V3 Band Research Articles

In-situ high-pressure behaviors of double-perovskite Sr2ZnTeO6

Structural and spectroscopic properties of Sr2ZnTeO6 (SZTO) were investigated by angle-dispersive synchrotron X-ray powder diffraction and Raman spectroscopy in a diamond anvil cell up to 31 GPa at room temperature. Although SZTO remained stable up to the highest pressure, the different pressure coefficients of the normalized axial compressibility were obtained as βab = 8.16 × 10−3 GPa−1 and βc = 7.61 × 10−3 GPa−1. The bulk modulus B0 was determined to be 190(1) GPa by fitting the pressure-volume data using the Birch-Murnaghan equation of state. All the observed Raman modes exhibited a broadening effect under high pressure. The vibrational band v1 around 765 cm−1, which is associated with the Te—O stretching mode in the basal plane of the TeO6 octahedron had the largest pressure coefficient, and the Grüneisen parameters for all the observed phonon modes were also calculated and presented. These parameters could be used to measure the amount of uniaxial or biaxial strain, providing a fundamental tool for monitoring the magnitude of the shift of phonon frequencies with strains.

VUV spectroscopy of formamide ices

Vacuum UltraViolet (VUV) spectra of formamide ice have been studied using synchrotron radiation. VUV spectra of formamide ice recorded at 30K revealed two photoabsorption bands, historically labelled V1 and Q in gas phase VUV spectra. However, in contrast to such gas phase spectra the Q band was found to be more intense than the V1 band in the ice spectra. At higher temperatures changes observed in the spectra have been ascribed to the rearrangement of formamide dimers within the ice. At 160K a phase change from amorphous to crystalline ice was also observed, at higher temperatures (200K) there is some evidence of possible polymerization within the ice.

Structure and magnetic properties of Co–Ni–Li ferrites synthesized by citrate precursor method

Nanoparticles of Co0.5Ni0.5−2xLixFe2+xO4 with x ranging from 0.00 to 0.25 in steps of 0.05 were prepared by using citrate precursor method. The microstructure and the magnetic properties of the as-prepared nanosamples and the effect of increasing Li1+ ions on their physical properties were studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), particle size analyzer (PSA), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM) were used to investigate the samples. The XRD analysis confirmed the cubic spinel phase formation of the prepared samples, while TEM images and PSA ensure the nanostructural features of them. The FTIR spectra reveal the presence of two prominent absorption bands v1 and v2 in the range of 600 and 400cm−1 which are usually attributed to the tetrahedral and octahedral complexes of the spinel lattice, respectively. The change of v2 gradually towards lower frequency and the slightly change of v1 were explained depending on the effect of increasing Li1+ content on the bond length of B-site metal ions and the spin canting of A-site metal ions, respectively. Saturation magnetization and remnant magnetization were found to increase with adding Li1+ ions up to x=0.15 and then to decrease again, while coercivity decreases monotonically by increasing Li1+ ions. The change in magnetic properties by adding Li1+ ions is explained as to be dependent on many factors such as crystallite size, measured density, porosity, expected cation distribution, A–B exchange interactions, and magnetocrystalline anisotropy.

NON-LTE EFFECTS ON THE H3+ROVIBRATIONAL POPULATION IN THE JOVIAN IONOSPHERE

We investigate non-LTE effects on the H₃? level populations to help the analysis of the observed 2 and 3.5 micron H₃? emissions from the Jovian ionosphere. We begin by constructing a simple three-level model, in order to compute the intensity ratio of the R(3,4) line in the hot band to the Q(1,0) line in the fundamental band, which have been observed in the Jovian auroral regions. We find that non-LTE effects produce only small changes in the intensity ratios for ambient H₂ densities less than or equal to 5×10 11 ㎝ ?3 . We then construct two comprehensive models by including all the collisional and radiative transitions between pairs of more than a thousand known H₃? rovibrational levels with energies less than 10000 ㎝ ?1 . By employing these models, we find that the intensity ratios of the lines in the hot and fundamental bands are affected greatly by non-LTE effects, but the details depend sensitively on the number of collisional and radiative transitions included in the models. Non-LTE effects on the rovibrational population become evident at about the same ambient H₂ densities in the comprehensive models as in the three-level model. However, the models show that rotational temperatures derived from the intensities of rotational lines in the v₂ and 2v₂ bands may differ significantly from the ambient temperatures in the non-LTE regime. We find that significant non-LTE effects appear near and above the H₃? peak, and that the kinetic temperatures in the Jovian thermospheric temperatures derived from the observed line ratios in the 2 and 3.5 micron H₃? emissions are highly model dependent.

