Pressure broadening and shift in the millimeter-wave spectrum of formaldehyde

Helium, hydrogen, and self-broadening have been measured at room temperature for 12 lines of formaldehyde between 100 and 300 GHz. The self-broadening parameters ranged from 20 to 30 MHz/Torr, with typical accuracies of 0.5–0.8 MHz/Torr. For all measured lines the helium and hydrogen broadening parameters were 2.5 and 5.5 MHz/Torr, respectively, to within the experimental accuracy, typically 0.25 MHz/Torr. Pressure shifts of up to 2.5 MHz/Torr were observed in self-broadening, with estimated errors of 0.25–0.50 MHz/Torr. No significant lineshifts were seen in the foreign gas broadening measurements.The observed widths and shifts are compared with those calculated from three models of molecular collisions: Anderson's pressure broadening theory, a similar semiclassical theory of Rabitz and Gordon, and a hard-sphere, sudden approximation model of Thaddeus.     

EPR Studies of DOPA–Melanin Complexes with Netilmicin and Cu(II) at Temperatures in the Range of 105–300?K

The application of electron paramagnetic resonance (EPR) spectroscopy in pharmacy of melanin complexes with netilmicin and Cu(II) was presented. The continuous microwave saturation of EPR spectra of DOPA–melanin and the complexes was performed. EPR spectra were measured on an X-band (9.3?GHz) spectrometer at temperatures in the range of 105–300?K. Paramagnetic copper ions decrease the intensity of the EPR lines of melanin’s free radicals. It was found that fast spin–lattice relaxation characterizes DOPA–melanin–Cu(II) complexes. Slow spin–lattice relaxation processes exist in melanin’s paramagnetic centers of DOPA–melanin and DOPA–melanin–netilmicin, [DOPA–melanin–netilmicin]–Cu(II), [DOPA–melanin–Cu(II)]–netilmicin complexes. Spin–lattice relaxation processes are faster at higher temperatures. The homogeneous broadening of EPR lines for melanin complexes was observed. The practical consequences of differences between paramagnetic properties of melanin complexes with netilmicin and the complexes with Cu(II) were discussed.     

Measurements of N2−, O2−, and air-broadened linewidths of ozone in the millimeter region: Temperature dependence of the linewidths

Measurements have been made at room temperature on the widths of selected microwave lines of ozone broadened by three gases: oxygen, nitrogen, and air. For the 2_1,1 ← 2_0,2 line, the temperature dependence of the foreign-gas broadening parameters has been studied in the range 240–293 K. The results are reported along with their accuracies, and are compared with published data.     

Stability-Indicating Method for the Determination of Meloxicam and Tetracaine Hydrochloride in the Presence of their Degradation Products

Abstract

Sensitive, spectrophotometric and densitometric methdos are described for the determination of meloxicam I and tetracaine hydrochloride II in the presence of their degradation products.

Meloxicam was determined in the presence of its degradation products (5-methyl-2-aminothiazole) III and benzothiazine carboxylic acid IV by two methods. These methods are the first derivative Spectrophotometry at 338 nm and TLC densitometric method at 365nm. The methods were applicable over the concentration range of 5–20μg.m^?1 and 2–10μg with mean accuracies of 99.66±0.91% and 99.99±0.70% respectively.     

Effectiveness and Toxicity of Several DTPA Broadening Agents for Biological ESR Spectroscopy

The effectiveness of a standard ESR broadening agent, potassium trioxalatochromiate (CrOx), for use with the spin-label tempone, was compared to that of diethylenetriaminepentaacetic acid (DTPA) containing an ion (Gd, Cr, Mn, Fe) with a large magnetic moment. Signal attenuation, line broadening, toxicity, and cell membrane permeability were compared. As a broadening agent, CrOx was most effective, followed by Fe–DTPA. CrOx proved mildly toxic while Gd-DTPA and Fe–DTPA were virtually nontoxic. The human red blood cell membrane was tested for permeability to Fe– and Gd–DTPA and found to be impermeable to both. In situations where toxicity to cells is critical, the DTPA chelates, particularly Fe–DTPA, may prove an acceptable substitute for CrOx.     

