Journal of Applied Spectroscopy最新文献

Spectroscopy of a mixture of atomic cesium (Cs) and molecular nitrogen (N₂) gas in a nanocell was studied for the first time. An optical nanocell of thickness L ~ 800 nm was used to measure the broadening and shift of the Cs-atom D₂ line by gaseous nitrogen N₂ at a pressure of 400 Torr. The absorption spectra of pure cesium vapor and cesium vapor with the addition of gaseous nitrogen were measured. The measured values of the shift and broadening of the Cs D₂ lines in the presence of N₂ were –7 ± 1 and 15 ± 0.7 MHz/Torr. The results were in good agreement with the values given in the literature.

Green synthesis techniques have gained much attention, as they serve as an environmentally friendly substitute for the synthesis of nanoparticles. Here, we present a cheap, energy-efficient, and eco-friendly approach to producing magnesium oxide nanoparticles (MgONPs) utilizing maize leaves as a bio-reducing agent. This method reduces the effects of traditional chemical-based synthesis, by utilizing the reducing characteristics of maize leaves to promote the synthesis in a sustainable way. Using various analytical tools such as UV-Visible, XRD, FE-SEM, and FTIR, we thoroughly characterized the synthesized nanoparticles. Biogenic MgONPs are of spherical morphology, and the size ranges from 40 to 100 nm, reflecting their multifunctionality. This work highlights the synthesis of maizemediated MgONPs as a viable strategy for the environmentally friendly and sustainable synthesis of nanoparticles.

The experimental dependence of the transparency current of InGaAs/GaAs quantum well-dots on the photon energy, which corresponds to the difference of quasi-Fermi levels for electrons and holes, has been obtained. It is shown that modal gain spectra can be calculated from spontaneous luminescence spectra using the obtained dependence and the known relationship between spontaneous luminescence and optical absorption. Modal gain spectra of InGaAs/GaAs quantum well-dots at different pump currents have been calculated. The technique can be used to study gain spectra of devices operating in superluminescence regimes, when the position of the gain maximum is unknown.

LiSr_1–xPb_xBO₃ (x = 0, 0.0025, and 0.005) materials were synthesized at 750°C for 6 h in air. Powder X-ray diffraction and FTIR were used to determine the phase and bond structure of the synthesized LiSrBO₃. Spectrofl uorometry was used to investigate the photoluminescence properties of the prepared phosphors at room temperature. LiSrBO₃:Pb²⁺ was found to have emission and excitation bands at 362 and 275 nm, respectively. Finally, the prepared material LiSrBO₃:Pb²⁺ was found to have a Stokes shift of 8739 cm^–1, using the excitation band at 275 nm and the emission band at 362 nm. As a result of this work, a new UVA radiation-emitting substance has been introduced to the literature.

The photoluminescence (PL) spectra, PL excitation spectra (PLES), and PL kinetics of micropowders of CaGa₂S₄:3%Nd,5%Yb and CaGa₂S₄:3%Nd compounds at room temperature were studied in a broad range of optical excitation levels. In the PL spectra and PLES, the transition bands of the Nd³⁺ ions in the wavelength range 300–1500 nm were identified. Doping of the CaGa₂S₄:3%Nd crystals with ytterbium ions leads to the appearance of an intense violet-green band with maximum at 488 nm in the PLES. When excited within this band, the PL intensities in the IR bands of neodymium are increased by two orders of magnitude but when excited outside this band, the enhancement is only by one order of magnitude compared to the analogous PL intensities of the undoped crystal. Experimental decay of PL is observed upon excitation to the Nd absorption bands. An initial rise in photoluminescence is observed upon excitation to the broad band arising upon doping of CaGa₂S₄:Nd with ytterbium followed by exponential decay. The major features of the PL decay kinetics in CaGa₂S₄:3%Nd,5%Yb were interpreted in the framework of a mathematical model for nonradiative energy transfer (Förster Resonance Energy Transfer, FRET).

The effect of laser radiation on the formation of fi lm-like deposits on the surface of optical parts located in closed volumes containing sealants such as VGO-1, KLT-30, U-2-28, and K-68 has been studied. X-ray photoelectron spectroscopy and IR spectroscopy were used to determine the composition of the fi lm-like deposits. The composition of the gas medium was determined by mass spectrometry. The formation kinetics of fi lm-like deposits were investigated as a function of the medium temperature and the laser radiation parameters. Possible formation mechanisms of the fi lm-like deposits and methods for their elimination were considered.

Thermo-optic coefficients of monoclinic KYb_xY_1–x(WO₄)₂ crystals (x = 0, 0.05, 0.1, 0.2, 0.5, and 1.0) for E//N_p, E//N_m, and E//N_g light polarizations at wavelength 1.06 μm using the laser beam deflection technique for a medium with a linear temperature gradient. KYb_xY_1–x(WO₄)₂ crystals were grown by a modified Czochralski method using a dynamic growth regime and selection of the required temperature gradient at the crystallization front. The dn/dT coefficients obtained for all the polarizations are negative and their absolute values decrease with increasing coefficient x. The dni/dT coefficients (i = p, m, g) for KYb_xY_1–x(WO₄)₂ crystals were shown to depend linearly on their stoichiometry coefficient x.

Nanostructured thin films on silicon substrate were obtained by high-frequency pulse-periodic (f ~ 13 kHz) action of laser radiation with a wavelength of 1.064 μm and a power density of q = 64 MW/cm² on yttrium vanadate YVO₄ ceramics at a vacuum chamber pressure of p = 3 Pa. The morphology of thin YVO₄ films was studied using atomic force microscopy. Transmittance spectra of YVO₄ films were obtained in the visible, near, and mid-IR regions. The electrophysical characteristics of YVO₄/Si structures were analyzed.

High-frequency (HF) plasma ignition in commercial lamps (frequency 3 MHz, current 100 A) for 150–500 μs after its HF (2 MHz) excitation provides a selective decrease in the radiation intensity in the 400–700 nm band compared to lamp pumping by a capacitor discharge. It was found that the coefficient of the decrease in radiation intensity increased with shortening of the HF excitation duration. In addition, an increase in the intensity of the krypton atomic lines (587, 760, and 810 nm) was found in the emission spectrum of the DKRTV-3000 lamp. These lines matched the absorption bands of Nd³⁺ ions in the spectrum of the Nd³⁺:YAG laser crystal. Therefore, HF ignition was considered as an alternative to diode pumping for increasing the laser efficiency.

The effect of the structural layer thickness on the absorption peak intensity and bandwidth in optical absorption spectra of Si₃N₄/Me/Si₃N₄ structures calculated by the finite differences in time domain method was found. The absorption increased by ~20% and the absorption band with an intensity of >90% broadened from 0.8 to 1.6 μm if the total thickness of the upper and lower layers of Si₃N₄ was reduced from 400 to 100 nm. It was shown that the width of the absorption band with an intensity of >90% was 4.3 μm in the absorption spectrum of an Si₃N₄/Ti/Si₃N₄ structure with a thickness of 50 nm for each layer. The maximum absorption decreased insignificantly from 99 to 96% if the thickness of the profiled Ti layer was reduced from 130 to 50 nm. It was shown that the absorption band broadening was associated with the effect of the Si₃N₄ thickness on interference processes in the Si₃N₄/Ti/Si₃N₄ structures. It was established that the absorption level in the range 8.3–13 μm depended on the metal type because of the dependence of the free-electron concentration on the metal type.