Intensities of » bands

Katritzky and Topsom have reviewed the information available, largely from infrared and n.m.r. studies, concerning the distortion of the tt-electron system in the benzene ring brought about in the ground state by substituents. Of particular interest is the observation that both n.m.r. studies (of m- F and chemical shifts) and infrared investigations (of the intensities of bands due to certain skeletal vibrations) suggest that the value of Taft s [Pg.226]

Intensities of bands are symbolized VS, very strong S, strong M. medium W, weak. 

In retrospect, by inspecting the literature, we find a confirmation of this variance (see for instance Ref. [67]). Peak intensities of bands originally assigned to Franck-Condon components of the excilonic emission have random relative intensities. This would not be possible if the bands were intrinsically vibronic. Since we know that the excilonic emission, as it is observed in single crystals, is rather sharp at low temperatures, we were forced to reconsider the assignment of the fluorescence of thin films. From the temperature dependence of the fluorescence effi-... 

At RT, NH3 adsorbed on Lewis acid sites, Zr and V. Accordingly, the intensity of bands from NH3 decreased little with the V-content, by 15% at most, as expected on account of the similar Lewis acid strengths of Zr V and VV. The symmetric bending... 

The success of spectral identification depends on the appropriate reference spectra for comparison. IR measurement of eluates that are at slightly subambient temperature is advantageous considering that the large databases of condensed-state spectra may be searched. Spectra measured by matrix-isolation GC-FTIR have characteristically narrow bandwidths compared with the spectra of samples in the condensed phase near ambient temperature or in the gas phase. In addition, the relative intensities of bands in the spectra of matrix-isolated samples often change compared with either gas- or condensed-phase spectra [195]. GC-FTIR spectra obtained by direct deposition match well with the corresponding reference spectra in standard phase... 

There have been many attempts to correlate substituted aromatic species. Among the most successful have been with the I frequency of the C=0 band in (52) and (53), and with the intensity j of the 1600 cm-1 ring vibration in (54) ... 

The ATR technique is a commonly used infrared internal reflection sampling technique. It samples only the surface layer in contact with the ATR element the sampling depth probed is typically of the order of 0.3-3 pm [1]. Unless software corrected, compared with a transmission spectrum, the relative intensity of bands within an ATR spectrum increase in intensity with decreasing wavenumber. Several FTIR instrument companies now supply "ATR-correction" software developed to correct for the different relative intensities of bands observed between ATR and transmission spectra, so that ATR spectra can be more easily compared to and searched against transmission spectra. 

The dependence of intensity of the observed bands on pressure is significant. Except for a relatively small intercept the intensities of bands at about 3130 and 3060 cm-1 are roughly proportional to pressure between 22 and 240 mm, whereas the intensities of bands at 1451, 1438, 1600, and 2984 cm-1 are insensitive to pressure in this region. (The band at 2993 cm-1 seems to behave similarly to the bands above 3000 cm-1, but its overlap with the band at 2984 cm-1 makes analysis difficult.) Thus, the bands above 3000 cm-1 (and perhaps the band at 2993 cm-1) are primarily due to physically adsorbed ethylene and only in part due to chemisorbed ethylene. By way of contrast the remaining bands stem primarily from chemisorbed ethylene. 

Destruction of protein molecules. In this case one can expect a decrease in the molecular weight of components of the protein mixture, reflected in a decrease in the intensity of bands in the high-molecular zone (closer to the start) and an increase in the relative amount of low-molecular weight components (in the proximal zone of the gel). 

In order to stop the reaction when the amount of monoole-finic product in the reaction mixture is highest, aliquots of the reaction mixture are removed at intervals and analyzed by infrared spectrometry or by gas chromatography. In the infrared spectrum the relative intensities of bands at 965 cm. (trans-CH=CH) and 702 cm. (m-CH=CH) are observed in successive aliquots. The reaction is stopped when the band at 965 cm.- attributable to the trans double bonds of the starting triene, has almost completely disappeared and the band at 702 cm.- (m-olefin) remains. 

Colors and intensity of bands may differ after formaldehyde fixation compared with those obtained by glutaraldehyde fixation. Formaldehyde yields blackish and glutaraldehyde gives brownish bands. 

Several generalizations are made on the basis of such data as in Table I. For instance, the two rings tend to absorb independently of one another10 that is, no conjugation of one ring to another. Nesmeyanov has also noted that while intensities of bands in the 220-600 m region increased from ferrocene to monosubstituted ferrocenes to heteroannularly disubstituted ferrocenes, the opposite is true in the 180-220 mjx region. 

Absorption and Emission of Radiation. Raman spectra of NaNs have been detd by Petrikalns Hochberg (Ref 41), Kahovec Kohlrausch (Ref 111) and by Sheinker Syikin (Ref 120). Moler (Ref 99) expressed the absorption spectra of aq NaN3 soln as log of extinction coeff vs wave length. Sheinker (Ref 127) noted that the UV absorption spectra of aq NaNj soln were markedly different from those of typical aliphatic azides. Infrared absorption spectra were reported by Lieber et al (Ref 129) and by Delay et al (Ref 105) in the range 3 to 19ft. From the intensities of bands observed, it was concluded by Delay et al that the sym form was more abundant than the unsym form in azides of Na, Cu, Aq and Hg but the reverse was true for azides of T1 and Pb... 

Let us consider how H+M-M+ is formed, using the scheme for thermal genesis of the active sites and the spectra in Figure 1. On adsorption of Y,Y-dimethylaniline in zeolite 3 in the dark, the 540-600-nm band is observed only in the samples heat treated at 350°, 450°, and 550°C—i.e., when H+M-M+ formation is preceded by formation of both primary MH+ and M+ products. The intensity of bands shows that the most favorable conditions for H+M-M+ formation occurred after zeolite pretreatment at 550°C when the excess M+ cation radicals (430-470 nm) were found together with the H+M+-M+ product. When the samples were treated at 350° and 450°C, all M+ cation radicals reacted. 

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