Absorption Cross-section Spectra Research Articles

A Revised Cross-Section Database for Gas Retrieval in the UV-Visible-Near IR Range, Applied to the GOMOS Retrieval Algorithm AerGOM

In this paper, we present the revision of the cross-section database used for the retrieval of aerosol and gas species from remote sensing measurements by the GOMOS instrument onboard ENVISAT. The absorption cross-section spectra concern ozone, nitrogen dioxide and nitrogen trioxide, for which improved datasets have been published since the implementation of the original GOMOS cross-section database in preparation of the ENVISAT mission. We evaluate the molecular absorption cross-section spectra currently available for O3, NO2 and NO3, and we present and discuss our selection of datasets and the set-up of the revised absorption cross-section database, with the focus on these three gases. The objective is to provide an optimal characterization of their absorption spectrum over the UV-visible-near IR range used by AerGOM, a retrieval algorithm that was designed to optimize the retrieval of aerosol species from GOMOS measurements. Despite its application to the specific case of GOMOS, it is the aim of this work to cover a more general scope than this particular mission, and to provide an evaluation applicable to any other case of remote sensing experiment covering the UV to near IR range, possibly with a high spectral resolution.

Absorption and Emission Spectroscopic Investigation of the Thermal Dynamics of the Archaerhodopsin 3 Based Fluorescent Voltage Sensor QuasAr1.

QuasAr1 is a fluorescent voltage sensor derived from Archaerhodopsin 3 (Arch) of Halorubrum sodomense by directed evolution. Here we report absorption and emission spectroscopic studies of QuasAr1 in Tris buffer at pH 8. Absorption cross-section spectra, fluorescence quantum distributions, fluorescence quantum yields, and fluorescence excitation spectra were determined. The thermal stability of QuasAr1 was studied by long-time attenuation coefficient measurements at room temperature (23 ± 2 °C) and at 2.5 ± 0.5 °C. The apparent melting temperature was determined by stepwise sample heating up and cooling down (obtained apparent melting temperature: 65 ± 3 °C). In the protein melting process the originally present protonated retinal Schiff base (PRSB) with absorption maximum at 580 nm converted to de-protonated retinal Schiff base (RSB) with absorption maximum at 380 nm. Long-time storage of QuasAr1 at temperatures around 2.5 °C and around 23 °C caused gradual protonated retinal Schiff base isomer changes to other isomer conformations, de-protonation to retinal Schiff base isomers, and apoprotein structure changes showing up in ultraviolet absorption increase. Reaction coordinate schemes are presented for the thermal protonated retinal Schiff base isomerizations and deprotonations in parallel with the dynamic apoprotein restructurings.

Absorption avoided resonance crossing of hybridization of silicon nanoparticles and gold nanoantennas

The near-field coupling between a high-refractive-index nanoparticle and gold nanoantennas is investigated theoretically. The absorption enhancement and also avoided resonance crossing in the absorption cross section spectra were observed with the hybridization system due to the coupling between the localized surface plasmon resonance of the gold nanoantennas and the magnetic dipole resonance of the silicon nanoparticle. By controlling the nanoparticle size or the separation distance, the near-field coupling can be tuned from the weak to the strong regime.

Sub-Poissonian photon statistics in quantum dot-metal nanoparticles hybrid system with gain media

In this paper, we theoretically demonstrate the sub-Poissonian photon statistics in gain-assisted quantum dot-metal nanoparticles (QD-MNPs) hybrid system with nanoscale footprint. The gain media is introduced to reduce the dissipation of localized surface plasmons and consequently the quality factor of MNPs is improved by adjusting the gain coefficient. Simulated by finite element method (FEM), the Fano resonance is observed in the absorption cross section spectrum of the hybrid system. Considering MNPs and gain media together as a single mode cavity, the system is investigated within the framework of cavity quantum electrodynamics by fitting necessary parameters with FEM. The numerical results show that the coupling between QD and MNPs falls in strong coupling regime and zero delay second-order autocorrelation function g2(0) = 0.356 can be achieved with proper choice of gain coefficient. Moreover, the sub-Poissonian photon statistics can be maintained in a large variation range of gain coefficient and a certain degree of detuning between QD and cavity is allowed.

