Relative Wavenumber Research Articles

ACCURATE LABORATORY WAVELENGTHS OF THE 1910 Å Ti II RESONANCE TRANSITIONS RELEVANT TO STUDIES OF POSSIBLE VARIATIONS OF THE FINE-STRUCTURE CONSTANT

In recent years, the analysis of absorption lines in quasi-stellar object (QSO) spectra, using the many-multiplet (MM) method, has provided evidence for space-time variations in the fine-structure constant, ?. Future studies aim to reduce systematic errors in these measurements by considering a greater number of transitions, but this is only possible for lines where high-precision laboratory standards exist. Two transitions of high importance for future MM analyses, but which currently lack accurately measured wavelengths, are the Ti II transitions observed at 1910 ?. We report accurate measurements of these transitions by high-resolution Fourier transform spectroscopy, giving line wavenumbers of (52,329.889 ? 0.001) cm?1 and (52,339.240 ? 0.001) cm?1. Lines from other important Ti II, Mg I, Mg II, and Zn II transitions were measured simultaneously, minimizing their relative wavenumber uncertainties, and permitting the newly measured 1910 ? Ti II line wavenumbers to be linked directly to lines from other studies.

Analytical and numerical solutions for the flow in microtube with three-dimensional corrugated surface, part 1: steady flow

The influences of three-dimensional corrugated wall on the fully-developed steady no-slip flows in microtube are studied by analytical and numerical methods in this article. Detailed analytical solutions for the space-averaged equations and the numerical method for the solutions of the disturbance equations are given. An iterative arithm of coupled equations with respect to space-averaged velocities and disturbance velocities is suggested. The study shows that a three-dimensional subsidiary stress layer exists in the near-wall region. The relative roughness, wavenumber and Reynolds number are three important parameters influencing the subsidiary stresses and the space-averaged pressure drop. The space-averaged pressure drop subject to an invariable flow rate mainly depends on the position of datum surface. When the datum surface is taken at the balance position of wall function, the value of pressure drop is determined by the dynamic characteristics of the flow.

Surface-enhanced Raman scattering (SERS) of a copper electrode in 1- n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

The electrochemical behaviour and surface-enhanced Raman scattering (SERS) effect exhibited by a copper electrode in 1- n-butyl-3-methylimidazolium tetrafluoroborate (BMI·BF 4) ionic liquid were investigated. It was shown that copper presents an electrochemical window of approximately 2.5 V in BMI·BF 4. Characteristic Raman and infrared active phonons of a Cu 2O film were detected prior to SERS activation. It was shown that at potentials less negative than −1.2 V, there is an excess of BF 4 - ions on the electrode surface, but they do not interact with the copper surface. Remarkable changes in the relative intensities and wavenumber positions of vibrational modes containing imidazolium ring motions were observed at potentials more negative than −1.2 V and were attributed to the interaction of the imidazolium ring with the copper surface through a partial charge transfer process.

2.01] A comparative Raman and CARS imaging study of colon tissue

Objective This paper presents an experimental evaluation of the information content, which can be obtained from using the complementary strengths of Raman and Coherent anti-Stokes Raman (CARS) microspectroscopy. Material and methods CARS images were recorded from thin colon tissue sections at various relative wave number detunings and compared with Raman images. Raman images were analyzed by chemical mapping, representing a univariate algorithm and by k -means clustering, representing a multivariate algorithm. The colon-tissue samples used in this study were obtained by resection from patients undergoing surgery (diverticulitis, colorectal carcinoma, Crohn's disease), and frozen at −80 °C without fixative or tissue embedding media. 10 μm-tissue sections were prepared using a cryotome, transferred onto quartz slides for Raman spectroscopy, and dried. The study protocol was approved by the local ethics commission. Results CARS images were recorded at different Stokes shifts allowing for selective protein and lipid bands to be probed resonantly. All CARS images correlate well with the photomicrographs because the non-resonant signals provided significant morphological information. The chemical contrast can be enhanced by compensation of the non-resonant background. All CARS images also correlate well with the Raman images. The amount of time of acquisition of Raman images was incomparably greater (by a factor of 1000) than for the acquisition of CARS images. The resulting Raman images probed only small areas in the 20×20 μm 2 range. However, complete spectral information could be extracted from Raman images. Extended spectral ranges are required to distinguish different tissue types in colon pathologies such as inflammation or colorectal cancer. Conclusion Based on the current results we suggest a complementary application of Raman and CARS imaging. Raman imaging defines spectral regions and spectral markers that are essential for tissue classification. CARS imaging at different Stokes shifts or in the multiplex mode, probes these spectral descriptors at video-rate speed. Such a combination offers very good prospects for clinical diagnoses.