Methodology for the characterisation of characteristic spectral profiles,applied to chromium Kβ

The investigation of tests of quantum electrodynamics in the X‐ray regime down to 2–20 parts per million (ppm) amplifies the need for improved characterisation of asymmetric reference sources and energies in this regime. While several transition metal characteristic energies have been defined, most are not referenced to accurate profiles or robust links to the metre via X‐ray optical interferometry. Lower intensity Kβ transitions have relatively poor accuracy – we ask how to determine Kβ transitions to an accuracy approaching those of Kα transitions. Instrumental broadening normally encountered in X‐ray experiments shifts the features of profiles used for calibration, such as peak energy, by a significant amount many times the quoted accuracies. We present a study of a methodology used recently to determine energies and profiles experimentally down to 4.5 and 2.7 ppm for Ti and V Kβ. In this study, we investigate the robustness of the methodology for a difficult data set and demonstrate that the approaches to and characterisation of the chromium Kβ spectral profile are consistent with accurate measurements in the literature down to 24 ppm. The peak energy of the chromium Kβ spectral profile is found to be 5946.68(14) eV prior to instrumental broadening. Characterisation of the spectral profile of the radiation, including the instrumental broadening, allows us to obtain an accurate and notably transferable standard. Significantly, we present a widely applicable methodology for achieving and using this standard. This approach has been used down to an accuracy of 2–5 ppm.     

Measurement of the Stark broadening parameters of some singly ionized argon lines

Half-widths of fifteen Stark broadened argon II lines have been measured in argon plasma behind the reflected shock wave produced in an electromagnetically driven “T” tube. The plasma electron density was determined by the laser interferometry at three different wavelengths, while the plasma temperature was measured from relative intensities of A II lines. Temperatures were in the range 8,500–16,500 °K; electron densities varied from 1.82 to 3.94 · 10¹⁷ cm^?3. The measured A II linewidths are compared with theoretical and other experimental results. It is shown that a) the broadening of A II lines is in good agreement with the theory, b) line broadening increases linearly with electron density, and c) the Stark broadened lines follow the dispersion profile to the distance of at least three halfwidths from the line center.     

A comparison of self broadening and shift of helium,neon and argon emission lines

Self broadening (van der Waals and resonance) and shift of Ne emission lines and van der Waals broadening and shift of He emission lines have been measured using a high pressure (0.5–3.0 atom), low current discharge. These results are compared with previous measurements in Ar and He to obtain a complete comparison of self broadening and shift of He, Ne and Ar emission lines. Oscillator strengths for the resonance transitions are obtained from the resonance broadening coefficients. The trend of the van der Waals broadening coefficients for the three noble gases is correctly predicted by a theory due to HINDMARSHet al.⁽⁴⁾ in which a Lennard-Jones potential is used in the impact theory formalism. The measured line shifts cannot be accounted for by this theory and reflect the need for more accurate quantum mechanical calculations.     

X-ray extended-range technique for precision measurement of the X-ray mass attenuation coefficient and Im(f) for copper using synchrotron radiation

We reconsider the long-standing problem of accurate measurement of atomic form factors for fundamental and applied problems. We discuss the X-ray extended-range technique for accurate measurement of the mass attenuation coefficient and the imaginary component of the atomic form factor. Novelties of this approach include the use of a synchrotron with detector normalisation, the direct calibration of dominant systematics using multiple thicknesses, and measurement over wide energy ranges with a resulting improvement of accuracies by an order of magnitude. This new technique achieves accuracies of 0.27–0.5% and reproducibility of 0.02% for attenuation of copper from 8.84 to 20 keV, compared to accuracies of 10% using atomic vapours. This precision challenges available theoretical calculations. Discrepancies of 10% between current theory and experiments can now be addressed.     

