Absorption spectra region

Microwave spectroscopy began in 1934 with the observation of the -20 GHz absorption spectrum of ammonia by Cleeton and Williams. Here we will consider the microwave region of the electromagnetic... 

A different example of non-adiabatic effects is found in the absorption spectrum of pyrazine [171,172]. In this spectrum, the, Si state is a weak structured band, whereas the S2 state is an intense broad, fairly featureless band. Importantly, the fluorescence lifetime is seen fo dramatically decrease in fhe energy region of the 82 band. There is thus an efficient nonradiative relaxation path from this state, which results in the broad spectrum. Again, this is due to vibronic coupling between the two states [109,173,174]. 

An obvious difficulty here is deciding the location of the broken line portions of the peaks in the region of overlap. Some features of the infrared absorption spectrum may also be analyzed by the same procedure to yield values for 6. 

Electronic transitions in molecules in supersonic jets may be investigated by intersecting the jet with a tunable dye laser in the region of molecular flow and observing the total fluorescence intensity. As the laser is tuned across the absorption band system a fluorescence excitation spectrum results which strongly resembles the absorption spectrum. The spectrum... 

In the process of inhibition polypyrocatechin borate interacts with polyethylene macroradicals to form the B—O—C bonds. This is confirmed by the fact that the absorption spectrum of polyethylene inhibited with polypyrocatechin borate revealed the bands in the region of 1350 cm" characteristic for the B—O—C bond. There is no such a band in the spectrum of pure polypyrocatechin borate after heating under the same conditions. Chemical analysis of boron in polyethylene provides support for the IR-spectroscopy data concerning the presence of chemically bonded boron in polyethylene after destruction. 

Absorption spectrum (Section 12.5) A plot of wavelength of incident light versus amount of light absorbed. Organic molecules show absorption spectra in both the infrared and the ultraviolet regions of the electromagnetic spectrum. 

From the color (absorption spectrum) of a complex ion, it is sometimes possible to deduce the value of AOJ the crystal field splitting energy. The situation is particularly simple in 22Ti3+, which contains only one 3d electron. Consider, for example, the Ti(H20)63+ ion, which has an intense purple color. This ion absorbs at 510 nm, in the green region. The... 

Spectral properties. The purified photoprotein is practically colorless, although its absorption spectrum (Fig. 7.1.4) shows a very slight absorption in the region of 330-380nm in addition to the 280 nm protein peak. The solution of photoprotein is moderately blue fluorescent, with an emission maximum at 453-455 nm and an... 

Flash photolysis of either H2S [66] or H2S2 [67, 68] in the gas phase at low partial pressures produces, inter aha, HS2- radicals which were detected by their UV absorption spectrum in the 307-380 nm region. In addition, singlet and triplet 2 molecules as well as SH radicals are formed from H2S2, and the following reaction mechanism has been proposed (photolysis in the region 200-300 nm in the presence of excess CO2) [67] ... 

The electronic spectrum of S2O has been studied both in absorption and in emission and both in the ultraviolet and the visible regions. The absorption spectrum in the near UV region is extremely intense and well suited to detect S2O in gases even at very low partial pressures. Two band systems are located in the UV region at 340-250 nm and at 230-190 nm [35] while a third system in the visible region at 645-575 nm was discovered only by op-toacoustic detection [36]. The 340-250 nm system has also been observed for matrix-isolated S2O [37]. For more details see [1, 38-47]. 

Figure 4. The calculated spectrum of the complex after a Lorentzian band convolution. Region I is dominated by bridging-sulfur-to-iron CT transitions, while region II is mostly due to organic-sulfur-to-iron electron transitions. Regions I and II are explained in a MO diagram. The vertical lines correspond to the experimental bands observed in the absorption spectrum of the [Fe2 (J. - S2) P o - CqH4S) ) ] complex, from Reference 1.

The various porphyrinogens are colorless, whereas the various porphyrins are all colored. In the smdy of porphyrins or porphyrin derivatives, the characteristic absorption spectrum that each exhibits—in both the visible and the ultraviolet regions of the spectrum—is of great value. An example is the absorption curve for a solution of porphyrin in 5% hydrochloric acid (Figure 32-10). Note particularly the sharp absorption band near 400 nm. This is a distinguishing feamre of the porphin ring and is characteristic of all porphyrins regardless of the... 

The absorption and fluorescence spectra of a neat film made of RdB-den-drimer are shown in Fig. 2. The absorption spectrum in visible-wavelength region was similar to that obtained from a solution of RdB with a concentration less than 0.1 mmol/1. Interpretation of the fluorescence in terms of the Frank-Condon mechanism indicated that the core RdB chromophore behaved with a site-isolation effect and had little interaction with the neighboring chro-... 

Figure 5. X-ray absorption spectrum of a silica supported platinum-iridium catalyst at 100 K in the region of the L absorption edges of platinum and iridium. Reproduced with permission from Ref. 13. Copyright 1982, American Institute of Physics.

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