Measurements Of Excitation Spectra Research Articles

Interferometric excitation fluorescence lifetime imaging microscopy

Fluorescence lifetime imaging microscopy (FLIM) is a well-established technique with numerous imaging applications. Yet, one of the limitations of FLIM is that it only provides information about the emitting state. Here, we present an extension of FLIM by interferometric measurement of fluorescence excitation spectra. Interferometric Excitation Fluorescence Lifetime Imaging Microscopy (ixFLIM) reports on the correlation of the excitation spectra and emission lifetime, providing the correlation between the ground-state absorption and excited-state emission. As such, it extends the applicability of FLIM and removes some of its limitations. We introduce ixFLIM on progressively more complex systems, directly compare it to standard FLIM, and apply it to quantitative resonance energy transfer imaging from a single measurement.

Ultrafast supercontinuum sculpting for two-photon spectroscopy and microscopy of ratiometric fluorescent indicators

We present a compact laser system for quantitative two-photon excitation spectra measurements and ratiometric two-photon imaging of fluorescent protein indicators. The fundamental of the system is a short segment of photonic crystal fiber (PCF), which supports a nonlinear transformation of low-power ultrashort pulses by preserving temporal coherence, and this generates an ultrafast almost octave-spanning supercontinuum (SC). Accurate sculpting of the SC by its amplitude and phase modulation provides implementation of the spectroscopic and microscopic modalities. The spectroscopic one was exhibited by two-photon action cross section spectra measuring for the genetically encoded fluorescent sensing proteins of the vital biochemical parameters: acidity (SypHer3s), concentration of hydrogen peroxide (HyPer3 and HyPer7), redox status of NADH and glutathione (RexYFP and Grx1-roGFP2), hypohalous acids and their derivatives (Hypocrates). For the microscopy, we investigated and optimized the intensity pump pulse profiles under the high numerical objective by dispersion scan technique. We conducted real-time monitoring of the dynamics of hydrogen peroxide in HeLa cells with subcellular spatial resolution by means of ratiometric two-photon imaging of Hyper7 sensors. The presented hybrid laser system provides an ideal optical toolbox in order to develop ratiometric fluorescent sensors, which can be visualized in vivo using two-photon microscopy.

Electromagnetically Induced Transparency Spectra of 6Li Rydberg Atoms

Rydberg atoms possess highly excited valence electrons that are far away from atomic cations. Compared with ground states, Rydberg states are excited states with a high principal quantum number n that exhibit large electric dipole moments and have a variety of applications in quantum information processing. In this communication, we report the measurement of the 6Li Rydberg excitation spectrum by ladder-type electromagnetically induced transparency (EIT) in a vapor cell. The 2p→ns/nd EIT spectra were recorded by sweeping the frequency of an ultraviolet Rydberg pumping laser while keeping the probing laser resonant to the 2s→2p transition. All lasers were locked on an ultrastable optical Fabry-Pérot cavity and measured by an optical frequency comb. Our results provide valuable information to precisely determine quantum defects and enable novel experiments with Rydberg-dressed ultracold Fermi gases.

Down-/Up-conversion luminescence behaviors and energy transfer analysis in Tm3+ and Tm3+/Yb3+ co-doped tellurite glasses

Glasses with the chemical composition of (50-x-y) TeO2-30ZnO-10YF3-10NaF-0.5Tm2O3-yYb2O3 (y = 0.5, 1.0, and 3.0 mol%) are developed using a melt-quenching method. Measurements of absorption, excitation, down and up-conversion emission spectra, and decay times were used to investigate the energy transfer processes. Cross-relaxation mechanisms caused the emission intensity to decrease at higher Tm3+ ion concentrations. The Tm3+/Yb3+ co-doped glasses showed strong up-conversion emission under the diode laser excitation at 978 nm. Studies on the dependence of pump energy revealed the mechanism underlying the up-conversion luminescence. According to the findings, the developed Tm3+/Yb3+co-doped glasses are also found to be a promising option for spectral conversion and emission (visible and near infrared) applications.