Experiment research on ellipsoidal structure methane using the absorption characteristics of 3.31 μm mid-infrared spectroscopy

The intensity distribution of absorption spectroscopy of methane mid-infrared fundamental absorption bands, near-infrared combination band of v2+2v3 and overtone band of 2v3 were discussed in details in this paper. Quantitative data showed that the absorption intensities of fundamental bands are twice larger than overtone bands, and three times larger than combination bands. Based on the methane 3.31μm (v3) fundamental absorption bands and differential signal disposal method, a rotational ellipsoidal light structure was designed using ordinary light source and detector to improve gas detection sensitivity. The experimental results of concentration detection showed that the precision of concentration measurement can reach 3% and detection sensitivity is 50ppm. Meanwhile, experiment was performed to investigate the influence of temperature on mid-infrared absorption performance of methane and the experience curve of 3.31μm (v3) fundamental absorption signal depending on temperature and its rate of change was drawn.

Low temperature-fired Ni-Cu-Zn ferrite nanoparticles through auto-combustion method for multilayer chip inductor applications

Ferrite nanoparticles of basic composition Ni0.7-xZnxCu0.3Fe2O4 (0.0 ≤ x ≤ 0.2, x = 0.05) were synthesized through auto-combustion method and were characterized for structural properties using X-ray diffraction [XRD], scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy [FT-IR]. XRD analysis of the powder samples sintered at 600°C for 4 h showed the cubic spinel structure for ferrites with a narrow size distribution from 28 to 32 nm. FT-IR showed two absorption bands (v1 and v2) that are attributed to the stretching vibration of tetrahedral and octahedral sites. The effect of Zn doping on the electrical properties was studied using dielectric and impedance spectroscopy at room temperature. The dielectric parameters (ε', ε″, tanδ, and σac) show their maximum value for 10% Zn doping. The dielectric constant and loss tangent decrease with increasing frequency of the applied field. The results are explained in the light of dielectric polarization which is similar to the conduction phenomenon. The complex impedance shows that the conduction process in grown nanoparticles takes place predominantly through grain boundary volume.PACS: 75.50.Gg; 78.20; 77.22.Gm.

The v3 band of 14C16O2 molecule measured by optical-frequency-comb-assisted cavity ring-down spectroscopy

The infrared spectrum of the rare isotopologue has been investigated in the range 2190–2250 cm−1 with a frequency-comb-referenced cavity ring-down spectrometer. Thirty-three ro-vibrational transitions of the ν3 fundamental band have been detected. Their absolute frequency was measured with a relative uncertainty ranging from to . The experimental frequencies were fitted to the conventional Hamiltonian of a linear molecule and a new set of spectroscopic parameters for the fundamental vibrational state has been improved for this species.

HNC/HCN Ratio in Acetonitrile, Formamide, and BrCN Discharge

Time-resolved Fourier transform (FT) spectrometry was used to study the dynamics of radical reactions forming the HCN and HNC isomers in pulsed glow discharges through vapors of BrCN, acetonitrile (CH(3)CN), and formamide (HCONH(2)). Stable gaseous products of discharge chemistry were analyzed by selected ion flow tube mass spectrometry (SIFT-MS). Ratios of concentrations of the HNC/HCN isomers obtained using known transition dipole moments of rovibrational cold bands v(1) were found to be in the range 2.2-3%. A kinetic model was used to assess the roles the radical chemistry and ion chemistry play in the formation of these two isomers. Exclusion of the radical reactions from the model resulted in a value of the HNC/HCN ratio 2 orders of magnitude lower than the experimental results, thus confirming their dominant role. The major process responsible for the formation of the HNC isomer is the reaction of the HCN isomer with the H atoms. The rate constant determined using the kinetic model from the present data for this reaction is 1.13 (±0.2) × 10(-13) cm(3) s(-1).