Laboratory wavelengths for cosmological constraints on varying fundamental constants

Cosmological investigations, using high-redshift quasi-stellar object (QSO) absorption spectra, of possible variations of the fine-structure constant (α) require very accurate laboratory wavelengths for a number of resonance transitions from several different species. A change in α could be detected as a shift in the wavelengths of atomic transitions in the QSO systems and to accurately determine the values of such shifts it is essential that the laboratory rest wavelengths are known to a high degree of accuracy and precision. The present status of such laboratory wavelengths is discussed with emphasis on our recent study including laboratory wavelengths and wavenumbers of ultraviolet (UV) resonance lines from seven species, measured using the UV high-resolution Fourier transform spectrometer in Lund. The high relative accuracy of the wavenumbers has been obtained by the use of a composite hollow-cathode light source, which enables the spectra of the different species to be recorded simultaneously and thereby minimizes the effects from several steps of calibration. Much emphasis has been put on investigations of possible wavenumber shifts from line structure and self-absorption as well as pressure shifts and calibration effects. The absolute as well as the relative wavenumber accuracy is discussed and the wavenumbers are compared with values from other investigations.

Whistler wave stabilization/destabilization of drift waves in a plasma cylinder

The nonlinear coupling of a large amplitude whistler wave with low frequency drift waves in an inhomogeneous magnetized plasma cylinder is investigated. The coupling produces whistler wave sidebands. The pump and sidebands exert a ponderomotive force on electrons causing a frequency shift in the drift wave, leading to its stabilization/destabilization, depending on the relative wave numbers of the interacting waves as well as with whistler pump power. The whistler wave stabilizes the drift wave for K0z < 2.9 × 102 and destabilizes for K0z > 2.9 × 102, with K0z = k0zc/ωci, where k0z is the wave number of the whistler pump, c is the velocity of light and ωci is the ion cyclotron frequency. The whistler pump power above 5 MW also stabilizes the drift wave.

Raman spectroscopy of pure H2O and NaCl-H2O containing synthetic fluid inclusions in quartz—a study of polarization effects

The O-H stretching region of the Raman spectrum of aqueous solutions (H2O-NaCl mixtures) is a set of poorly defined broad bands between 2,800cm−1 and 3,800cm−1. The morphology of this spectral region is systematically characterised by deconvolution, using three Gaussian–Lorentzian contributions. This method allows a purely geometrical description of the spectra of pure H2O as well as saline solutions at room temperatures. A pure H2O reference solution has peak positions at 3,223cm−1 (Peak1), 3,433cm−1 (Peak2) and 3,617cm−1 (Peak3). The morphology of the Raman bands is influenced by the presence of NaCl in the aqueous solution. The variation in Peak1 values is correlated with the salinity of the aqueous solutions according to the equation: $$\Delta \,v_1 = \,3222.8\,\, + \,\,1.69\,sal$$ where sal is the salinity (in mass%) and Δν1 is the relative wavenumber (cm−1) of Peak1. The contours of the Raman spectra of aqueous solutions in fluid inclusions in quartz are influenced by the birefringence of the host crystal, the orientation of the quartz-fluid interface, and the depth of the inclusion. The variation in Peak1 due to birefringence is 3,220cm−1 to 3,239cm−1 using a polarised laser beam. Reflection polarisation caused by the orientation of the quartz-fluid interface results in a variability of 14cm−1, independently from the orientation of the indicatrix. The effect of birefringence is reduced with increasing depth.

