Ultra-violet and visible absorption

S. O Keeffe, C. Eitzpatrick, E. Lewis, An optical fibre based ultra violet and visible absorption spectroscopy system for ozone concentration monitoring. Sens. Actuators B, 125, 372-378 (2007). 

However, Field, W. G. Gamer and Smith [138] had concluded earlier that proton transfers do not occur in liquid ammonia solutions of m- dinitrobenzene. On the basis of ultra-violet and visible absorption spectra and electrical conductance measurements of the products of interaction of polynitroaromatic compounds with a variety of amines, Miller and Wynne-Jones [139] came to the conclusion that ... 

The ultra-violet and visible absorption spectra of irradiated alkali halides were first studied by Pohl21, who observed an intense band between 400 and 800 m/x. The centres responsible for this absorption were called F-centres and the band F-band. The fact that only one band was observed in the absorption range indicated that only one electron was involved in the transition. 

Hersfienson, H. M., Ultra-violet and Visible Absorption Spectra, Index for 1930-1954, Academic Press, New York, 1954. 

Hearn, A. G. The absorption of ozone in the ultra-violet and visible regions of the spectrum. Proc. Phys. Soc. (London) 78 932-940, 1%1. 

Emission and absorption spectroscopy give the same information about enei level separations but practical considerations generally determine which technique is employed. Absorption of ultra violet and visible light is chiefly caused by electronic excitation, the spectrum provides limited information about the structure of the molecule. In order to obtain useful information from UV and visible range spectrum of a compound the wavelength of maximum absorption and the intensity of absorption must be measured accurately. The mechanics... 

It may be generalized at this point that the absorption bands of almost all organic molecules normally found in the near ultra-violet and visible regions arise from either tt -> tt or n -> 77 transitions. The 77 77 transitions may... 

Ultra-violet and visible spectrophotometry can be effectively used for the control of purification and specification of purity of compounds. If a compound is transparent in the near ultra-violet and the visible regions, the purification is continued until the absorbancy is reduced to a minimum (e < 1). Traces of impurities present in pure transparent organic compounds can be readily detected and estimated, provided the impurities themselves have fairly intense, absorption bands. Before a liquid is used as a spectroscopic solvent, it should be tested for spectrophotometric purity. For example, commercial absolute alcohol usually contains benzene as impurity. The absence of benzene in the Alcohol should be confirmed spectrophoto-metrically by using sufficiently large cells (4 or 10 cm cells), before using the alcohol as a solvent. The presence of carbon disulphide in carbon tetrachloride may be detected by the presence of the disulphide absorption tend at 318 mytt. The detection of the characteristic benzenoid absorption in the spectra of many organic compounds (e.g. diethyl ether, cyclohexene) showed that the bands attributed to these compounds earlier were only due to the contamination by benzene1. 

ULTRA-VIOLET AND VISIBLE SPECTROSCOPY Absorption Spectra of Alkali Halides... 

Identification of organic compounds by their absorption spectra has become a routine procedure for the past several years. It is a standard practice now , to record either the infra-red or the ultra-violet spectrum while proposing a structure for a new compound or while reporting its physical properties. Electronic absorption spectroscopy has been used as confirmatory evidence for the identity of a previously known substance, just as any other physical property (e.g., melting point, refractive index). Many examples may be cited where a particular structure of a compound was selected from several possibilities on the basis of its ultra-violet or visible spectrum. The high intensity of many of the absorption bands in the near ultra-violet and visible regions not only permits the identification with minute quantities of material, but also serves as an aid in the control of purification of substances. In this book, an attempt has been made to present the basic concepts of electronic spectroscopy and to survey its analytical and structural applications in the different branches of chemistry. 

J. R. Edisbury (1967). Practical Hints on Absorption Spectrometry (Ultra-Violet and Visible). Plenum, New Y ork. 

The characteristic absorption and emission spectra of lanthanide compounds in the visible, near ultra-violet and infra-red is attributed to transitions between 4/ levels due to the fact that they present a sharp line with oscillators strengths typically of the order of 10 . These transitions are electric dipole forbidden but became allowed as forced electric dipole transitions. 

The narrow absorption and emission bands of rare-earth 0-diketonates in the visible, near ultra-violet and near infra-red is attributed to 4f-4f transitions. These transitions are electric dipole forbidden to first order, but are allowed by the electric quadrupole, vibronic, magnetic dipole and forced electric dipole mechanisms. The magnetic dipole character of the Dq F transition of the Eu + ion was demonstrated in 1939 by... 

Absorption spectra in the infta-red, emission spectra in the visible and ultra-violet and Raman-spectra together provide the most important... 

The band spectrum of chlorine in the visible and near ultra-violet is well known from the work of Kuhn8 and others. Absorption from at least the first five vibrational levels of the normal molecule is observable. One can say from which particular vibrational levels the absorption of chlorine in the above regions at ordinary temperatures originates, and the energy of these levels is known. This is sufficient to determine the temperature coefficient of such absorption. Indeed it is partly by a process the reverse of this that the allocation of absorption to the various vibrational levels is accomplished. And so from the positions of the four... 

The absorption spectroscopy has been widely used for monitoring the rate of chemical reactions. During the reaction, if there is either appearance of colour in a colourless solution or disappearance of colour in a coloured solution or a species which absorbed at a specific wavelength is formed, the spectroscopic technique can be used. Instruments like colorimeters and spectrophotometers are available to cover the visible, near infrared and ultra violet region of the spectrum (200-1000 nm). The absorption spectroscopy is governed by well-known Beer-Lambert s Law according to which ... 

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