Combustion synthesized novel SrAlBO4:Eu3+ phosphor: Structural, luminescence, and Judd-Ofelt analysis

A series of new phosphor SrAlBO4 doped by Eu³+ was synthesized by using very known Combustion method. The structural and optical properties explored using X-ray diffraction (XRD). The XRD pattern was matched well with the standard PDF card no. 1542236.The obtained phosphor had orthorhombic structure with space group Pccn (56). The image of Scanning electron microscope shows the external morphology of SrAlBO4 phosphor material, which revails the irregular morphology and the material showed the non uniform structure with agglomerates' size was size ranging in several micrometers. The confirmation of present element and their percentage also shown in the EDX image. The luminescence properties of rare earth activated SrAlBO4 phosphor were determined by measurement of excitation and emission spectra. The PL emission spectra of Eu3+ doped SrAlBO4 phosphor show characteristics bands at 590 nm & 614 nm which corresponds due to 5D0 →7F1 and 5D0 →7F2 transition of Eu3+ ions upon 395 nm excitation. The effect of different concentration of Eu3+ on luminescence emission intensity of SrAlBO4 phosphor was also studied. Further, concentration quenching is explained using Blasse's equation and Dexter's theory. Also, Judd-Ofelt analysis was performed on photoluminescence emission spectra. On investigation synthesized rare earth activated SrAlBO4 phosphor can be suitable for all lighting application devices.

Silver molecular clusters and the properties of radiophotoluminescence of alkali-phosphate glasses at high dose

This paper describes the results of radiophotoluminescence (RPL) measurements at high beta (90Sr/90Y) dose, including measurements of RPL intensity, excitation and emission spectra, and lifetimes, along with optical absorption measurements. Correction of the RPL intensity as the dose increases for absorption of the excitation light during RPL stimulation and the emitted light during RPL emission, reveals that the RPL intensities at emission wavelengths in the blue (470 nm) and orange (630 nm) peak at higher doses than previously reported. The corrected orange emission shows a linear-sublinear growth with dose with a peak intensity occurring at ∼10 kGy. The blue emission shows a linear-supralinear growth with a maximum as a function of dose not observed in the dose range used. This behavior is explained in terms of the growth of Ag molecular clusters, Ag2+ dimers and Ag42+ tetramers, as the dose increases. The growth of these clusters as a function of dose is modeled using rate equations and the simulated behavior is shown to match well the experimentally observed dose-response characteristics of the orange and blue RPL emissions. The growth of the Ag42+ tetramers with dose is also speculated to cause a decrease in the orange RPL sensitivity with increasing Linear Energy Transfer (LET quenching) at high LET values when this material is exposed to charged particles. Consequently it is hypothesized that blue RPL will not exhibit the same degree of LET quenching.

Nanodiamond-promoted white light emission in Eu, Dy, and Cu-containing phosphate glass: quantitative analysis and colorimetric study.

A thorough analysis of glass containing Eu2 O3 and Dy2 O3 , or Eu2 O3 , Dy2 O3 , and CuO melted together with nanodiamond powder was pursued based on measurements of optical absorption, photoluminescence (PL) emission and excitation spectra, and colorimetry. Nanodiamond facilitated the stabilization of Cu+ and Eu2+ ions with blue-emitting characteristics that, along with yellow-emitting Dy3+ and red-emitting Eu3+ led to the white light-emitting glass. Novel intensity notations implemented in intensity-based spectral ratios, and difference intensity correlation analysis were proposed for the assessment of PL properties. The chromaticity and correlated colour temperature of the emission were ultimately investigated as a two-parametric problem based on: (1) the different ionic components; and (2) the various excitation wavelengths employed. The optical analysis approach adds to the characterization methods to further fundamental understanding and provide helpful analytical tools for designing materials for tunable white light-emitting devices.

A Zn(II)-Metal-Organic Framework Based on 4-(4-Carboxy phenoxy) Phthalate Acid as Luminescent Sensor for Detection of Acetone and Tetracycline.