Dynamic skew-symmetric problem of coupled thermoelasticity for a layer containing a hole

We consider a problem of coupled thermoelasticity for a layer weakened by a through hole and construct its homogeneous and F-solutions. By using these solutions, the boundary-value problem is reduced to a system of singular integral equations of the second kind. The dependence of the dynamical concentration of relative circular stresses on the first relative wave number is analyzed. The effect of coupling of the thermomechanical fields is demonstrated.

A short hydrogen bond investigation by polarized Raman spectra of Co 2+ and Zn 2+ salts of pyromellitic acid

Cobalt and zinc salts of 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), [C 6H 2(COO) 4H 4], have been synthesized and investigate by polarized Raman spectroscopy. These compounds present short intramolecular hydrogen bonds (SHB) between adjacent carboxyl groups. Raman spectra indicate the presence of this interaction in both salts. Three specific vibrational of SHB modes have been investigated: O–H–O symmetric [ ν sym(OHO)] and asymmetric [ ν asym(OHO)] stretching modes and O–H stretching mode [ ν(O–H)], which they were observed around 300, 850 and 2500 cm −1, respectively. In crystallographic point of view, the cobalt salt presents a symmetric SHB while the zinc salt presents an asymmetric SHB. In cobalt salt all three vibrational modes of O–H–O groups in polarized Raman spectra occur in A g orientation although in zinc salts two of them are observed in A g orientation and one in B g. Spectra analysis indicate that ν sym(OHO) mode is observed as A g to cobalt salt and B g to zinc salt. This mode occurs in a crowed spectral region and its identification was made by deconvolution techniques. Comparing spectra of the two salts, it is observed a small difference in relative intensity and wavenumber shift of ν sym(OHO) (deviance of 43 cm −1) and ν(OH) (deviance of 21 cm −1) modes due probably to differences in O⋯O distance between salts and in orientation of pyromellitate anion in unit cell. The ν asym(OHO) mode does not present significant wavenumber shift due difference in SHB. The ν(OH) band presents a great potential for hydrogen bond studies due to the fact that in its vibrational region (around 2500 cm −1) it is not observed other vibrational modes of these compounds.

Accurate laboratory ultraviolet wavelengths for quasar absorption-line constraints on varying fundamental constants

The most precise method of investigating possible space-time variations of the fine-structure constant, using high-redshift quasar absorption lines, is the many-multiplet (MM) method. For reliable results this method requires very accurate relative laboratory wavelengths for a number of UV resonance transitions from several different ionic species. For this purpose laboratory wavelengths and wavenumbers of 23 UV lines from MgI, MgII, TiII, CrII, MnII, FeII and ZnII have been measured using high-resolution Fourier Transform (FT) spectrometry. The spectra of the different ions (except for one FeII line, one MgI line and the TiII lines) are all measured simultaneously in the same FT spectrometry recording by using a composite hollow cathode as a light source. This decreases the relative uncertainties of all the wavelengths. In addition to any measurement uncertainty, the wavelength uncertainty is determined by that of the ArII calibration lines, by possible pressure shifts and by illumination effects. The absolute wavenumbers have uncertainties of typically 0.001 to 0.002 cm^(-1) (0.06 to 0.1 mAA at 2500 AA), while the relative wavenumbers for strong, symmetric lines in the same spectral recording have uncertainties of 0.0005 cm^(-1) (0.03 mAA at 2500 AA) or better, depending mostly on uncertainties in the line fitting procedure. This high relative precision greatly reduces the potential for systematic effects in the MM method, while the new TiII measurements now allow these transitions to be used in MM analyses.

