = 0.46, RPD = 3.57, and RPIQ = 5.33) using Vis-NIR spectra with partial least squares and support vector machine-linear models in profile wall compared to other sampling strategies and EC1:1 ratio. The pH1:2.5 ratio had relatively higher prediction accuracy (r = 0.90, R2 = 0.81, RMSE = 0.07, MAE = 0.06, RPD = 2.49, and RPIQ = 3.71) using Vis-NIR spectra with random forest model in profile wall compared to other sampling strategies and pH1:1 and pH1:5 ratios. In addition, combined Vis-NIR and pXRF spectra had no improvement in prediction accuracy. Finally, it can be concluded that the prediction accuracy is affected by soil to water ratios and sampling strategies. Individual Vis-NIR spectra can reach the highest prediction accuracy for EC and pH compared to combined pXRF and Vis-NIR spectra.

Enhanced mid-infrared emission of Pr3+ ions in solids through a "3-for-1" excitation process - quantified.

Evidence is presented that a "three-for-one" process based on two cross-relaxations between Pr3+ ions efficiently populates the mid-infrared-emitting 3H5 manifold in a Pr3+-doped low-maximum-phonon-energy host. The concentration dependence of infrared fluorescence spectra and lifetimes of polycrystalline Pr:KPb2Cl5 initially excited to the 3F3,4 manifolds indicate that the 3500-5500-nm fluorescence becomes strongly favored over shorter-wavelength infrared emission bands in the higher-concentration sample. The strong concentration dependence of the 3F3 and 3H6 manifold lifetimes suggests that both of these decay by cross-relaxation processes, resulting in more than one ion excited to 3H5 for each ion initially excited to 3F3. Indeed, modeling and accounting for all possible decay paths indicate that, on average, about 2.3 ions are excited to 3H5 for each initially-excited ion. This confirms that the three-for-one excitation process must occur and contribute significantly to the total excitation efficiency. These results indicate that the two distinct cross-relaxation processes observed between Pr ions result in substantially higher excitation quantum efficiency, 230%, than any ever reported in rare-earth doped materials.

Fluorescence-based quantitative characterization of structural phase transitions in Li+/Er3+:BaTiO3 ferroelectric ceramics

We propose a method to quantitatively characterize the fine phase transition processes of Li+/Er3+:BaTiO3 (BLET) ferroelectric materials by observing fluorescence wavelength shift. A lithium and erbium co-doped barium titanate ferroelectric ceramic was fabricated and the down-conversion infrared fluorescence spectra of the transition 4I13/2 → 4I15/2 were measured as a function of temperature. The three structural phase transition processes, namely rhombohedral–orthorhombic, orthorhombic–tetragonal, and tetragonal–cubic transformations, determined by X-ray diffraction results are accompanied by corresponding changes in the position of the fluorescence peaks, yielding an exact consistency. This contactless, non-destructive and spatially-resolved fluorescence method provides a localized quantitative analysis for the phase transition processes of BLET ceramics. As this method is based on the fluorescence peak wavelength dependence on the crystal environment, it may potentially be used to characterize the phase transitions in other ferroelectric materials.

Spectroscopic evidence of cooperative (entangled) quantum states of Nd3+ ion pairs in Nd3+: LaF3 crystal

We demonstrated the existence of entangled 4I9/2(1) x 4G5/2(1) quantum state in a pair of Nd3+ ions due to strong resonance quadrupole – quadrupole interaction between the ions. In doing so, we used narrow line (0.05 Å) tunable pulsed dye laser excitation of a 1% Nd3+: LaF3 crystal at liquid helium temperatures at the 4I9/2(1) → 4G5/2(1) transition and measured the site-selective near infrared (NIR) fluorescence spectra of different optical centers (OCs) at the 4F3/2(1) → 4I9/2(1) transition of Nd3+ with high spectral resolution (0.1 Å); the NIR fluorescence excitation spectra at the 4I9/2(1) → 4G5/2(1) transition (0.05 Å); and by varying the excitation and detection wavelengths we measured the IR fluorescence kinetics of the selected type of OCs. As a result, we observed inhomogeneous splitting within 30 cm−1 of wavenumbers for the fluorescence spectra at the 4F3/2(1) → 4I9/2(1) transition, manifested in the presence of numerous narrow inhomogeneously broadened spectral lines of different OCs. We have attributed each spectral line to a different single-site, pair, triple, or quad optical centers via analysis of the 4F3/2(1) metastable level fluorescence kinetics decay times. Each type of OCs demonstrates its own specific IR fluorescence excitation spectrum at the 4I9/2(1) → 4G5/2(1) transition detected in a 1%Nd3+: LaF3 crystal at 1.6 K. One of the spectral lines of the pair centers (with the frequency 17313.3 cm−1) exhibited the fine splitting with the value of 0.2 cm−1. The shape and the value of fine splitting are explained theoretically assuming that this line corresponds to the excitation of the entangled the 4I9/2(1) x 4G5/2(1) quantum state of the pair of Nd3+ ions located at short distance, R ~ 4.1 Å.