Er,Yb:Ca3RE2(BO3)4 (RE=Y, Gd) – Novel 1.5 μm Laser Crystals

The search for new crystalline host materials for the usage in lasers emitting in the eye-safe spectral range of 1.5–1.6 µm is an important task. The aim of this work was to study the growth technique, spectroscopic properties and laser characteristics of new active media – crystals Er3+,Yb3+:Ca2RE2(BO3)4(RE=Y, Gd).Calcium-yttrium Er3+,Yb3+:Ca3Y2(BO3)4(CYB) and calcium-gadolinium Er3+,Yb3+: Ca2Gd2(BO3)4 (CGB) oxoborate crystals co-doped with erbium and ytterbium ions were investigated. Polarized absorption and emission cross-section spectra were determined. The lifetimes of4I11/2and4I13/2energy levels of Er3+ions were measured and ytterbium-erbium energy transfer efficiencies were estimated. The calculation of the gain cross-section spectra was performed. By using of Er3+,Yb3+: Ca2RE2(BO3)4 (RE=Y, Gd) crystals the laser performance was realized, for the first time to the best of our knowledge. The laser characteristics were studied in a quasi-CW (QCW) laser operation.The wide band with a peak at the wavelength of 976 nm is observed in the absorption spectra of both crystals. This peak coincides with the emission wavelength of the pump laser diodes for Yb-doped active media. The maximum value of absorption cross-section was 1.7 × 10–20cm2for polarizationE//bfor both crystals. The lifetimes of the upper laser level4I13/2of Er3+ions were 580 ± 30 μs and 550 ± 30 μs for Er,Yb:CYB and Er,Yb:CGB crystals, respectively. The energy transfer efficiencies from ytterbium to erbium ions for an Er,Yb:CYB and Er,Yb:CGB crystals were 94 % and 96 %, respectively. According to gain spectrum of the Er,Yb:CYB crystal the gain band peak is centered at the wavelength of 1530 nm. The maximum QCW output power was 0.5 W with slope efficiency of 13 % regarding to absorbed pump power for an Er,Yb: CYB crystal. The laser beam parameter M2did not exceed < 1.5.Based on the obtained results, it can be concluded that these crystals are promising active media for lasers emitting in the spectral range of 1.5–1.6 μm for the usage in laser rangefinder and laser-induced breakdown spectroscopy systems, and LIDARs.

Cross section spectral distribution of Er3+ electronic transitions in SrGdGa3O7 single-crystal

Abstract Visible and infrared absorption and emission spectra of Er3+-doped strontium gadolinium gallate (SrGdGa3O7) single-crystal were measured at room temperature. From the measured fluorescence spectra, the Er3+ emission cross section spectra were calculated at first. Then, by utilizing McCumber relation, the absorption cross section spectra were further calculated. In parallel, the absorption cross section spectra were also calculated from the measured absorption spectra of the crystal, and compared with those spectra calculated from the McCumber relation. The comparison shows that the absorption cross section spectra obtained using the McCumber relation are in reasonable agreement with those deduced from the measured absorption spectrum.

Validity of the McCumber Theory at High Temperatures in Erbium and Ytterbium-Doped Aluminosilicate Fibers

The temperature dependence of the emission and absorption cross sections of Er and Yb ions in rare-earth-doped aluminosilicate optical fibers is experimentally investigated. The obtained results demonstrate that the McCumber theory accurately predicts the temperature-induced changes of the emission cross section spectrum up to 500 °C when the absorption spectra measured at the considered temperature is used for the calculations instead of the one acquired at ambient temperature. Finally, we also demonstrate that the various heating steps up to 500 °C are not affecting the fiber guiding properties and no permanent effect is observed on the emission and absorption cross section spectra measured at room temperature.

Crystal growth, spectroscopy and first laser operation of a novel disordered tetragonal Tm:Na2La4(WO4)7 tungstate crystal

Tm3+:Na2La4(WO4)7, a disordered tetragonal scheelite-type tungstate crystal, is grown by the Czochralski method. The polarized absorption, stimulated-emission and gain cross-section spectra are determined. The maximum σSE is 1.62 × 10–20 cm2 at 1788.6 nm for σ-polarization. The Judd-Ofelt parameters for Tm3+ are Ω2 = 10.321, Ω4 = 0.183 and Ω6 = 2.122 [10–20 cm2]. The radiative lifetime of the 3F4 state is 1.63 ms. Raman spectroscopy reveals a maximum phonon energy of 923 cm−1. Laser operation under diode-pumping is achieved with both a-cut and c-cut Tm:Na2La4(WO4)7 crystals, reaching a maximum output power for the a-cut of 715 mW at ~ 1937 nm with a slope efficiency of 34%. Microchip laser operation using the c-cut crystal yields a slope efficiency of 41%. The Tm:Na2La4(WO4)7 crystal is promising for mode-locked lasers due to its broadband emission.

