Spectra of solids

Cl2C = CCl CCl =CCl2. Colourless viscous liquid b.p. 210-211 C. Principally used as a dispersant material for obtaining i.r. spectra of solids in mulls. Skin irritant. 

Both UPS and XPS of solids are useful techniques. So far as studies of adsorption by surfaces are concerned we would expect UPS, involving only valence orbitals, to be more sensitive. For example, if we wish to determine whether nitrogen molecules are adsorbed onto an iron surface with the axis of the molecule perpendicular or parallel to the surface it would seem that the valence orbitals would be most affected. This is generally the case but, because ultraviolet photoelectron spectra of solids are considerably broadened, it is the X-ray photoelectron spectra that are usually the most informative. 

A solvent free, fast and environmentally friendly near infrared-based methodology was developed for the determination and quality control of 11 pesticides in commercially available formulations. This methodology was based on the direct measurement of the diffuse reflectance spectra of solid samples inside glass vials and a multivariate calibration model to determine the active principle concentration in agrochemicals. The proposed PLS model was made using 11 known commercial and 22 doped samples (11 under and 11 over dosed) for calibration and 22 different formulations as the validation set. For Buprofezin, Chlorsulfuron, Cyromazine, Daminozide, Diuron and Iprodione determination, the information in the spectral range between 1618 and 2630 nm of the reflectance spectra was employed. On the other hand, for Bensulfuron, Fenoxycarb, Metalaxyl, Procymidone and Tricyclazole determination, the first order derivative spectra in the range between 1618 and 2630 nm was used. In both cases, a linear remove correction was applied. Mean accuracy errors between 0.5 and 3.1% were obtained for the validation set. 

These aspects of the optical spectra of solids are illustrated in the upper portion of Figure 1, which displays the reflectance curve (R) at room temperature for a typical semiconductor, GaAs. The fundamental absorption edge around 1.4 eV produces only a weak shoulder. Some structure is apparent in the two features around 3 eV and the large, broad peak near 5 eV. However, the dominant aspect of the line shape is the slowly varyii background. The derivative namre of Modulation Spectroscopy suppresses the uninteresting background effects in favor of sharp, deriva-... 

Fig. 12. Fluorescence spectra of DPAcN in solution (1) and in solid phase (2). Spectra of solid-phase DPAcN (5 % double bonds) were taken from the powder placed between two quartz plates, cxcitation 324 nm...

Table 1. 13-C chemical shifts (relative to TMS) from CP/MAS NMR spectra of solid cellulose polymorphs Ref.15>...

The problems involved in the study of humic substances are, as expected, also encountered in the case of fossil fuels. Most C-13 CP/MAS spectra of solid fossil fuels (coals, oil shales) do not exhibit a high level of spectral resolution50,51). They consist essentially of two broad bands — one in the aromatic/olefinic region from about 170 ppm to 95 ppm and one in the aliphatic region from about 90 to —5 ppm relative to TMS. On the other hand, lignite, an imperfectly formed coal, shows a considerable amount of fine structure. 

Fig. 9. Observed and calculated spin alignment spectra of solid HMT showing the influence of the tetrahedral jump motion for long mixing times t2 > rc. Note the strong influence of the evolution time r, on the line shape...

Nuclear y-ray resonance spectra of solid solutions of Fe and Co in /3-rh boron give inconclusive results, although the large isomer shifts as compared to Fe metal indicate that the accommodation of Fe atoms in the boron structure is associated with changes in the electronic state. The magnitudes of the shifts are... 

Cyc/o-Undecasulfur Su was first prepared in 1982 and vibrational spectra served to identify this orthorhombic allotrope as a new phase of elemental sulfur [160]. Later, the molecular and crystal structures were determined by X-ray diffraction [161, 162]. The Sn molecules are of C2 symmetry but occupy sites of Cl symmetry. The vibrational spectra show signals for the SS stretching modes between 410 and 480 cm and the bending, torsion and lattice vibrations below 290 cm [160, 162]. For a detailed list of wavenumbers, see [160]. The vibrational spectra of solid Sn are shown in Fig. 23. 

Fig. 24 Raman spectra of solid S12 (bottom) and of Si2-CS2 (top) at -80 °C. The weak line at 651 cm (with isotopic satellite) originates from CS2 [79]...

Fig. 35 K-edge XANES spectra of solid 85, Sg, Sio, Sn, S14 and polymeric sulfur normalized at 2482 eV. Figure kindly provided by A. Prange [222]...

The Raman spectra of solid a- and PS O show characteristic differences but both spectra can be assigned assuming a chair-like six-membered homocycle with an exocyclic oxygen atom (molecular symmetry Cj see Scheme 4). 

P. A. Keifer 1998, (New methods for obtaining high resolution NMR spectra of solid-phase-synthesis resins, natural products, and solution-state combinatorial chemistry libraries), Drugs Future 23, 301-307. 

Carbon-13. The molecular structure of phosphino-thioformamides (27) and their chalcogenides have been studied in the solid and liquid states.57 The, 3C n.m.r. spectra of solid methylphenyl phosphonium salts have been studied using high power decoupling cross-polarisation and slow magic angle rotation. 

We have referred to the various interactions which can cause line broadening in the solid state. One of these, which is normally not a problem in liquid state NMR, is due to the fact that the chemical shift itself is a tensor, i.e. in a coordinate system with orthogonal axes x, y and z its values along these axes can be very different. This anisotropy of the chemical shift is proportional to the magnetic field of the spectrometer (one reason why ultra-high field spectrometers are not so useful), and can lead in solid state spectra to the presence of a series of spinning sidebands, as shown in the spectra of solid polycrystalline powdered triphenylphosphine which follows (Fig. 49). In the absence of spinning, the linewidth of this sample would be around 75 ppm ... 

The relative concentration of the various butadiene microstructures, (1,4 cis, 1,4 trans, and 1,2 vinyl), were determined from the infrared spectra of solid films cast on KC1.(26) The 1,2 microstructure content of all the polymers considered in this paper were between 5-8 mole percent as determined from the IR spectra. Number average and the weight average molecular weight of the polymers were obtained via osmotic pressure and HPLC. The molecular weight of all polymers is around 200,000 g/mole while the polydispersities were about 1.1 thus, all of these polymers have a relatively narrow molecular weight distribution. Note, that both the precursor diene blocks and hydrogenated copolymers... 

Spectra of solid samples, however, consist of broad lines and are less easily interpreted. 

---