The mid-infrared emission properties and energy transfer of Tm3+ /Er3+ co-doped tellurite glass pumped by 808/980nm laser diodes

The spectral performance of the Tm3+/Er3+ co-doped tellurite glass under the pump at 808/980 nm and the energy transfer process between Tm3+ and Er3+ were mainly studied. The mid infrared fluorescence spectra showed that when the concentration of doped Er3+ ion was 0.5mol%, the fluorescence intensity of 1.8 μm and 2.7 μm reached the peak. While at the pump of 980 nm, the maximum occurred in 1mol% of Er3+ ions. Under 808/980 nm pumping system, different energy transfer mechanisms between Tm3+ and Er3+ ions were accordingly proposed. The maximum emission cross section of 0.5 Tm3+/0.5Er3+ codoped sample can reach 4.68 × 10−21 cm2 at 1886 nm. When P was 0.4, the gain of Tm3+:3F4→3H6 at 1852–2100 nm started to be positive while its maximum gain coefficient was 0.91 cm−1, and its central wavelength was 1887 nm. Therefore, the large emission cross section and the high gain are conducive to the Tm3+/Er3+ co-doped tellurite glass to obtain low threshold value and high gain of the 2 μm laser output.

Dependence of the hydration status of bacterial light-harvesting complex 2 on polyol cosolvents.

Low molecular weight (MW) polyols are organic osmolytes influencing protein structure and activity. We have intended to investigate the effects of low MW polyols on the optical and the excited-state properties of the light-harvesting complex 2 (LH2) isolated from the photosynthetic bacterium Thermochromatium (Tch.) tepidum, a thermophile growing at ∼50 °C. Steady state spectroscopy demonstrated that, on increasing glycerol or sorbitol fractions up to 60% (polyol/water, v/v), the visible absorption of carotenoids (Crts) remained unchanged, while the near infrared Qy absorption of bacteriochlorophyll a (BChl) at 800 nm (B800) and 850 nm (B850) varied slightly. Further increasing the fraction of glycerol (but not sorbitol) to 80% (v/v) induced distinct changes of the near infrared absorption and fluorescence spectra. Transient absorption spectroscopy revealed that, following the fast processes of BChl-to-Crt triplet energy transfer, rather weak Qy signals of B800 and B850 remained and evolved in phase with the kinetics of triplet excited state Crt (3Crt*), which are attributed to the Qy band shift as a result of 3Crt*-BChl interaction. The steady state and the transient spectral responses of the Qy bands are found to correlate intimately with the water activity varying against polyol MW and mixing ratio, which are rationalized by the change of the hydration status of the C- and N-termini of LH2. Our results suggest that, with reference to the mesophilic purple bacterium Rhodobacter sphaeroides 2.4.1, Tch. tepidum adopts substantially more robust LH2 hydration against the osmotic effects from the low MW polyols.

Energy transfer and enhanced 1.53 µm band signal gain in Er3+/Ce3+ codoped tellurite glass fiber

A detailed study of the energy transfer between Er3+ and Ce3+ ions and its enhanced effects on the 1.53µm band signal gain in Er3+/Ce3+ codoped tellurite glass fiber under the excitation of 980nm is reported. The absorption spectra, visible upconversion spectra, infrared fluorescence spectra of Er3+ doped and Er3+/Ce3+ codoped glass samples were measured, and the 1.53µm band signal gain of Er3+ doped and Er3+/Ce3+ codoped glass fiber was calculated based on the rate and power propagation equations. Codoping Ce3+ with Er3+ ions can significantly suppress the visible upconversion emission and meanwhile improves the 1.53µm band fluorescence, and an increment of about 6.4dB signal gain at 1532nm was found in a 40cm glass fiber with 150mW pumping power at 980nm, which is ascribed to the energy transfer between Er3+ and Ce3+ ions. The quantitative analysis showed that the energy transfer between Er3+ and Ce3+ ions is a one phonon and two phonon-assisted energy transfer process. The results indicated that Er3+/Ce3+ codoping is a suitable scheme for low phonon energy tellurite glass fiber applied for broadband and high gain EDFA.