As hazardous environmental pollutants, residual tetracycline (TC) and acetone are harmful to the ecosystem. Therefore, it is necessary to detect the presence of these pollutants in the environment. In this work, using Zn (II) salt, 4-(4-carboxy phenoxy) phthalic acid (H3L), and 3,5-bis(1-imidazolyl) pyridine (BMP), a new metal-organic framework (Zn-MOF) known as [Zn3(BMP)2L2(H2O)4]·2H2O was synthesized using a one-pot hydrothermal method. The Zn-MOF has a three-dimensional framework based on the [Zn1N2O2] and [Zn2N2O4] nodes linked by a tridentate bridge BMP ligand and an L ligand with the μ1:η1η0/μ1:η1η0/μ0:η0η0 coordination mode. There were two kinds of left- and right-handed helix chains, Zn1-BMP and Zn1-BMP-Zn1-L. The complex was stable in aqueous solutions with pH values of 4-10. The Zn-MOF exhibited a strong emission band centered at 385 nm owing to the π*→π electron transition of the ligand. It showed high luminescence in some common organic solvents as well as in the aqueous solutions of pH 4-10. Interestingly, TC and acetone effectively quenched the luminescence of the Zn-MOF in aqueous solution and enabled the Zn-MOF to be used as a sensor to detect TC and acetone. The detection limits of TC and acetone were observed to be 3.34 µM and 0.1597%, respectively. Even in acidic (pH = 4) and alkaline (pH = 10) conditions, the Zn-MOF showed a stable luminescence sensing capability to detect TC. Luminescence sensing of the Zn-MOF for TC in urine and aquaculture wastewater systems was not affected by the interfering agent. Furthermore, the mechanism of sensing TC was investigated in this study. Fluorescence resonance energy transfer and photoinduced electron transfer were found to be the possible quenching mechanisms via UV-Vis absorption spectra/the excitation spectra measurements and DFT calculations.

Cryogenic Fluorescence Spectroscopy of Ionic Fluorones in Gaseous and Condensed Phases: New Light on Their Intrinsic Photophysics.

Fluorescence spectroscopy of gas-phase ions generated through electrospray ionization is an emerging technique able to probe intrinsic molecular photophysics directly without perturbations from solvent interactions. While there is ample scope for the ongoing development of gas-phase fluorescence techniques, the recent expansion into low-temperature operating conditions accesses a wealth of data on intrinsic fluorophore photophysics, offering enhanced spectral resolution compared with room-temperature measurements, without matrix effects hindering the excited-state dynamics. This perspective reviews current progress on understanding the photophysics of anionic fluorone dyes, which exhibit an unusually large Stokes shift in the gas phase, and discusses how comparison of gas- and condensed-phase fluorescence spectra can fingerprint structural dynamics. The capacity for temperature-dependent measurements of both fluorescence emission and excitation spectra helps establish the foundation for the use of fluorone dyes as fluorescent tags in macromolecular structure determination. We suggest ideas for technique development.

Low-temperature recombination luminescence of La-doped Ca2SnO4

Low-temperature ultraviolet-excited photoluminescence (PL) and recombination luminescence (RL) properties of La-doped Ca2SnO4 have been investigated by luminescence, electron paramagnetic resonance (EPR) and optically-detected magnetic resonance (ODMR) techniques. Two PL and RL bands at 340 nm and 450 nm have been observed. PL excitation spectra measurements with a synchrotron source showed a significant difference between the 450 nm and the 340 nm PL bands. The 450 nm band has a long-lasting hyperbolic decay, while the 350 nm band shows a fast decay. Assuming an excitonic nature of the 340 nm band, the band gap of the Ca2SnO4:La has been estimated to be approximately 5.5 eV. ODMR measurements suggest that the low-temperature RL band at 450 nm is caused by tunnelling recombination of electron trap and hole trap centres, and the recombination energy is transferred to Sn2+ luminescence centres.

White light emission and energy transfer in Pr3+/Er3+ co-doped InF3-based glass

Pr3+/Er3+ co-doped glasses based on InF3 were synthesized and then studied for white light emission. The emission spectra consist of several bands corresponding to characteristic 4f-4f electronic transitions of Pr3+ and Er3+ ions. The relative intensities of emission bands depend on the selective excitation wavelengths. The energy transfer process from Pr3+ to Er3+ ions was confirmed by the excitation and emission spectra measurements. From emission spectra, the CIE chromaticity coordinates, the correlated color temperature (CCT) and the color purity (CP) were determined. The results indicate that Pr3+/Er3+ co-doped glasses based on InF3 are excellent fluoride candidate to achieve warm white light emission.