Experimental Line Parameters of the Oxygen A Band at 760 nm

To support atmospheric remote sensing applications, line positions, intensities, self- and nitrogen-broadened linewidths and their temperature dependences and pressure-induced shifts in line positions at room temperature were measured up to J' and N' = 22 for the oxygen A band at 13 122 cm(-1). Line intensities were obtained with 1% precisions and 2% absolute accuracies using absorption spectra recorded at Doppler-limited (0.02 cm(-1)) resolution with the McMath Fourier transform spectrometer (FTS) located at Kitt Peak National Observatory/National Solar Observatory in Arizona. The oxygen line positions were calibrated using near-infrared transitions of the 2-0 and 3-0 bands of CO as secondary standards. The intensities and positions of seven H(2)O lines near 13 900 cm(-1) were also remeasured to validate the FTS performance. The O(2) intensities fell within 1% of the values currently assumed for the molecular databases, but it was found that broadening coefficients and line positions should be revised for the A band of molecular oxygen. Copyright 2000 Academic Press.     

Pressure effects of argon and helium on the first diffuse series doublet of singly ionized barium

The shift and broadening of the first diffuse series doublet of Ba II in emission was observed under various relative densities of Ar (20–107) and He (35–121) at 2500°K. By comparing the present data with those of the shift of the principal series doublet from a previous paper, it is suggested that argon pressure causes a downward displacement for 6p²P and 6d²D levels and an upward one for 5d²D and 7s²S levels, with respect to the ground state of Ba II.     

High density measurements of the Stark broadened profile of the He(II)4686 Å line

The Stark broadened profile of the He(II)4686 Å line has been scanned in the electron density range of 1–3 × 10¹⁸ cm^-3. The electron temperature, as determined from the line to continuum ratio, ranged from 9.4 to 19.9 eV. The plasma which emitted the He(II)4686 Å line was created in a 60-kJ theta pinch operated with a high fill pressure (3 and 5 torr) of pure helium. Electron densities were calculated from the half-half widths of the He(II)4686 Å line using two Stark broadening theories. These electron densities are compared with the electron densities determined from the absolute value of the continuum intensity and a total sweep up compressional model. The two theoretical models predict electron densities in good agreement with the electron densities from the absolute value of the continuum intensity.     

Experimental study of Stark broadened N II lines from states of high orbital angular momentum

In this paper, we report experimental electron impact widths for six spectral lines belonging to 3d-4f transitions of singly ionized nitrogen. Line profiles were measured in a low pressure pulsed arc. An electron density in the range 5.9–7.5 × 10²²m^-3 was determined from the Stark width of the He II 4686 Å line, while electron temperatures of 28,300–32,300 K were measured using relative intensities of O II impurity lines. Comparison with semiempirical theoretical results does not resolve which coupling scheme, LS or LK, is better to describe atomic states in Stark broadening calculations of certain N II lines.     

pH effect on the physicochemical characteristics and efficiency of electroflotation extraction of low-soluble iron subgroup metal compounds from aqueous solutions

This paper reports on our study of the pH effect of solutions on the average hydrodynamic diameter (d_av) of the particles of the disperse phase and the electrokinetic potential (ζ) of the particles of low-soluble iron subgroup metals compounds using Fe(II, III), Ni(II), and Co(II) compounds as an example. The pH effect of solutions on the efficiency of the electroflotation extraction of metal ions from aqueous solutions containing these ions in individual form or in mixture was studied. The efficiency of the electroflotation extraction of the low-soluble compounds of iron subgroup metals is directly related to the particle size and electrokinetic potential of the particles, which depend on рН. The maximum degree of particle extraction α reached 97–99% at рН values characterized by the maximum hydrodynamic diameter of particles (over 20 μm for Fe(II) and Co(II) compounds and over 50 μm for Fe(III) and Ni(II) compounds) at ζ potentials of up to–10 mV for systems approximated to real wastewater. In the case of the extraction of the disperse phase of the Fe(III)–Ni(II)–Co(II) multicomponent system, the synergic effect was observed: the coextraction of metals was more complete and effective, which may be due to suppressed negative charge. In the range of рН 10–11, the degree of extraction of the Fe(III) disperse phase did not exceed 74%; in the ternary system, it reached 94%.     