The spectral and catalytic studies of chlorophylls and pheophytins in mimetic biotransformation of α-pinene

Natural porphyrin pigments isolated from spinach in the form of a crude extract, chlorophyll a, chlorophyll b, pheophytin a and pheophytin b were studied as potential catalysts for the biomimetic transformation of α-pinene to trans-pinocarveol, pinocarvone and myrtenal. The reaction of monoterpene oxidation was performed in an organic solution under visible light irradiation. Significant changes in the distribution of the products were achieved using β-pinene as the substrate. The pheophytins showed the highest catalytic efficiency among the photocatalysts examined. The photographic visualization of α-pinene oxidation course at the beginning of the reaction, after 4 and 24 h exposure to light showed a distinct shift in the colour excited catalysts. This may indicate a change in their structure leading to their degradation. The absorbance and fluorescence spectra revealed that pheophytins are significantly stable photocatalysts in comparison to both chlorophylls. Pheophytin b displayed the highest stability in the biotransformation, whereas the highest rate of photodecomposition was proved for chlorophyll b under the reaction condition. Differences were noticed in the behaviour of the chlorophylls in the photodegradation process. From the changes in the intensity of the singlet oxygen band on infrared fluorescence spectra of pigments upon pinene addition, and from the reactivity experiments with radicals scavengers, it can be deduced that the biotransformation of pinene by chlorophylls and pheophytins proceeds by common oxygenation mechanism involving singlet oxygen and free radicals.

Infrared quantum cutting conversion luminescence of Tb(0.7)Yb(3):FOV

The infrared quantum cutting of oxyfluoride nanophase vitroceramics Tb(0.7)Yb(3):FOV has been studied in the present paper. The actual quantum cutting efficiency formula calculated from integral fluorescence intensity is extended to the case of Tb(0.7)Yb(3):FOV. The visible and the infrared fluorescence spectra and their integral fluorescence intensities are measured from static fluorescence experiment. Lifetime curve is measured from dynamic fluorescence experiment. It is found that the total actual quantum cutting efficiency η of the excited 5D4 level is about 93.7%, and that of excited (5D3, 5G6) levels is 93.5%. It is also found that the total theoretical quantum cutting efficiency upper limit ηx%Yb of the 485.5 nm excited 5D4 level is about 121.7%, and that of 378.5 nm excited (5D3, 5G6) levels is 137.2%.

Optical absorption and near infrared emission properties of Nd 3+ ions in alkali lead tellurofluoroborate glasses

Nd 3+ doped H 3BO 3–PbO–TeO 2–RF (R = Li, Na and K) glasses were prepared through melt quenching technique. Optical absorption and near infrared (NIR) fluorescence spectra were recorded at room temperature. The spectral intensities were analyzed in terms of the Judd–Ofelt (J–O) parameters ( Ω λ = 2, 4, 6). The covalency effect of Nd–O bond on the J–O parameters was estimated from the relative absorbance ratio (R) between 4I 9/2 → 4F 7/2 and 4I 9/2 → 4S 3/2 transitions. The effect of Nd–O covalency on the Ω 4 and Ω 6 intensity parameters as well as on the spontaneous emission probabilities ( A R) was discussed. Lomheim and Shazer hybrid method was applied to determine the fluorescence branching ratios ( β R) of each emission transition from the 4F 3/2 metastable level to its lower lying levels. The evaluated total radiative transition probabilities ( A T), stimulated emission cross-sections ( σ e) and gain bandwidth parameters ( σ e × Δ λ P) were compared with the earlier reports.

Structural and optical investigations of Nd-doped fluorozirconate-based glass ceramics for enhanced upconverted fluorescence

We found enhanced upconverted fluorescence in Nd3+-doped fluorozirconate glasses which were additionally doped with chlorine ions. Upon annealing between 240 and 290°C, hexagonal phase BaCl2 nanocrystals between 20 and 180nm in diameter were formed in the glass. During the thermal processing, some of the Nd3+ ions enter the nanocrystals leading to additional splitting of the infrared fluorescence spectra and to increased upconverted fluorescence intensities. The optimum value was found for the 270°C sample where the upconverted fluorescence intensity is approximately a factor of 60 stronger than the one found for the as-made glass.