Rayleigh Wave–Internal Wave Coupling and Internal Wave Generation above a Model Jet Stream

Abstract Linear theory for modes in a nonuniformly stratified, semi-infinite shear flow demonstrates that Rayleigh waves (stable waves propagating in fluid with spatially varying shear) couple with evanescent internal waves. If the bulk Richardson number (the squared ratio of the buoyancy frequency and shear) lies between 1/4 and 1, the waves have infinite e-folding depth for waves with critical relative horizontal wavenumbers. Fully nonlinear numerical simulations examine the effect of Rayleigh wave–internal wave coupling when the shear layer is localized and is thus Kelvin–Helmholtz unstable. Diagnostics examining profiles of the wave-induced mean flow show that if the bulk Richardson number is of order unity, significant momentum is extracted from a shear layer as a consequence of transport by waves. The work is extended to the study of unstable jet flows and applications of this work for internal wave generation by dynamic instability of the upper flank of the jet stream are discussed.

Bragg reflection of sinusoidal waves due to trapezoidal submerged breakwaters

Numerical and laboratory experiments are performed to investigate characteristics of the Bragg reflection due to multi-arrayed trapezoidal submerged breakwaters. The numerical model is based on the Reynolds averaged Navier–Stokes equations with the VOF method and the k–ε turbulence closure model. As expected, the reflection coefficients increase as the array of submerged breakwaters increases in both laboratory measurements and numerical results. The resonant periods provide similar relative wave numbers regardless of the permeability and the number of arrays. The reflection coefficients due to porous breakwaters are smaller than those due to non-porous breakwaters. The velocity contours for two and three arrays are also described.

Hyperspectral surface-enhanced Raman imaging of labeled silver nanoparticles in single cells

We describe the development of an acousto-optic tunable filter (AOTF)-based hyperspectral surface-enhanced Raman imaging (HSERI) system equipped with an intensified charged coupled device and an avalanche photodiode. The AOTF device is a miniature rapid-scanning solid-state device that has no moving parts and can be rapidly tuned (microseconds) either sequentially or randomly, over a wide spectral range between 600 and 900nm [corresponding to a large relative wave number range (∼0–4500cm−1)], with respect to a 632.8nm excitation and can also acquire images at a fairly narrow band of ∼7cm−1. In this article we describe a confocal surface-enhanced Raman imaging (SERI) system developed in our laboratory that combines hyperspectral imaging capabilities with surface-enhanced Raman scattering (SERS) to identify cellular components with high spatial and temporal resolution. The HSERI system’s application to cellular imaging is demonstrated using SERS-labeled nanoparticles in cellular systems.

A theoretical vibrational spectroscopic study with density functional theory and force field refinement calculation methods on free 4-aminopyrimidine molecule

A detailed investigation of the geometric structure, force field, electro-optical parameters, relative IR intensities and harmonic vibrational wavenumbers of free 4-aminopyrimidine molecule (4APM) in the electronically ground state has been carried out by using both the DFT-B3LYP (with 6-31++G(d,p) double and 6-311++G(d,p) triple basis sets) and force field refinement calculation methods. The vibrational wavenumbers calculated with DFT method were scaled by using two different methods: (1) scaling with dual scaling factors, (2) deriving the scaling factors from the graph of observed versus calculated wavenumbers. In the case of force field refinement method, the force constants of the pyrimidine were slightly refined so as to fit the calculated wavenumbers to the experimental ones. In order to define the contributions of the internal coordinates of the molecule on its each normal vibrational mode, P.E.D. calculations were performed. In wavenumber and PED calculations, both methods have yield results in agreement with the experimental assignment and also with each other, particularly for ring vibrations. The relative IR intensities calculated by the force field refinement method are considerably in good agreement with experimental ones, however, the results of the IR intensities, obtained from the DFT method are found to be significantly different from the experimental values.