A NEWLY DEVELOPED FLUORESCENCE MODEL FOR C2H6ν5AND APPLICATION TO COMETARY SPECTRA ACQUIRED WITH NIRSPEC AT KECK II

Accurate rotational temperatures are essential for extracting production rates for parent volatiles in comets. Two strong bands of ethane (v7 at 2985.39/cm and v5 at 2895.67/cm) are seen in infrared cometary spectra, but the Q-branches of v7 are not resolved by current instruments and cannot provide an accurate rotational temperature with current models.We developed a fluorescence model for the C2H6 v5 band that can be used to derive a rotational temperature.We applied our C2H6 5 model to high-resolution infrared spectra of the comets C/2004 Q2 Machholz and C/2000 WM1 (LINEAR), acquired with the Near-infrared Echelle Spectrograph on the Keck II telescope. We demonstrate agreement among the rotational temperatures derived from C2H6 v5 and other species, and between mixing ratios derived from C2H6 v5 and C2H6 v7. As a symmetric hydrocarbon, C2H6 is observed only in the infrared, and it is now the fifth molecule (along with H2O, HCN, CO, and H2CO) for which we can derive a reliable rotational temperature from cometary infrared spectra.

Offset-frequency locking of extended-cavity diode lasers for precision spectroscopy of water at 138~$\mu$m

We describe a continuous-wave diode laser spectrometer for water-vapour precision spectroscopy at 1.38 μm. The spectrometer is based upon the use of a simple scheme for offset-frequency locking of a pair of extended-cavity diode lasers that allows to achieve unprecedented accuracy and reproducibility levels in measuring molecular absorption. When locked to the master laser with an offset frequency of 1.5 GHz, the slave laser exhibits residual frequency fluctuations of 1 kHz over a time interval of 25 minutes, for a 1-s integration time. The slave laser could be continuously tuned up to 3 GHz, the scan showing relative deviations from linearity below the 10{-6} level. Simultaneously, a capture range of the order of 1 GHz was obtained. Quantitative spectroscopy was also demonstrated by accurately determining relevant spectroscopic parameters for the 22,1→22,0line of the H2(18)O v1+v3 band at 1384.6008 nm.

Electron–Phonon Coupling Assisted Emission in Single Magnetic La<SUB>0.67</SUB>Ca<SUB>0.33</SUB>MnO<SUB>3</SUB> Domains of Thin Nanoplates

A chemical method with small polymer templates is explored to obtain single magnetic domain La0.67Ca0.33MnO3 particles of thin nanoplates (25-35 nm thickness). The sample is light-emitting (480-800 nm) in multiple bands with two prominent bandgroups in the 570 nm green and 762 nm red emissions. The green emission consists of four bands 555.1, 565.7, 573.4, and 584.7 nm in the O2- -2p--> Mn3+ / Mn4+ -3d interband electronic transitions. Two excited-electronic levels G, (565.7 nm) and G2 (555.1 nm), which are exchange coupled via a phonon level v2* (678 cm(-1)), exhibit the four bands in the transitions to the ground state G0 and a phonon level v1 (575 cm(-1)). The bands v1 and v2 are well-resolved in the IR spectrum. A similar phonon assisted Mn3+ --> Mn4+ charge transfer transition results in the red emission. Both the green and red bandgroups appear in a common excitation over 350-450 nm from a xenon source. Evidently, as proposed with a model energy level diagram, the electron-phonon coupling governs a multiple light-emission in this example of the single domain particles. Otherwise, such specific ceramics of half-metallic ferromagnets hardly allows a light-emission at room temperature.

Infrared diode laser spectroscopy

AbstractThree types of lasers (double-heterostructure 66 K InAsSb/InAsSbP laser diode, room temperature, multi quantum wells with distributed feedback (MQW with DFB) (GaInAsSb/AlGaAsSb based) diode laser and vertical cavity surface emitting lasers (VCSELs) (GaSb based) have been characterized using Fourier transform emission spectroscopy and compared. The photoacoustic technique was employed to determine the detection limit of formaldehyde (less than 1 ppmV) for the strongest absorption line of the v3 + v5 band in the emission region of the GaInAsSb/AlGaAsSb diode laser. The detection limit (less than 10 ppbV) of formaldehyde was achieved in the 2820 cm−1 spectral range in case of InAsSb/InAsSbP laser (fundamental bands of v1, v5). Laser sensitive detection (laser absorption together with high resolution Fourier transform infrared technique including direct laser linewidth measurement, infrared photoacoustic detection of neutral molecules (methane, form-aldehyde) is discussed.Additionally, very sensitive laser absorption techniques of such velocity modulation are discussed for case of laser application in laboratory research of molecular ions. Such sensitive techniques (originally developed for lasers) contributed very much in identifying laboratory microwave spectra of a series of anions (C6H−, C4H−, C2H−, CN−) and their discovery in the interstellar space (C6H−, C4H−).