Preparation and characterization of BaLiF 3:Er 3+ nanoparticles by the hydrothermal microemulsion synthesized method

Nanoparticles of BaLiF 3:Er 3+ were prepared from the quaternary microemulsions of Cetyltrim-Enthyl Ammonium Bromide (CTAB), n-butanol, n-octane, and water, using the hydrothermal-microemulsion technique. The complex fluorides were characterized by means of X-ray power diffraction, Environmental Scanning Electron Microscopy (ESEM), and fluorescence spectra. The positions and intensities of the peaks in the XRD pattern of the final products indicate the formation of BaLiF 3:Er 3+. No other peaks or impurities were detected. The average size of the nanoparticles, calculated with the Debye-Scherrer equation was 98.45 nm, which was in agreement with the result of ESEM. The infrared fluorescence spectra consisted of four peaks with a predominant peak located at 1540 nm.

Polarized spectroscopic properties of Nd 3+-doped KGd(WO 4) 2 single crystal

The polarized absorption spectra, infrared fluorescence spectra, upconversion visible fluorescence spectra, and fluorescence decay curve of orientated Nd 3+:KGd(WO 4) 2 crystal were measured at room-temperature. Some important spectroscopic parameters were investigated in detail in the framework of the Judd–Ofelt theory and the Fuchtbauer–Ladenburg formula. The effect of the crystal structure on the spectroscopic properties of the Nd 3+ ions was analyzed. The relation among the spectroscopic parameters and the laser performances of the Nd 3+:KGd(WO 4) 2 crystal was discussed.

Self-assembled monolayer of light-harvesting core complexes of photosynthetic bacteria on an amino-terminated ITO electrode.

Light-harvesting antenna core (LH1-RC) complexes isolated from Rhodospirillum rubrum and Rhodopseudomonas palustris were successfully self-assembled on an ITO electrode modified with 3-aminopropyltriethoxysilane. Near infra-red (NIR) absorption, fluorescence, and IR spectra of these LH1-RC complexes indicated that these LH1-RC complexes on the electrode were stable on the electrode. An efficient energy transfer and photocurrent responses of these LH1-RC complexes on the electrode were observed upon illumination of the LH1 complex at 880 nm.

Thermal analysis and optical properties of Yb^3+/Er^3+-codoped oxyfluoride germanate glasses

Yb3+/Er3+-codoped Na2O–Al2O3–GeO2–PbO–PbF2 glasses that are suitable for use in fiber lasers, amplifiers, and waveguide devices have been fabricated and characterized. The density, refractive indices, optical absorptions, Judd–Ofelt parameters, and spontaneous-transition probabilities of the glasses have been measured and calculated. Intense and broad 1.53-μm infrared fluorescence and visible upconversion luminescence were observed under 976-nm diode laser excitation. For the 1.53-μm emission band, the full widths at the half-maximum increase and the peak wavelengths are blueshifted with an increase of PbF2. The stimulated-emission cross sections were calculated from the measured-absorption cross section according to the McCumber theory. The monotonically reduced emission cross section arises from the decreased refractive indices of glasses and the increased linewidth of the infrared fluorescence spectrum. For the upconversion emissions centered at 524, 547, and 660 nm, the emission intensity changes remarkably with PbF2 contents from 0 to 15 mol.%. The quadratic dependence of the green and red emissions on excitation power indicates that a two-photon absorption process occurs under the 976-nm excitation. The relatively long lifetimes of the Er3+ 4S3/2 and 4F9/2 levels for the NAGF3 glass gives rise to a much more intense upconversion emission.