Semiempirical Atom-centered Density Matrix Propagation Approach to Temperature-dependent Vibrational Spectroscopy of Irinotecan

In the present study, a molecular dynamics study of irinotecan molecule with the atom-centered density matrix propagation scheme was carried out at AM1 semiempirical level of theory, at series of different temperatures, ranging from 5 K to 300 K. Molecular dynamics simulations were performed within the NVE ensemble, initially injecting (and redistributing among the nuclei) various amounts of nuclear kinetic energies to achieve the desired target temperatures. Subsequently to initial equilibration phase of 2 ps, productive simulations were carried out for 8 ps. The accuracy of simulations and the closeness of the generated trajectory to those at the Born-Oppenheimer surface were carefully followed and analyzed. To compute the temperature-dependent rovibrational density of states spectra, the velocity-velocity autocorrelation functions were computed and Fourier-transformed. Fourier-transformed dipole moment autocorrelation functions were, on the other hand, used to calculate the temperature-dependent infrared absorption cross section spectra. The finite-temperature spectra were compared to those computed by a static approach, i.e. by diagonalization of mass-weighted Hessian matrices at the minima located on the potential energy surfaces. Thermally-induced spectral changes were analyzed and discussed. The advantages of finite-temperature statistical physics simulations based on semiempirical Hamiltonian over the static semiempirical ones in the case of complex, physiologically active molecular systems relevant to intermolecular interactions between drugs and drug carriers were pointed out and discussed.

Spontaneous Symmetry Breaking Facilitates Metal-to-Ligand Charge Transfer: A Quantitative Two-Photon Absorption Study of Ferrocene-phenyleneethynylene Oligomers.

Change of the permanent molecular electric dipole moment, Δμ, in a series of nominally centrosymmetric and noncentrosymmteric ferrocene-phenyleneethynylene oligomers was estimated by measuring the two-photon absorption cross-section spectra of the lower energy metal-to-ligand charge-transfer transitions using femtosecond nonlinear transmission method and was found to vary in the range up to 12 D, with the highest value corresponding to the most nonsymmetric system. Calculations of the Δμ performed by the TD-DFT method show quantitative agreement with the experimental values and reveal that facile rotation of the ferrocene moieties relative to the organic ligand breaks the ground-state inversion symmetry in the nominally symmetric structures.

Photoactive n-type oxide AZO-AgNP-AZO multilayer films for photovoltaic application

We report on the simulation of the absorption cross-section of an aluminum-doped zinc oxide (AZO) - silver nanoparticles (AgNP)-AZO multilayer structure by the finite element method in Comsol Multiphysics. A key feature of our approach is consideration of two plasmon materials such as AgNP and highly doped AZO. The simulation is based on the Drude-Lorentz-Sommerfeld model. The absorption cross section spectra were obtained for structures with different thicknesses of AZO layers and different amounts of silver nanoparticles, and at a different incidence of illumination. As a result, several resonance peaks were detected in the absorption cross-section spectra. The enhancement of absorption in the visible and near-infrared regions of the spectrum is associated with plasmon oscillations of interacting silver nanoparticles and a plasmon resonance in an AZO nanolayer, respectively. The presence of several resonances in the visible region, as well as the resonance in the near-IR region, makes this material promising for photovoltaics.

Growth, spectroscopy, and laser operation of “mixed” vanadate crystals Yb:Lu1-x-yYxLayVO4

We report on the crystal growth, structure, Raman and optical spectroscopy of novel “mixed” tetragonal vanadates, Yb:Lu1-x-yYxLayVO4. Optical absorption, stimulated-emission, and gain cross-section spectra of Yb3+ are determined for π and σ polarizations. For a Yb:Lu0.74Y0.23La0.01VO4 crystal, the absorption bandwidth is >10 nm, the σSE is 1.1 × 10−20 cm2 at 1013 nm, the gain bandwidth is >40 nm (for π-polarization), and the radiative lifetime of the 2F5/2 state is ~305 μs. The Stark splitting of the Yb3+ multiplets is determined using low-temperature (6 K) spectroscopy. A diode-pumped a-cut 2 at.% Yb:Lu0.74Y0.23La0.01VO4 laser generated 5.0 W at 1044 nm with a slope efficiency of 43%. The developed materials are promising for sub-100 fs mode-locked lasers at ~1 µm.