He-broadening and shifting coefficients of HCl lines in the (1←0) and (2←0) infrared transitions

ABSTRACT

We report experimental results on the broadening and shifting coefficients in a large interval of J quantum numbers in the fundamental and first overtone vibration–rotation bands of the HCl molecule in mixtures with helium. Many of the values, especially for the overtone transition, are novel. The uncertainties for the isotope-averaged broadening coefficients amount to 2% on average for the fundamental and 1.5% for the overtone bands. Shifts have a typical uncertainty of 3%.     

The effectiveness of 1H decoupling in the 13C MAS NMR of paramagnetic solids: an experimental case study incorporating copper(II) amino acid complexes

The use of continuous-wave (CW) 1H decoupling has generally provided little improvement in the 13C MAS NMR spectroscopy of paramagnetic organic solids. Recent solid-state 13C NMR studies have demonstrated that at rapid magic-angle spinning rates CW decoupling can result in reductions in signal-to-noise and that 1H decoupling should be omitted when acquiring 13C MAS NMR spectra of paramagnetic solids. However, studies of the effectiveness of modern 1H decoupling sequences are lacking, and the performance of such sequences over a variety of experimental conditions must be investigated before 1H decoupling is discounted altogether. We have studied the performance of several commonly used advanced decoupling pulse sequences, namely the TPPM, SPINAL-64, XiX, and eDROOPY sequences, in 13C MAS NMR experiments performed under four combinations of the magnetic field strength (7.05 or 11.75T), rotor frequency (15 or 30kHz), and 1H rf-field strength (71, 100, or 140kHz). The effectiveness of these sequences has been evaluated by comparing the 13C signal intensity, linewidth at half-height, LWHH, and coherence lifetimes, T2('), of the methine carbon of copper(II) bis(dl-alanine) monohydrate, Cu(ala)(2).H2O, and methylene carbon of copper(II) bis(dl-2-aminobutyrate), Cu(ambut)(2), obtained with the advanced sequences to those obtained without 1H decoupling, with CW decoupling, and for fully deuterium labelled samples. The latter have been used as model compounds with perfect 1H decoupling and provide a measure of the efficiency of the 1H decoupling sequence. Overall, the effectiveness of 1H decoupling depends strongly on the decoupling sequence utilized, the experimental conditions and the sample studied. Of the decoupling sequences studied, the XiX sequence consistently yielded the best results, although any of the advanced decoupling sequences strongly outperformed the CW sequence and provided improvements over no 1H decoupling. Experiments performed at 7.05T demonstrate that the XiX decoupling sequence is the least sensitive to changes in the 1H transmitter frequency and may explain the superior performance of this decoupling sequence. Overall, the most important factor in the effectiveness of 1H decoupling was the carbon type studied, with the methylene carbon of Cu(ambut)(2) being substantially more sensitive to 1H decoupling than the methine carbon of Cu(ala)(2).H2O. An analysis of the various broadening mechanisms contributing to 13C linewidths has been performed in order to rationalize the different sensitivities of the two carbon sites under the four experimental conditions.     

