Journal of Applied Spectroscopy最新文献

Features of Doppler-free resonances formed during scanning of Cs-atom 6S_1/2 → 7P_3/2 transitions at 456 nm in a micrometer cell are presented. The saturated absorption technique in a cell with a thickness of L = 40 μm was used. The oscillator strength of these transitions is 60 times weaker than for Cs 6S_1/2 → 6P_3/2 transitions at 852 nm. The Doppler-free resonances have a spectral line width of <20 MHz, which is 38 times smaller than the Doppler line width of 750 MHz at 120°C. These narrow resonances are of interest for both high-resolution spectroscopy and instrumentation, in particular, the creation of compact frequency references in the blue region.

Results are given for a complex study of thin Nb₂O₅ films deposited in vacuum (p = 2.2 Pa) on quartz and silicon substrates using multi-pulse high-frequency laser action (f ~ 10–12 kHz) on a ceramic target with laser power density q = 81 MW/cm². The morphology of these films was studied using atomic force microscopy. Features of the transmission spectra were presented. The photoelectrical properties of the Nb₂O₅/Si structure were analyzed.

IR spectroscopy along with x-ray diffraction and electron microscopy was used to show that the mechanochemical activation of a mixture of Degussa 25 TiO₂ and orthorhombic MoO₃ permits us to grow a disordered MoO₃ shell over titanium dioxide cores. The core–shell structure of the resultant photocatalyst particles facilitates charge separation under actinic irradiation and the accumulation of charge as reduced molybdenum oxide.

A UV visible spectroscopic method has been developed for the simultaneous estimation of quercetin and ellagic acid in a suspension. Validation of the developed method was done according to ICH Q2R2 guidelines. Calibration curves (R² > 0.98) were prepared, demonstrating a linear response for the concentration ranges of both drugs. The results indicated high levels of accuracy and precision (all %RSD values <2%). The findings suggest that this method can be readily adopted in routine laboratory settings, facilitating the simultaneous monitoring of drug levels in both bulk and dosage forms.

The current study aims to evaluate and assess the physiochemical characteristics of metformin hydrochloride, which is commonly used to treat type II diabetes. This study also focuses on the method development and validation of metformin hydrochloride by the UV-spectrophotometric method. The validation procedure adhered to the protocols specified by the ICH guidelines. The spectroscopic studies were done using simulated phosphate salivary fluid as a solvent, which mimics the physiological fluid in the human oral cavity. The drug was evaluated for its organoleptic assessment, solubility, pH, FTIR spectroscopy, partition coefficient, melting point, moisture content, and flow properties. The preformulation characteristics were thoroughly assessed and evaluated with the ranges specified in the monograph, and it was found to be within the limits. The absorption maxima for the drug using a simulated salivary fluid of pH 6.8 were found to be 233 nm, and the calibration curve for the metformin exhibited a linearity range of 1–9 μg/mL (r² = 0.998). The recovery studies were done at three different concentration levels and were found to be in the range of 97–98.8%. This study evaluates how the developed method meets its criteria for specificity, linearity, and accuracy, within the predefined acceptance limits. Thus, a simple, accurate, and economical method is developed and validated along with the preformulation characteristics, which expands its utility in the formulation of the drug.

Sub-Doppler fluorescence resonances at the central frequencies of atomic (molecular) transitions induced by stationary broadband optical pumping in a cylindrical cell with a rarefied gas medium are established and analyzed. The pump radiation is considered to propagate transversely through a relatively narrow region of this cell. The dependences of the established sub-Doppler resonances on the intensity and spatial distribution of such an optical pumping are analyzed. The proposed method of high-resolution spectroscopy allows one to reduce the Doppler broadening of the recorded fluorescence resonances by a value equal to the ratio of the gas-cell diameter to the relatively narrow width of the local region of the pumping radiation.

An interpretation of known experimental data on magnetic resonance measurements in tellurium-doped n-type indium antimonide crystals with compensation ratio K ≈ 0.1 of tellurium (hydrogen-like donors) by zinc (hydrogenlike acceptors) at 10 MHz frequency in a quantizing external magnetic field with induction from 0.17 to 1.70 T at liquid-helium temperature is proposed. It is revealed that the observed resonance is caused by the absorption of energy quanta of radio-frequency (10 MHz) radiation by c-band electrons. The electron transition between adjacent Landau levels is mediated by the electric component of the radio wave, while transitions between Zeeman sublevels are driven by its magnetic component. The number of absorbed radio-frequency quanta at resonance increases from 3.9∙10⁴ to 1.6∙10⁵ with c-band electron concentrations from 6∙10¹⁵ to 5∙10¹⁸ cm^–3 at an approximately constant compensation ratio. Calculations show that the width of the magnetic resonance lines (from peak to peak of the first derivative of the radio-wave absorption signal with respect to the external magnetic field) is determined by fluctuations in the potential energy of electrons in the crystals due to their doping and compensation.

A systematic investigation of the beam-induced surface decomposition of a typical trihalide ionic liquid, 1-octyl-3-methylimidazolium tribromide, was conducted by X-ray photoelectron spectroscopy, and the electronic environment of the bromine region is discussed. The newly formed component was assigned to bromide, based on the measured Br 3d binding energy. The atomic loss of bromine as a function of exposure time under the X-ray beam is analyzed in detail. The analysis suggests that 1-octyl-3-methylimidazolium tribromide is decomposed under X-ray beam irradiation to yield 1-octyl-3-methylimidazolium bromide and liquid bromine, the latter of which subsequently leaves the system under the ultrahigh vacuum conditions.

Tetracycline HCl and tinidazole combination drugs are used for antimicrobial therapy. In order to quantify them in dosage forms by UV spectroscopy, resolving the spectral overlap is necessary to avoid interference. The present study introduced four simple, sustainable, mathematically processed UV spectrophotometric methods for the simultaneous determination of tetracycline HCl and tinidazole in binary mixtures and tablet dosage forms. The approaches used for resolving spectral overlap include first derivative, area under curve, dual wave length, and ratio difference methods. The methods demonstrated linearity in the range of 10–40 μg/mL for both drugs, while detection limits were in the range of 1.562–2.974 μg/mL for tetracycline HCl and tinidazole showed 0.077–1.65 μg/mL. ANOVA results showed no statistical difference among the methods. Sustainability assessment made by MoGAPI, RGB, and BAGI declared the developed method to be sustainable and eco-friendly. In silico drug–drug interaction study with respect to CYP450 enzymes showed no drug interactions. The developed method showed good agreement with validation parameters and was found to be efficient, economical, free of toxic solvents, and the complex sample preparation procedures indicated its sustainability.

Magnetic nanocomposite particles of Fe₃O₄/α-FeOOH were synthesized by alkaline coprecipitation from aqueous solutions of di- and trivalent iron salts. The phase composition and magnetic characteristics of the nanocomposite particles as compared to nanoparticles of single-phase Fe₃O₄ were studied using x-ray structural analysis, Mössbauer spectroscopy, and vibration magnetometry. The sizes of the obtained particles (average diameters of 4-21 nm) and the Debye temperatures Θ_D = 273 ± 19 and 327 ± 45 K for Fe₃O₄ and Fe₃O₄/FeOOH, respectively, were determined by various methods. The obtained magnetic characteristics of Fe₃O₄/FeOOH (M_s ≈ 32 emu/g at T = 300 K) allowed this composite material to be used as a reagent in improved oxidation processes followed by magnetic decantation.