Light atomic spectra

Knowledge on the plasma species can be obtained by the use of plasma diagnostics techniques, such as optical emission spectroscopy (OES) and mass spectroscopy (MS). Both techniques are able to probe atomic and molecular, neutral or ionized species present in plasmas. OES is based on measuring the light emission spectrum that arises from the relaxation of plasma species in excited energy states. MS, on the other hand, is generally based on the measurement of mass spectra of ground state species. 

Hi) Line Spectra Line spectra are usually encountered when the light emitting substance i.e., the radiating species are separate atomic entities (particles) which are distinctly separated from one another, as in gas. Therefore, it is invariably known as atomic spectrum . As the line spectrum depends solely upon the type of an atom, hence it enjoys the status of a predominant type of emission spectroscopy. 

To produce this type of atomic emission in a pyrotechnic system, one must produce sufficient heat to generate atomic vapor in the flame, and then excite the atoms from the ground to various possible excited electronic states. Emission intensity will increase as the flame temperature increases, as more and more atoms are vaporized and excited. Return of the atoms to their ground state produces the light emission. A pattern of wavelengths, known as an atomic spectrum, is produced by each element. This pattern - a series of lines - corresponds to the various electronic... 

Very broadly speaking, two situations have to be considered in explaining devices such as those we have mentioned. In the first, which is relevant to the ruby laser and to phosphors for fluorescent lights, the light is emitted by an impurity ion in a host lattice. We are concerned here with what is essentially an atomic spectrum modified by the lattice. In the second case, which applies to LEDs and the gallium arsenide laser, the optical properties of the delocalised electrons in the bulk solid are important. 

If every atomic spectrum were a rainbow instead of a unique pattern of light, what could be said about the locations of electrons in the atom ... 

EXAFS data on bromoperoxidase (48) point to backscattering from light atoms, which may be due to histidine coordination or the presence of a tyrosine. However, intense ligand-to-metal charge-transfer bands in the visible spectra, such as those seen in mono-oxovanadium(V) phenolates (66-69), have not been observed in bromoperoxidase (15,16, 19). Thus, the proposal (48) of a tyrosine residue coordinated to vanadi-um(V) in bromoperoxidase is not very likely. In fact, the tailing observed (15,16,19) in the absorbance spectrum of bromoperoxidase from 280 to 350 nm may be due to the absorbance of vanadate (56) incorporated in the enzyme. 

The practice of cooling discharge tubes in liquid air allowed some reduction in the Doppler width, but this technique was not always fully exploited since it was common to use high current densities in order to obtain a bright atomic spectrum. A considerable advance wras made after the discovery of deuterium in 1932, since the Doppler width of these lines compared with those of the light isotope is smaller by the factor (see Fig. 3). 

According to the Bohr model, an atomic spectrum consists of separate lines because an atom has only certain, allowable energy levels [states). The energy of the atom changes when an electron moves from one orbit to another as the atom absorbs (or emits) light of a specific frequency. 

Additional information about the structure of complex 5 was obtained from extended X-ray absorption fine structure (EXAFS) spectra. " The curve of radial distribution of atoms, RDA, which was calculated on the basis of the EXAFS spectrum of complex 5 contained only two maxima - 2.1 +0.1 A for the Pd-light atom distance and 2.6 + 0.1 A for the Pd-Pd distance. Maxima corresponding to the distances between the more remote Pd atoms were not detected. 

The principle of atomic absorption analysis (AAS) is based on the fact that atoms absorb radiation at the same wavelength at which they emit. The sample is atomized in the light path of a radiation source emitting the atomic spectrum of the analysed element, and the extent of absorbed radiation (absorbance) is proportional to the concentration of the element. 

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