Optical properties of tsavorite Ca3Al2(SiO4)3:Cr3+, V3+ from Kenya

Previously, a relatively large splitting of the 2Eg state of Cr3+ in grossular Ca3Al2[SiO4]3 has been reported [M. Czaja and Z. Mazurak, Opt. Mater 3 (1994) 95]. The absorption and luminescence spectra of crystals containing Cr3+ and V3+in grossular Ca3Al2(SiO4)3 garnets (variety tsavorite) have been studied for the first time. From these spectra measured at room and liquid helium temperatures we determined energies of R2, R1, and 4T2g levels of Cr3+. The lifetimes and splitting of the 2Eg state have been measured by tuning the excitation energy within the inhomogeneous profile of the R1 and R2 lines of the split 2Eg → 4A2g transition. To account for the thermal quenching of the R-lines, it is necessary to recognize that the two components of the doublet may have remarkably different radiative lifetimes (7500 and 2500 μs). These lifetimes were obtained from low temperature decay and from the temperature dependence of the intensity ratio of the R2, R1 components. These separate lifetimes as well as the lifetime of the 4T2g state were then set to fit the temperature dependence of the joint effective lifetime. The optical fluorescence of a V3+ dopant is characterized by the broad band infrared fluorescence spectrum associated with short decay time < 1μs.

Optical properties of tsavorite Ca 3Al 2(SiO 4) 3:Cr 3+,V 3+ from Kenya

Previously, a relatively large splitting of the 2E g state of Cr 3+ in grossular Ca 3Al 2[SiO 4] 3 has been reported [M. Czaja and Z. Mazurak, Opt. Mater 3 (1994) 95]. The absorption and luminescence spectra of crystals containing Cr 3+ and V 3+in grossular Ca 3Al 2(SiO 4) 3 garnets (variety tsavorite) have been studied for the first time. From these spectra measured at room and liquid helium temperatures we determined energies of R 2, R 1, and 4T 2g levels of Cr 3+. The lifetimes and splitting of the 2E g state have been measured by tuning the excitation energy within the inhomogeneous profile of the R 1 and R 2 lines of the split 2E g → 4A 2g transition. To account for the thermal quenching of the R-lines, it is necessary to recognize that the two components of the doublet may have remarkably different radiative lifetimes (7500 and 2500 μs). These lifetimes were obtained from low temperature decay and from the temperature dependence of the intensity ratio of the R 2, R 1 components. These separate lifetimes as well as the lifetime of the 4T 2g state were then set to fit the temperature dependence of the joint effective lifetime. The optical fluorescence of a V 3+ dopant is characterized by the broad band infrared fluorescence spectrum associated with short decay time < 1μs.

Infrared emission from a polycyclic aromatic hydrocarbon (PAH) excited by ultraviolet laser

view Abstract Citations (48) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared Emission from a Polycyclic Aromatic Hydrocarbon (PAH) Excited by Ultraviolet Laser Cherchneff, Isabelle ; Barker, John R. Abstract The infrared fluorescence spectrum from the C-H stretch modes of vibrationally excited azulene (C10H8), a PAH was measured in the laboratory. PAHs are candidates as carriers of the unidentified infrared emission bands that are observed in many astronomical objects associated with dust and ultraviolet light. In the present experiment, gas phase azulene was excited with light from a 308 nm pulsed laser, and the infrared emission spectrum was time-resolved and wavelength-resolved. Moreover, the infrared absorption spectrum of gas phase azulene was obtained using an FTIR spectrometer. The laboratory emission spectrum resembles observed infrared emission spectra from the interstellar medium, providing support for the hypothesis that PAHs are the responsible carriers. The azulene C-H stretch emission spectrum is more asymmetric than the absorption spectrum, probably due to anharmonicity of levels higher than nu = 1. Publication: The Astrophysical Journal Pub Date: June 1989 DOI: 10.1086/185448 Bibcode: 1989ApJ...341L..21C Keywords: Aromatic Compounds; Azulene; Cyclic Hydrocarbons; Infrared Spectra; Interstellar Chemistry; Ultraviolet Lasers; Absorption Spectra; Emission Spectra; Fluorescence; Interstellar Matter; Molecular Excitation; Pulsed Lasers; Atomic and Molecular Physics; INFRARED: SPECTRA; INTERSTELLAR: GRAINS; INTERSTELLAR: MATTER; INTERSTELLAR: MOLECULES full text sources ADS | data products SIMBAD (2)

Theoretical fluorescence spectrum of 3HeT+ ions formed by the beta decay of tritium in T2.

Einstein transition probabilities for spontaneous emission within the $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$ ground state of $^{3}\mathrm{HeT}^{+}$ have been calculated and an infrared fluorescence spectrum of $^{3}\mathrm{HeT}^{+}$ ions formed during \ensuremath{\beta} decay in molecular tritium is discussed.