The Settlement and Remote - Measured Spectra of Absorption of V3 Bands of Methane and Their Analysis

It is lead settlement works and remote research of a spectrum of absorption of ν3 bands of methane in a range of lengths of waves 3.25–3.45 microns. Time forms and intensity of separate lines P- and R-branches are calculated. Comparison of experimentally measured and settlement spectral width and intensity separate lines of ν3 strips of methane is lead. The received results allow finding optimum values of optical parameters of probing tunable parametrical laser radiation. Settlement values of spectral width and intensity separate lines of ν3 bands of methane it will well be coordinated with the measured experimental sizes.

Evolution of the optical absorption spectra and electronic structure of the VBO3 crystal under high pressures

The evolution of optical absorption spectra of the ferromagnetic semiconductor VBO3 under high pressures up to 70 GPa has been investigated. It has been revealed that, below the fundamental absorption edge (Eg1 = 3.02 eV), the spectra exhibit a series of bands V1 (2.87 eV), V2 (2.45 eV), V3 (1.72 eV), and V4(1.21 eV) due to the d-d transitions in the V3+ ion and charge-transfer excitations. A model of the electronic structure of the VBO3 semiconductor has been constructed. This model combines the one-electron description of the s and p states of boron and oxygen and the many-electron description of the vanadium d states.

Fourier transform infrared spectroscopy measurements of H2O-broadened half-widths of CO2 at 4.3 μmThis article is part of a Special Issue on Spectroscopy at the University of New Brunswick in honour of Colan Linton and Ron Lees.

To support remote sensing of carbon dioxide in the troposphere, H2O pressure-broadened half-widths were obtained for 182 lines of CO2 in the 2250–2390 cm–1 region. For this, six spectra of CO2 were recorded at 0.003 89 cm–1 resolution using a Bruker IFS-125HR at the Jet Propulsion Laboratory. The absorption cell length was 6.14 cm, and the water pressures ranged from 20.1 to 26.5 torr (1 torr = 133.322 4 Pa) near room temperatures. Partial pressures of the species in the mixtures were determined by measuring selected line intensities in the v3 band of CO2 and the v2 band of H2O. Sample temperatures were validated by deriving rotational temperature from the v3 and v2 + v3 – v2 intensities of 12CO2 and those of CO (1–0). Positions, intensities, and half-widths were retrieved spectrum by spectrum using a nonlinear least-squares line-fitting algorithm, employing a standard Voigt line shape profile and an instrumental line shape consisting of a sinc function with aperture correction. Half-widths obtained for both the fundamental and the hot band of 12CO2 and the fundamental v3 band of 13CO2 had similar values. While half-widths of CO2 broadened by other atmospheric gases (such as N2, O2, CO2, and air) tend to decrease with increasing rotational quantum number J″, the H2O-broadened half-widths were observed to increase for intermediate J′′ (8 ≤ J′′ ≤ 42): ∼0.127 cm–1 atm–1 near J′′ = 8, and increasing to ∼0.143 cm–1 atm–1 (1 atm = 101.325 kPa) towards J″ = 42. Moreover, for 10 ≤ J″ ≤ 40, the empirical widths were within ∼2%−3% of theoretical calculations. Since water vapor could reach up to 5% of ambient atmospheric surface pressure in the tropical regions, water broadened half-widths are required to model tropospheric CO2, particularly for high-precision remote sensing, to achieve a sub-percent precision in the measurements of CO2 column averaged mixing ratio. Since little vibrational dependence in line broadening has been seen, these results at 4.3 µm can be used for other bands of CO2.

Resonance Raman Studies of Carotenoid Molecules Within Photosystem I Particles

ABSTRACTIn higher plants, carotenoid molecules play particularly important roles in harvesting light, stabilizing protein structures, regulating energy flow, and dissipating excess energy not required by the organism for photosynthesis. Low-temperature resonance Raman spectroscopy was used to study the spectral properties, binding sites and composition of major carotenoids in spinach Photosystem I particles. Photosystem I is a supercomplex of a reaction centre, core and light-harvesting complexes. Resonance Raman spectra of carotenoid molecules have four main groups of intense bands, which provide information on the conformation and configuration of these molecules. The most sensitive to their molecular configurations relaxed or distorted is v4 band exhibiting an increase in both intensity and structure indicating out-of-plane distortion of the molecule. During prolonged exposure to high-light intensities various pigments in Photosystem I exhibited different susceptibility to photodestruction. Resonance Raman technique allowed us to recognize the type and conformation of photobleached carotenoid molecules and to reveal the involvement of these pigments in the photoprotection. Raman data revealed a nearly full photobleaching of the long-wavelength lutein molecules. The observed similar bleaching rate of the lutein molecules and the most red-shifted long-wavelength chlorophyll a, located in the antenna membrane protein Lcha4, suggested that these molecules are located closely. Our results showed that the photobleached antenna pigments and especially luteins and the most long-wavelength absorbing chlorophylls are involved in photoprotection of PSI core complex. We investigated the effect of histidine on the photobleaching of pigments in isolated particles of photosystem I. Our preliminary results showed that histidine reduces the photobleaching of antenna pigments and especially luteins and the most long-wavelength absorbing chlorophylls located in PSI antenna complex.