Redox-Switchable New Phthalocyanines Containing Hydrazono-Thiazole-Carboxylate Fragments: Synthesis,Electrochemical, Spectroelectrochemical and Electrocolorimetric Investigation

New phthalonitrile compound with Schiff base, carbothioamide and thiazole moieties as substituents and its corresponding metal-free and metallophthalocyanines (Zn(II), Ni(II), Co(II), and Cu(II)) were synthesized and characterized for the first time. The solubilities of these novel phthalocyanines were high in organic solvents. The redox properties of the compounds have been researched by cyclic voltammetry, square wave voltammetry, controlled-potential coulometry and in situ spectroelectrochemistry in dimethylsulfoxide. The compounds displayed metal and/or phthalocyanine ring-based, generally reversible or quasi-reversible reduction and oxidation processes. The effect of aggregation on the redox behavior of these complexes was also discussed. In general, decreased intensity and broadening in the main Q absorption band and the appearance of a new blue-shifted band confirmed the presence of H-type aggregates in the solutions of the complexes 4, 6 and 8 in DMSO/TBAP. The color changes associated with the redox processes and electrogenerated anionic and cationic redox species were also recorded with in situ electrocolorimetric measurements. In situ UV–vis spectral and associated color changes monitored during the reduction processes of the complexes suggested their applicability in the fields of the electrochemical technologies.     

Spectroscopic and Conductance Studies of New Transition Metal Complexes with a Schiff Base Derived from 4‐Methoxybenzaldehyde and 1,2‐bis(p‐Aminophenoxy)ethane

Four new metal complexes of Cu(II), Ni(II), Zn(II) and Co(III) with Schiff base derived from 4‐methoxybenzaldehyde and 1,2‐bis(p‐aminophenoxy)ethane have been prepared and characterized by magnetic susceptibility, conductance measurements, elemental analyses, UV–Vis, ¹H NMR and IR spectra studies. The magnetic and spectroscopic data indicate an octahedral geometry for the six‐coordinate complexes. The ligand was used for complexation studies. Stability constants were measured by means of a conductometric method. Furthermore, the stability constants for complexation between ZnCl₂, Cu(NO₃)₂ and AgNO₃ salts and ligand (L) in 80% dioxane–water and pure methanol were determined from conductance measurements. In 80% dioxane–water, he stability constants (log Ke) increase inversely with the crystal radii in the order Ag(I) < Zn(II) < Cu(II).     

Variable-Temperature and High-Pressure Micro-Raman Spectra of Inorganic Artists' Pigments: Crystalline Wulfenite,Lead(II) Molybdate(VI), PbMoO4

Variable-temperature (?150°C to 600°C) and high-pressure (up to ～5 GPa) micro-Raman spectra have been obtained for the mineral wulfenite [lead(II) molybdate(VI), PbMoO₄], a main constituent of the artists' pigment, orange molybdate. The spectra were quite similar in both the temperature and the pressure studies, except for broadening and shifting of some peaks. No phase changes were detected, although there is possibly some amorphization beginning at ～600°C. The photoacoustic IR spectrum in the 1950–450 cm^?1 region is reported for characterization purposes. The long-term stability of PbMoO₄ with respect to extreme changes in both temperature and pressure illustrates the importance of orange molybdate in artwork and protective coatings.     

The use of positron annihilation Doppler broadening spectroscopy in the characterization of radiochromic dosimetry films

The positron annihilation Doppler broadening (PADB) spectroscopy has been employed to probe the defects and structural changes of various types of materials. In this work, an investigation was carried out for the first time to use PADB spectroscopy in probing the γ irradiated radiochromic films. The GafChromic MD–55 and HD–V2 radiochromic films irradiated with absorbed doses ranges of 0–80 and 0–2000 Gy, respectively, were subjected to Doppler broadening measurements employing a HPGe γ–ray spectrometer. The Doppler broadening line–shape parameters (S and W) of 511 keV annihilation radiations were discussed in terms of the polymerization degree of the active components of these dosimetry films. The S- and W-parameters were found to be dependent on the active component structures of both films. A reasonable correlation was also found between the values of the S–parameter and the optical density of these radiochromic films. In addition, the Doppler broadening line–shape parameters were successfully used to provide explanation of the observed nonlinearity of these films at the end of their dynamic dose ranges. The results demonstrate the applicability of the PADB technique to probe the physical and chemical changes occurred in the active layer of the studied radiochromic films during the solid–state polymerization reaction caused by γ irradiation of different absorbed doses.