Near-infrared incoherent broadband cavity enhanced absorption spectroscopy (NIR-IBBCEAS) for detection and quantification of natural gas components.

The principle of near-infrared incoherent broadband cavity enhanced absorption spectroscopy was employed to develop a novel instrument for detecting natural gas leaks as well as for testing the quality of natural gas mixtures. The instrument utilizes the absorption features of methane, butane, ethane, and propane in the wavelength region of 1100 nm to 1250 nm. The absorption cross-section spectrum in this region for methane was adopted from the HITRAN database, and those for the other three gases were measured in the laboratory. A singular-value decomposition (SVD) based analysis scheme was employed for quantifying methane, butane, ethane, and propane by performing a linear least-square fit. The developed instrument achieved a detection limit of 460 ppm, 141 ppm, 175 ppm and 173 ppm for methane, butane, ethane, and propane, respectively, with a measurement time of 1 second and a cavity length of 0.59 m. These detection limits are less than 1% of the Lower Explosive Limit (LEL) for each gas. The sensitivity can be further enhanced by changing the experimental parameters (such as cavity length, lamp power etc.) and using longer averaging intervals. The detection system is a low-cost and portable instrument suitable for performing field monitorings. The results obtained on the gas mixture emphasize the instrument's potential for deployment at industrial facilities dealing with natural gas, where potential leaks pose a threat to public safety.

Quantitative description of MLCT transitions in ruthenium polypyridyl complexes probed by two-photon absorption spectroscopy

Quantitative two-photon absorption (2PA) cross section and 2PA spectrum measurements were used to determine the molecular electric dipole change in the metal-to-ligand charge-transfer transition of ruthenium(II) tris-complexes of 2,2’-bipyridine ([Ru(bpy)3]2+) and 1,10-phenanthroline ([Ru(phen)3]2+) in several solvents.

Theoretical calculation of optical and magneto optical properties of magnetite nanorods

The optical and magneto-optical called Faraday rotation of composites containing isolated Fe3O4 (magnetite) nanorods particles are presented in the wavelength range from 300-700 nm. The results were obtained by using the discrete dipole approximation (DDA) method. The composite materials are constructed by combining Fe3O4 nanorods particles and the material with fixed dielectric constant of 2.25. The Fe3O4 nanorods of different aspect ratio (AR), varied from 3 to 7, were used to embed in the host material. The influence of the orientation of Fe3O4 nanorods comparing with the incident light and number particles on the Faraday rotation spectrum were also presented. The absorption cross-section spectra of Fe3O4 nanorods were able to be observed only when the main axis was aligned parallel to the polarization direction and perpendicular with the direction propagation of excited light.

Spectroscopy of Yb-doped tungsten–tellurite glass and assessment of its lasing properties

Glasses of the TeO2-WO3-Yb2O3 system are synthesized for wide range of Yb3+ concentrations of up to 6.0 × 1021 ions/cm3. The spectral-luminescent properties of lightly doped samples are investigated at room temperature and at the boiling point of liquid nitrogen. The energies of the Stark levels of the ground and excited states of Yb3+ ions incorporated into tungsten–tellurite glass are determined by analyzing the low-temperature spectra. The absorption, emission, and gain cross section spectra are obtained. The excess of the measured fluorescence decay time over the radiative lifetime ∼0.3 ms derived from the absorption spectra is attributed to the reabsorption effect in bulk samples. Measurements of lightly doped glass powder in the immersion liquid are made to reduce the effect of reabsorption. The fluorescence decay time of the powder is very close to the calculated radiative lifetime. Compared with phosphate, silicate, and other Yb3+-doped glasses, the tungsten–tellurite glass has a promising potential as a gain medium for lasers and amplifiers.

Absorption and Emission Spectroscopic Investigation of Thermal Dynamics and Photo-Dynamics of the Rhodopsin Domain of the Rhodopsin-Guanylyl Cyclase from the Nematophagous Fungus Catenaria anguillulae.