Enhanced acoustofluidic mixing in a semicircular microchannel using plate mode coupling in a surface acoustic wave device

In this study, we present enhanced acoustic mixing inside a semicircular microfluidic channel via acoustic streaming induced by acoustic plate modes (APMs) of a 500-μm-thick double-side polished lithium-niobate (LiNbO3) substrate. We demonstrated that the APMs supported by the LiNbO3 substrate can be excited by an interdigitated transducer (IDT) at higher frequencies, in addition to conventional surface acoustic waves (SAWs), and can generate stronger acoustic streaming flow (ASF) and stirring effects. Consequently, rapid and enhanced mixing processes were observed in the channel. We conducted full-wave modeling of the device with finite element (FE) simulation to elucidate the acoustic process and mixing behaviors of the APM-based approach. Subsequently, we fabricated the acoustofluidic device using a standard photolithographic process and a 3D-printed replica molding method. The measured excitation spectrum of SAW and APM agrees with the numerical prediction; additionally, experiments on mixing and 2 µm particle motion in the continuous channel flow validate the ability of the device to enhance micromixing using APM frequencies compared with that using SAWs in our device. Our approach enables distinctive APMs to be fully coupled to the SAW-based acoustofluidic platform, which potentially enables an integrated design for the use of SAW and APM frequencies, acoustic energy, and wave fields in a single system. Our results also suggest innovative applications of the conventional SAW acoustofluidic devices to extended frequency regimes via APMs without reducing the substrate thickness and IDT pitch.

Study of the 71Π u state of sodium dimer by polarisation labelling spectroscopy

Two-colour polarisation labelling experiment measuring excitation spectra of Na in the spectral range 34, 600−39, 400 cm has furnished observation of the previously unknown electronic state. The excited state is characterised by a set of Dunham coefficients describing the f parity levels up to vibrational level v = 28 and the corresponding potential energy curve is constructed by the inverted perturbation approach method. Molecular parameters determined in the fit include ± 0.03 cm, ± 0.03 cm and ± 0.001 Å.

Modified Pechini method by PVP addition for Nd:Gd2O3 nanophosphors fabrication

Gadolinium oxide nanopowders doped with neodymium were prepared via modified Pechini method based on double stabilization of nanoparticles. Polyvinylpyrrolidone was used as an additional stabilizer at low-temperature stage of synthesis. This polymer also acts as a fuel during thermal treatment of precursors. Photoluminescence and FTIR spectroscopy, DTA/TG, XRD and SEM analysis were used for the analysis of thermal evolution of initial materials, chemical intermediates and final products at different stages of thermal treatment. Photoluminescence characterization included measurements of excitation and emission spectra of synthesized powders at different stages of thermal treatment.

Spin dynamics of the quantum dipolar magnet Yb3Ga5O12 in an external field

We investigate ytterbium gallium garnet Yb$_{3}$Ga$_{5}$O$_{12}$ in the paramagnetic phase above the supposed magnetic transition at $T_{\lambda} \approx 54$ mK. Our study combines susceptibility and specific heat measurements with neutron scattering experiments and theoretical calculations. Below 500 mK, the elastic neutron response is strongly peaked in the momentum space. Along with that the inelastic spectrum develops flat excitation modes. In magnetic field, the lowest energy branch follows a Zeeman shift in accordance with the field-dependent specific heat data. An intermediate state with spin canting away from the field direction is evidenced in small magnetic fields. In the field of 2 T, the total magnetization almost saturates and the measured excitation spectrum is well reproduced by the spin-wave calculations taking into account solely the dipole-dipole interactions. The small positive Curie-Weiss temperature derived from the susceptibility measurements is also accounted for by the dipole spin model. Altogether, our results suggest that Yb$_{3}$Ga$_{5}$O$_{12}$ is a quantum dipolar magnet.

Rydberg excitation spectrum ofK40ultracold Fermi gases

We report the measurement of the Rydberg excitation spectrum by two-photon process in ultracold $^{40}\mathrm{K}$ Fermi gases. Two different methods are employed to measure the Rydberg excitation spectrum, depending on the power of the probe laser. One scheme is to reduce atomic losses by means of electromagnetically induced transparency. The other is to enhance the atomic losses by spontaneous avalanche ionization due to the strong Rydberg-Rydberg interactions. We verify the consistency of both of the methods. The highest Rydberg states detectable in our experiment are limited to $n\ensuremath{\le}62$ due to the competition between the long Rydberg blockade effective range and the limited atomic cloud size.

