Studies, spectra

Formulae—See Equations Fourier-transform spectroscopic studies, spectra of Pu-240,... 

The bottom line quantitative distance data are hard to get from dipolar interaction data, but qualitative or topological information can be obtained. It is usually helpful to study spectra from intermediate redox-titration samples and/or spectra taken at different microwave frequencies. 

The present survey of absorption edge spectra of known compounds provides a background concerning the type of information these spectra may provide in catalyst studies. Spectra emphasizing the first 30 ev. range... 

Of course, these solvents transmit through much larger regions of the spectrum than do hydrocarbons. Where both >(CO) and other modes are to be studied, spectra should if possible be obtained in the >(CO) region in alkane (for resolution) and also in the solvent chosen for the other regions (for comparison). 

The finding of this element was by no means accidental. Boisbaudran had been studying spectra for fifteen years, and had found that in... 

Benali-Baitich studied spectra of V02+-perchloric acid (0 [HC104] 13.3 M).461 For high... 

It would be of interest to study spectra from ethene adsorbed on newly reduced but relatively unannealed catalysts of other metals. The marked changes in surface sites implied in going from Fig. 10C to Fig. 10G are analogous to those expected during catalyst break-in phenomena (194). 

Mass spectroscopic studies on 1,3,2-diazaboracydoalkanes 18> seem to reveal some interesting aspects. It appears that dehydrogenation at annular carbon atoms under electron impact is readily accomplished. This observation tends to indicate that the resultant products may be stable and suggests research in this area. Moreover, it is noteworthy that in all the spectra which have been studied so far, no complete breakdown of the molecules was observed. Instead, species with one of the two original boron-nitrogen bonds left intact appear to be rather stable and there seems to be a particular tendency for the intramolecular formation of boron-containing species with one B—N and at least one B—C bond. Also, a characteristic breakdown pattern in all of the studied spectra of 1,3,2-diazaboracycloalkanes seems to be established inasmuch as the ready loss of exocyclic groups other than those attached to the boron atom has been observed. 

FTIR spectroscopy to a particular pesticide, the methods have general applications to numerous compounds. Most of these utilize the high sensitivity of FTIR, and the data manipulation capability of the system. In several of the gas evolution studies, spectra were acquired at less than one-minute intervals. While this is not really "rapid scanning," the high resolution required for vapor phase spectra would not have been possible with a normal dispersive instrument. Several other techniques using FTIR show promise in the area of pesticide analysis. 

Absorption spectra of Pr(M) and Nd(III) complexes with alkyl, aryl, fluorine substituted P-diketones and the associated hypersensitive transitions were studied in detail. Mono, bis, tris and tetrakis complexes in benzene, DMF, DMSO and ethanol were also studied. Spectra both in solids and solution permitted the interpretation of the state of p-diketones based on the trends in the intensity and energy interaction parameters [238,244]. The various complexes were isolated and their IR, 1H NMR, stability constants were studied as well. Octacoordination in the tetrakis complex and tris complex associated with two solvent molecules was noted. 

Aromatic hydrocarbons Model studies spectra of detergent-solubilized aromatic hydrocarbons Riegelman et al. (1968)... 

In all of these previous spectroscopic studies spectra were not recorded under reaction conditions. With a reaction sequence as complex as that in MTG spectra recorded at room temperature after heating the zeolite in the presence of methanol are likely to contain contributions from strongly adsorbed reaction products which may obscure the species initially formed. Although these contributions can be minimized by high temperature desorption prior to measuring spectra, this may also perturb the adsorbed species formed initially. 

This is one of the best characterized systems to date ° In these studies, spectra were obtained by monitoring the characteristic CuK, fluorescence intensity at 8.04 KeV. Spectra were obtained with the polarization of the x-ray beam being either perpendicular (Fig. 15A) or parallel (Fig. 15B) to the plane of the electrode. In both cases, a number of well-defined oscillations were observed in addition to a sharply defined edge. From a qualitative... 

Considering the result, a straight line or a curve, the studied spectra can have the same shape (homothetic) or be very different. Depending of the curve type, information... 

In several cases, spectra normalisation is a preliminary step to a further study [1], This operation leads to give a same area (arbitrarily chosen) under the studied spectra. Considering that UV spectra of aqueous samples are often related to dilution phenomena, the normalisation step tries to prevent this effect. In practice, the area of spectra is given by the sum of absorbances between two given wavelengths (e.g. 200 and 350 nm). More generally, if the absorbance values are acquired every h nanometres, the area can be calculated by ... 

Dilation of bands under the wave influence has also been observed for the region 1000-1300 cm"1 where there are bands of skeletal vibrations of chains -C-C-C- and CH2- and CH3-groups, as well as vibrations of aromatic systems. Interesting feature of the studied spectra is a decrease of the intensity of bands at 910 cm1, 967 cm1, 1640 cm1, 1660 cm"1 and occurrence after vibrating influence of bands at 3440 cm1 and 3238 cm"1, which intensity increases with increase of time and frequency of treatment. These bands belong to vibrations of O-H bond in water and hydroxylic compounds. 

Benali-Baitich studied spectra of VO -perchloric acid (0 [HCIO4] < 13.3 M). For high acid concentrations, is oxidized others observed rapid oxidation in solutions containing 2.2M NaC104 for pH5= 2.5. From the visible spectra, CIOJ coordinates. However, such changes may arise from VOH" (see Section 33.5.5.1.i), not CIOJ coordination. ... 

When studying spectra of solutions one should be aware that interactions between solute and solvent have effects on band position and intensity, but it seems preferable to put up with the relatively mild interactions between solute and nonpolar solvent than to try to identify frequencies from the much stronger interactions between adjacent polar molecules in a pure liquid or the even stronger interactions between juxtaposed molecules in a crystal lattice. Moreover, in a pure nonpolar liquid the interactions of adjacent molecules are just as important as interactions between these molecules and nonpolar molecules of solvent in a dilute solution. 

The practice of analytical spectroscopy preceded the development of the theories concerning the origin of spectra by a number of years. Bunsen and Kirchhoff studied spectra produced by salts and salt solutions heated in flames and noted the characteristic spectral line emissions of a number of elements. They also observed that substances absorb energy most strongly at the same wavelengths at which emission occurs. Their results led Kirchhoff to state that the power of emission is equal to the power of absorption for all... 

There are a number of factors that may complicate the interpretation of infrared spectra. These factors should be considered when studying spectra as they can result in important changes to the spectra and may result in the misinterpretation... 

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