The rhodopsin-guanylyl cyclase from the nematophagous fungus Catenaria anguillulae belongs to a recently discovered class of enzymerhodopsins and may find application as a tool in optogenetics. Here the rhodopsin domain CaRh of the rhodopsin-guanylyl cyclase from Catenaria anguillulae was studied by absorption and emission spectroscopic methods. The absorption cross-section spectrum and excitation wavelength dependent fluorescence quantum distributions of CaRh samples were determined (first absorption band in the green spectral region). The thermal stability of CaRh was studied by long-time attenuation measurements at room temperature (20.5 °C) and refrigerator temperature of 3.5 °C. The apparent melting temperature of CaRh was determined by stepwise sample heating up and cooling down (obtained apparent melting temperature: 62 ± 2 °C). The photocycle dynamics of CaRh was investigated by sample excitation to the first inhomogeneous absorption band of the CaRhda dark-adapted state around 590 nm (long-wavelength tail), 530 nm (central region) and 470 nm (short-wavelength tail) and following the absorption spectra development during exposure and after exposure (time resolution 0.0125 s). The original protonated retinal Schiff base PRSBall-trans in CaRhda photo-converted reversibly to protonated retinal Schiff base PRSBall-trans,la1 with restructured surroundings (CaRhla1 light-adapted state, slightly blue-shifted and broadened first absorption band, recovery to CaRhda with time constant of 0.8 s) and deprotonated retinal Schiff base RSB13-cis (CaRhla2 light-adapted state, first absorption band in violet to near ultraviolet spectral region, recovery to CaRhda with time constant of 0.35 s). Long-time light exposure of light-adapted CaRhla1 around 590, 530 and 470 nm caused low-efficient irreversible degradation to photoproducts CaRhprod. Schemes of the primary photocycle dynamics of CaRhda and the secondary photocycle dynamics of CaRhla1 are developed.

Growth, spectroscopic properties, and laser action of Yb:YPO_4 crystal

Good-quality single crystals of Yb:YPO4 were grown in a high-temperature solution. Polarized absorption and emission cross-section spectra were determined by use of a plate-shaped crystal of 1.8 mm in thickness. Efficient continuous-wave laser action was achieved under diode end-pumping conditions, with output coupling changed in a wide range of 0.5%−40%. A maximum output power of 3.62 W was produced with a 1.0 mm thick crystal, with an optical-to-optical efficiency of 36%.

Infrared spectroscopic characterization of Na5Lu9F32 single crystals doped with various Er3+ concentrations

This work reports on optical spectra of Na5Lu9F32 single crystals doped with various Er3+ concentrations from 0.5 to 5 mol%. In our improved Bridgman method, the X-ray powder diffractions were investigated and optical parameters were also calculated by the Judd–Ofelt theory. Results showed that Er3+ ions entered the Lu3+ sites successfully without causing any obvious peak changes, and the doping concentration of Er3+ had important influence on the Er3+ local structure in Na5Lu9F32 crystals. The maximum emission intensities of ~1.5 and ~2.7 μm were obtained in present research when the doping concentration of Er3+ were 4 and 5 mol%, respectively, under the excitation of 980 nm LD. In these doping concentration, the maximum emission cross-sections were calculated to be 1.37 × 10−20 cm2 (~1.5 μm) and 2.1 × 10−20 cm2 (~2.7 μm). The gain cross-section at 2.7 μm was also estimated according to the absorption and emission cross section spectra. All these spectroscopic characterizations suggested that this fluoride crystal would possess promising applications in infrared lasers.

Infrared absorption cross-sections, radiative efficiency and global warming potential of HFC-43-10mee

HFC-43-10mee (C5H2F10) is a substitute for CFC-113, HCFC-141b and methyl chloroform, as well as an alternative to perfluorocarbons with high radiative efficiencies. Recent observations have shown that the global mean tropospheric abundance of HFC-43-10mee has increased steadily from the 1990s to reach 0.211ppt in 2012. To date, the emission of this compound is not regulated.The radiative efficiency (RE) of HFC-43-10mee has recently been re-evaluated at 0.42Wm−2ppb−1, giving a 100-year time horizon global warming potential (GWP100) of 1650. However, the initial RE, from which the new values were derived, originated from an unpublished source.We calculated a new RE of 0.36Wm−2ppb−1 and a GWP100 of 1410 from laboratory absorption cross-section spectra of a pure vapour of HFC-43-10mee. Acquisitions were performed in the 550–3500cm−1 spectral range using Fourier transform spectroscopy. The results were compared with the broadened spectra from the Pacific Northwest National Laboratory (PNNL) database and with theoretical calculations using density functional theory.