نتایج جستجو برای: atomic absorption spectra
تعداد نتایج: 302382 فیلتر نتایج به سال:
Reflectance spectroscopy is a fast and safe method to predict soil physicochemical and biological properties in low cost ways. Traditional methods to determine soil properties require spending a lot of time and money so that farmers are generally reluctant to use the results of laboratory measurements in soil and water management. Reflectance spectroscopy in the spectral range of 400-2500 nm (V...
The first application of atomic absorption spectra to chemical analysis was made as long ago as 1860 by Gustav Robert Kirchhoff (1824-87), who demonstrated the presence of various elements in the solar atmosphere. Together with Robert Wilhelm Bunsen (181199), he showed shortly afterwards that atomic spectra, whether in emission or absorption, could be the basis of a powerful method of chemical ...
background: nickel is an important constituents widely used in different industrial processes for production of various syn¬thetic materials. for evaluation of workers’ exposure to trace toxic metal of ni (ii), environmental and biological monitor¬ing are essential processes, in which, preparation of samples is one of the most time-consuming and error-prone as¬pects prior to analysis. methods: ...
We report a simple technique that allows obtaining mid-infrared absorption spectra with nanoscale spatial resolution under low-power illumination from tunable quantum cascade lasers. Light absorption is detected by measuring associated sample thermal expansion with an atomic force microscope. To detect minute thermal expansion we tune the repetition frequency of laser pulses in resonance with t...
The oligomeric hypothesis is supported by Atomic Force Microscopy (AFM) characterizations of synthetic eumelanins, formed by auto-oxidation or electrochemical oxidation of dihydroxyindole (DHI). Comparison of calculated absorption spectra to experimental spectra demonstrates a red shift in absorption with oxidation and stacking of the eumelanin, and validates the theoretical results. The work w...
The rapidly growing ultrafast science with X-ray lasers unveils atomic scale processes with unprecedented time resolution bringing the so called "molecular movie" within reach. X-ray absorption spectroscopy is one of the most powerful x-ray techniques providing both local atomic order and electronic structure when coupled with ad-hoc theory. Collecting absorption spectra within few x-ray pulses...
AA-stacked graphite shows strong anisotropy in geometric structures and velocity matrix elements. However, the absorption spectra are isotropic for the polarization vector on the graphene plane. The spectra exhibit one prominent plateau at middle energy and one shoulder structure at lower energy. These structures directly reflect the unique geometric and band structures and provide sufficient i...
We investigate the importance of the pseudo-continuum bound-free opacity from hydrogen atoms in the atmospheres of cool white dwarfs. This source of absorption, when calculated by the occupation probability formalism applied in the modeling of white dwarf atmospheres with Teff < 17000K, dominates all other sources of opacity at optical wavelengths. This is unrealistic and not observed. On the o...
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