Nitrogen-pressure shifts in the ν3 band of methane measured at several temperatures between 300 and 90 K

Remote sensing of the Earth's atmosphere requires accurate knowledge of spectroscopic line parameters for the molecules investigated. Knowledge of the temperature dependence of these parameters is also essential if agreement, at the noise level, between calculated and experimental data is to be achieved. The authors recently published results of nitrogen broadening measurements in the v3 band of 12CH4 using the 5.37 m long absorption path length all-copper Herriott cell. The temperature dependent line parameters determined in the laboratory were applied to fit a portion of the atmospheric spectrum recorded with a balloon-borne remote sensing FTIR instrument, called the Limb Profile Monitor of the Atmosphere, and operating in absorption against the sun. Since the authors had a relatively complete series of data for the P(9) transition in the v3 band of 12CH4, the A2 1 as well as the F2 1, F1 1 and A1 1 lines recorded at different pressures and at four temperatures between 300 and 90 K, we reanalyzed the data to derive pressure shift information at different temperatures. The temperatures for which data were collected and analyzed are 298, 140 and 90K. The high precision pressure shift data obtained here over a large range of temperature demonstrate the ability of our experimental arrangement to address specific questions on a given spectral window like in the balloon experiment or in a satellite project, for example.

Update of line parameters of ozone in the 2550-2900 cm^−1 region

An update of spectroscopic line parameters for the 3.45-3.92 microm ozone bands is reported. The line list includes the parameters of 15 bands of the main isotopic species and of the v1+v2+v3 band of 16O16O18O and 16O18O16O. The results are based on previous high resolution laboratory studies. Comparisons of experimental spectra with an absorptance simulation of ozone based on the reported line list shows that the latter one is accurate enough for strong, medium, and weak transmittance in the 2550-2900 cm(-1) spectral range. The data are available on the Web in the Spectroscopy and Molecular Properties of Ozone (S&MPO, http://smpo.iao.ru and http://ozone.univ-reims.fr) and HITRAN (http://cfa-www.harvard.edu/hitran/) databanks.

時間分解フーリエ変換赤外分光法の開発と星間化学研究への応用

By using a high-resolution spectrometer, a time-resolved Fourier transform infrared spectroscopic method has been developed with the help of a microcontroller SX and/or FPGA, where a maximum of 64 time-resolved data are recorded with a preset time interval in a single scan of the interferometer. This method has been applied to ob-servations of infrared emission spectra from pulsed discharge products such as CN, He2, H+3, HNC/HCN. He2 in Rydberg states with higher energy than the b3II state was found to be produced efficiently in afterglow plasma, and the quantum defect theory was applied to identification of each line in electronic states originated from 5f and 6f orbitals. From the observed timeprofiles of emission lines of the H+3 v2 band, the rate constant for recombination reaction of H+3 and electon has been estimated. The time-resolved sytem was also applied for emission lines from laser ablation products by using a high repetition rate Nd: YLF laser.

Line intensities of the asymptotic asymmetric-top radical HO2 at high temperatures

The total internal partition sums were calculated in the product approximation at temperatures up to 5000 K for the asymptotic asymmetric-top HO2 molecule. The calculations of the rotational partition function and the vibrational partition function were carried out with the rigid-top model and in the harmonic oscillator approximation, respectively. Our values of the total internal partition sums are consistent with the data of HITRAN database with -0.14% at 296 K. Using the calculated partition functions, we have calculated the line intensities of v2 band of HO2 at several high temperatures. The results showed that the calculated line intensities are in very good agreement with those of HITRAN database at temperatures up to 3000 K, which provides a strong support for the calculations of partition functions and line intensities at high temperatures. Then we have extended the calculation to higher temperatures. The simulated spectra of v2 band of the asymptotic asymmetric-top HO2 molecule at 4000 and 5000K are also obtained.