Investigation of Wave Growth and Decay in the SWAN Model: Three Regional-Scale Applications*

Abstract Wave growth and decay characteristics in a typical wave action model [Simulating Waves Nearshore (SWAN)] are investigated in this paper. This study is motivated by generally poor agreement between model results and measurements for a regional-scale model of a two-day period during the SandyDuck '97 experiment, wherein there is consistent underprediction of lower-frequency (0.05–0.19 Hz) energy. Two separate methods are presented for improving predictions of low-frequency energy: 1) by altering the weighting of the relative wavenumber term that exists in the whitecapping formulation and 2) by disallowing the breaking of swell. The SandyDuck '97 simulation is repeated with the proposed modifications. Using the first modification, a slight improvement is seen, and with the second modification an apparent problem with nonphysical dissipation of swell by the model is corrected. The modifications are then applied to two other test cases, one in Lake Michigan and the other in the Mississippi Bight. Both...

IR and Raman spectral and X-ray structural studies of polymorphic forms of sulfamethoxazole

The crystal structure of the polymorphic form III (hemihydrate) of sulfamethoxazole (SMZ) was determined to exist in both the E- and Z-forms by X-ray analysis and was compared with the polymorphic forms I and II which are known to exist in the E-form. IR spectra of I– III and their corresponding forms I D – III D which contain the deuterated amino and amido groups and D 2O and Raman spectra of I– III have been measured. For I– III, assignment of the stretching vibration [ ν(NH) and ν(CH)] bands of amino and amido groups and the CH bond of the isoxazole ring involved in the inter-molecular hydrogen bonds has been proposed based on consideration of the IR and Raman spectra and the results of X-ray analysis. A relationship was established between the relative intensity and wavenumbers for the ν(CH) band in the inter-molecular C(sp 2)H⋯X hydrogen bond of the E-form.

Production and IR Absorption of Cyclic CS2 in Solid Ar

Linear carbon disulfide (denoted as SCS) isolated in solid N2 or Ar at 13 K was irradiated with light at 193 nm from an ArF excimer laser. In addition to an absorption line of CS at 1277.4 cm-1, new lines at 881.3 and 520.9 cm-1 were observed after photolysis of SCS in solid N2. These lines are assigned to cyclic CS2 (denoted cyc-CS2) based on results from 34S- and 13C-isotopic experiments. Doublet lines of cyc-CS2 at 876.5 (881.1) and 517.7 (522.7) cm-1 were observed after irradiation of SCS in solid Ar at 193 nm; lines in parentheses are associated with a minor matrix site. Secondary photolysis at 248, 308, 532, 560, or 580 nm diminishes signals of cyc-CS2 and produces SCS. Theoretical calculations using MP2-full and density-functional methods (BLYP and B3LYP) predict three isomers of CS2: SCS, cyc-CS2, and linear CSS; relative energies, structures, vibrational wavenumbers, and IR intensities were predicted for each isomer. Cyc-CS2 has C−S bonds (∼1.74 Å) elongated relative to those of SCS (∼1.56 Å), a S−S bond ∼2.14 Å, and ∠SCS ≈ 76°; it lies ∼73 kcal mol-1 above SCS. Calculated vibrational wavenumbers, IR intensities, and isotopic shifts for cyc-CS2 fit satisfactorily with experimental results. An asymmetric transition state connecting SCS and cyc-CS2 is characterized, yielding a ring-opening barrier of ∼24.4 kcal mol-1 (zero-point energy corrected). Photoconversion between linear and cyclic CS2 in a matrix cage is discussed.

FTIR-ATR Studies of the Hydration of 15-Crown-5 and 18-Crown-6 in Aqueous Solutions

The hydration of 15-crown-5 (15C5) and 18-crown-6 (18C6) in aqueous solutions has been studied by FTIR-ATR spectroscopy. A model of decomposition of the O−H stretching band of water into four components, accounting for bound and bulk water in the solutions, has been employed in the analysis of the spectra. The dependencies of the relative areas and peak wavenumbers of the resolved components on concentration reveal similarities and differences in the hydration of the two crown ethers. The number of water molecules influenced by the hydration is ca. 18−20 for 18C6 solutions and ca. 12−15 for 15C5 solutions at sufficiently high dilutions. The immediate hydration shell for both crown ethers consists of 4−5 water molecules directly H-bonded to the crown ring. The most probable hydration structure around 18C6 is composed of two bridging water molecules and two other water molecules singly bound to the ring, while, due to differences in its conformational structure, 15C5 is hydrated mostly by singly H-bonded water molecules.