Zeeman splitting features of electronic states of rare earth ions in TbF3 crystal

Optical absorption and photoluminescence (PL) spectra in the TbF3 crystals have been studied within the visible spectral range at the temperature of 90 K. Measurements of luminescence excitation spectra (LES) were carried out at temperatures of 25 and 300 K using the synchrotron radiation source. By comparison of PL and absorption spectra related to the optical transitions between Stark sublevels of 5D4 and 7F6 multiplets of Tb3+ ion at T = 90 K we can draw a diagram of the optical transitions between Stark sublevels and define their energies and positions in combining in optical transitions multiplets. It has been found that effect of the external magnetic field, which is parallel to a axis of the orthorhombic crystal, results in reduction of initial splitting of 10.7 cm−1 of well resolved doublet line of 7F6 → 5D4 absorption band observed in π polarization near 20,675 cm−1 with linear-polarized light propagated parallel to c crystallographic axis. At the same time in another experimental geometry, in which the external magnetic field is perpendicular to the a-b plane of the TbF3 crystal, an absorption line at ~20,730 cm−1 has the Zeeman splitting, which increases with the increase of magnetic strength. Such non-trivial behavior of the Zeeman effect in the TbF3 crystal is explained by peculiar features of magnetization of non-Kramers rare earth ions in crystal surroundings with CS symmetry, which is typical for crystallographic structure of trifluoride.

Structural Characteristics and Photoluminescence of Thin Films of Cu(In1–xgax)(Syse1–y)2 Solid Solutions

The phase composition and structural and optical characteristics of thin films of Cu(In1–xGax)(SySe1–y)2 solid solutions with the chalcopyrite structure were investigated. The unit-cell constants according to x-ray diffraction analysis were a ~ 5.720 A and c ~ 11.52 A. The elemental compositions were x = Ga/(Ga + In) ~ 0.14 and y = S/(S + Se) ~ 0.11 for Cu(In1–xGax)(S ySe1–y)2 thin films. The optical band gap of Cu(In1–xGax)(S ySe1–y)2 solid solutions determined from measurements of photoluminescence spectra and luminescence excitation spectra at ~4.2 K was Eg ~ 1.122 eV. The mechanism of radiative recombination of nonequilibrium charge carriers in thin films of Cu(In1–xGax) (S ySe1–y)2 solid solutions is discussed.

Phonon Sideband Analysis and Near-Infrared Emission in Heavy Metal Oxide Glasses.

In this work, spectroscopic properties of europium and erbium ions in heavy metal oxide glasses have been studied. The phonon energy of the glass host was determined based on Eu3+ excitation spectra measurements. Near-IR emission spectra at 1550 nm related to 4I13/2 → 4I15/2 transition of erbium in heavy metal glasses were examined with special regards to luminescence bandwidth and measured lifetime. In particular, correlation between phonon energy and the measured lifetime 4I13/2 (Er3+) was proposed. The luminescence lifetime for the 4I13/2 upper laser state of erbium decreases with increasing phonon energy in glass matrices. Completely different results were obtained glass samples with europium ions, where the 5D0 lifetime increases with increasing phonon energy. Our investigations suggest that the values of measured 5D0 lifetime equal to radiative lifetimes for all heavy metal oxide glasses.

Enhanced luminescence performances of Mn4+-activated Sr4Al14O25 red phosphors by doping with Sc3+ ions

A series of non-rare earth Mn4+-activated strontium aluminate phosphors Sr4Al14O25:Mn4+ co-doped with Sc3+ ions were successfully synthesized by a high-temperature solid-state reaction method. XRD result reveals that there is no introduction of additional phase but expansion of lattice with incorporation of Sc3+ ions. Excitation and emission spectrum measurement shows that the synthesized phosphors can be efficiently excited by near-ultraviolet and blue light, and a deep red emission centered at 652 nm with a narrow full width at half maximum (FWHM) can be obtained, which is attributed to the transition 2E→4A2 of Mn4+ ions. In addition, the crystal field strength parameter (Dq) and Racah parameters (B, C) and energies of states were calculated based on experimental data. Moreover, the luminous intensity of Sr4Al14-xScxO25:Mn4+ is enhanced and increased by 60% compared with Mn4+ single incorporated sample at x = 0.06. A phenomenon of redshift is observed in the excitation spectrum and discussed systematically. Finally, the mechanism of the positive effects with Sc3+ ions incorporated into lattice is discussed in detail. All the results suggest that the Sr4Al13.94Sc0.06O25:Mn4+ phosphor will become one of the great candidates for backlight of LCD.