Spectra and structure of organosphosphorus molecules. Part LX—Raman and infrared spectra, conformational stability,ab initio calculations and vibrational assignment of fluoromethyldichlorophosphine

The Raman spectra (3500–30 cm−1) of gaseous, liquid and solid and the infrared spectra (3500–400 cm−1) of gaseous and solid fluoromethyldichlorophosphine, FCH2PCl2 , were recorded. The data indicate that two conformers are present in the fluid states where the gauche conformer is the predominant species but only the trans rotamer (the F atom on the methyl group is trans to the phosphorus lone pair of non-bonded electrons) remains in the crystalline solid. The enthalpy, ΔH, was determined to be 165±8 cm −1 (472±24 cal mol−1 ); 1 cal=4.184 J with the gauche conformer more stable from the sample dissolved in liquified xenon utilizing the bands assigned to the CH2 rocks for the two conformers. Additionally, utilizing six Raman lines in the spectrum of the liquid and adjusting for their ab initio -predicted relative intensities, the enthalpy difference was determined to be 156±67 cm−1 (447±193 cal mol−1), again with the gauche conformer the more stable form. These values are in agreement with the 273 cm−1 energy difference obtained from ab initio MP2/6–311++G** calculations. Complete vibrational assignments are proposed for both conformers based on infrared band contours, Raman and infrared relative intensities and group wavenumbers, which are supported by normal coordinate calculations utilizing the force constants from ab initio MP2/6–31G* calculations. The optimized geometries, conformational stabilities, harmonic force fields, infrared intensities, Raman activities, depolarization ratios and vibrational wavenumbers are reported for both conformers from RHF/6–31G* and/or MP2/6–31G* ab initio calculations. The calculated quantities are compared with the experimentally determined values where applicable and also with some corresponding results for some similar molecules. Copyright © 1999 John Wiley & Sons, Ltd.

Computational study of the geometric and electronic structures of MN2 (M = Mo or U)

The geometric and electronic structures of singlet, triplet, quintet and septet MN2 (M = Mo or U) have been calculated using quasi-relativistic, non-local density functional theory. The distribution of the MoN2 structures over the spin states agrees well with previous theoretical data, as do the relative energies and vibrational wavenumbers of the minima. Six true minimum energy stationary point UN2 structures have been located. Whereas all of the MoN2 structures are less stable than the Mo + N2 asymptote, all of the UN2 minima are stable with respect to dissociation to metal + dinitrogen. Singlet linear NUN is found to be the most stable UN2 structure at the scalar relativistic level, and the inclusion of spin–orbit coupling does not significantly affect the NUN energy with respect to the U + N2 asymptote. The bonding in all of the UN2 structures has been analysed. The U–N2 interaction in the quintet and septet narrow angle side-on triangular geometries is a mixture of U 5f→N2 πg δ and π backbonding, with the latter component being much the more significant. U→N2 π backbonding is also found to be the principal U–N2 interaction in triplet and septet linear end-on UN2. The U–N Mulliken overlap populations are largest for the wide angle triangular and linear NUN structures, consistent with the much shorter U–N bond lengths in these geometries in comparison with the narrow angle side-on and linear end-on minima. The agreement between the calculated and experimental vibrational wavenumbers for linear NUN is very good, and is superior to previous theoretical studies. The relevance of the present work to previous computational investigations of the U–N2–U bonding in [{(NH2)3(NH3)U}2(µ-η2∶η2-N2)] is discussed.