Raman-spectra

Raman spectra are very useful not just because the selection rules are different from the IR selection rules. The intensity of the peak depends on how much the geometry is changed in the electronically excited state. 

From high-resolution infrared spectra (193) the moments of inertia of and 62115 have been 

Guntherodt, R. Zeyher, Spin-Dependent Raman Scattering in Magnetic Semiconductors, Top. Appl. Phys. 54 [1984] 203/42. 

Safran, Raman Scattering Studies of Spin Order and Fluctuations in Europium Chalcogenides, J. Phys. Colloq. [Paris] 41 [1980] C5-223/C5-232. 

Guntherodt, Light Scattering in Magnetic Semiconductors, J. Magn. Magn. Mater. 11 [1979] 394/402. 

Dresselhaus, Optical Properties of the Europium Chalcogenide Magnetic Semiconductors, NATO Advan. Study Inst. B 60 [1980] 315/35. 

When a molecular gas is intensely irradiated with monochromatic light, usually from a laser, a spectrum of Raman lines is generated close to the strong elastic Rayleigh component. 

one may consider the implications of laser-Raman studies of the norbomyl ion. Raman spectra of the norbomyl cation at —70° to —80° were reported in the FSO3H—SbFs—SOj system (Olah et al., 1968). The spectra of it and related compounds are given in Table 10. 

The norbomyl cation and substituted nortricyclenes were shown to have five relatively weak bands in the C—H stretching region ( 3000 cm ). Only three were present in norbomane and its derivatives, and these were generally at lower frequency than those in the ion. 

In the C—C stretching region, the norbomyl ion and nortricyclene exhibit very strong peaks at 952 and 951 cm and similar spectra between 700 and 1000 cm . The alkylnorbomyl cations, 2-methyl and 2-ethyl, on the other hand, show substantial similarities to norbomane in this region. 

In our view, it is extremely difficult to use the Raman data to dismiss any structure of the norbomyl ion. The main reason for this is that a normal-coordinate analysis of the comer-protonated 

Main Raman Spectral Lines (cm ) of the Norbomyl and 2-Methyl- and 2-Ethylnorbornyl Cations and Vibrational Data 

Technical advances in spectrometers, detection systems and especially lasers as excitation sources have opened up the entire area of biochemistry for Raman studies in the last decade. General introductions to Raman spectroscopy are found in Tobin (1971), Anderson (1971) and Colthup et al, (1975). A review of biological applications has been published by Carey and Salares (1980). Reviews dealing specially with lipids are those by Wallach et al. (1979) and Verma and Wallach (1983). 

Sample handling and preparation is very easy, as in the case of IR spectroscopy. Commercial instruments belong to two main types, conventional scanning and optical multichannel analysers. The main difference between both types is that, in scanning spectrometers, the scattered light is collected and analysed, usually at 1 cm intervals (channels), whereas in optical multichannel analysers a 300-600 cm section of the Raman spectrum, projected on to the detector, is rapidly recorded in a computer memory without 

DPPC (suspension) Chain order Diff. spectr. 

PS + PS + DMPC + T c trans gauche ratio 1063-1130 1063-1130 abolishes Tc More trans at/below T. Hark and Ho (1980) 

DPPC +12 trans gauche ratio 1063-1130 I2 raises gauche fraction Loshchilova and Karvaly (1977) 

The vibrational spectra of N-methylthioacetamide and NN-dimethyl-thioacetamide have been discussed on the basis of normal-co-ordinate treatments. Other papers deal with i.r. and/or Raman spectroscopic 

Foks and J. Sawlewicz, Rorpr., Gdansk Tow. Nauk, Wydz., 1972, 121 (Chem. Abs., 1974, 

Sucharda-Sobczyk, D. Konopidska, and I. Z. Siemon, Bull. Acad, polon. Sci., Sir. Sci. chim., 1974, 22, 115. 

Schrader, W. Meier, K. Gottlieb, H. Agatha, H. Barentzen, and P. Bleckmann, Ber. Bunsengesellschaft phys. Chem., 1971, 75, 1263 P. Bleckmann, B. Schrader, and W. Meier, ibid., p. 1279. 

Ksandr, K. Volka, and P. Addmek, Coll. Czech. Chem. Comm., 1973, 38, 1137. 

When an incident beam of radiation of frequency y falls on a molecule, some radiation is scattered and in this scattered radiation we get, as well as v, frequencies y where vp is a fundamental frequency. This is called the Raman effect and when a fundamental frequency appears in the Raman spectrum it is said to be Raman active. 

An incident radiation field with an electric vector E induces a dipole moment M in a molecule. The components of M are  

Quantum mechanics tells us that the probability that Raman scattering involves the fundamental frequency vp depends on the integrals 

In a molecule with a centre of inversion, the irreducible representations in r are of u-type and those in P are of y-type and since cannot coincide with both a u and a (7-type irreducible representation, no fundamental frequency for this type of molecule can be both infrared and Raman active. 

In this section we will determine the differences in the infra-red and Raman spectra of methane CH4 and monodeuteromethane CH3D by 

The infrared (IR) spectra of 1,10-phenanthroline, its hydrate and perchlorate in the region 600-2000 cm have been obtained, and the principal features of the spectra interpreted. Further studies on the IR spectra of 1,10-phenanthroline, substituted 1,10-phenanthrolines, and 1,7-phenanthroline have also been reported. The IR spectrum of 4,7-phenanthroline in the region 650-900 cm has been analyzed, and the C—H out-of-plane deformation frequencies were compared with those of phenanthrene and benzo[/]quinoline. TTie IR spectra of salts of 1,10-phenanthroline have been taken, and the NH vibrations determined. - Infrared spectroscopy has been used to detect water associated with 1,10-phenanthroline and some of its derivatives on extraction into nitromethane from aqueous solution. The Raman spectrum of 1,10-phenanthroline has been compared with its IR spectrum. Recently, the Raman and IR spectra of all ten isomeric phenanthrolines were measured in solution and solid states, and the spectra were fully discussed.  

As for the change of dipole moment, the change of polarizability with vibrational displacement x can be expressed as a Taylor series 

By analogy with Equation (6.6) the vibrational Raman transition moment is given by 

Intensities of Raman transitions are proportional to R and therefore, from Equation (6.13), to (da/dx)g. Since a is a tensor property we cannot illustrate easily its variation with x instead we use the mean polarizability a, where 

According to a factor group analysis of R (space group I4cm with Z = 4), vibration modes can be presented in the center of the Brillouin zone (wave 

The Ai, Bi, B2 and E modes are active in the Raman spectrum, Ai is polarized along c and E mode is polarized perpendicular to c. A and E modes are active in the IR spectrum as well. 

Raman spectra obtained at different orientations of the crystal are presented in Fig. 104. Axes denoted as a, b and c correspond to directions [no], 

The strongest mode observed near 800 cm 1 is polarized along c and is a totally symmetrical vibration mode (Ai) corresponding to the niobium-oxygen vibrations Vs (NbO) of infinite chains (NbOFf), running along the c -axis. The mode observed at 615 cm 1 is polarized perpendicular to c and corresponds to the NbF vibrations of the octahedrons of the same chains. The mode at 626 cm 1 is attributed to NbF vibrations of isolated complex ions - NbF72. The lines at 377, 390 and 272 cm 1 correspond to deformation modes 8(FNbF) of the two polyhedrons. 

The most striking peculiarity concerns the TO-LO splitting (788-847 cm 1) that was observed for the NbO stretching mode (Ai symmetry) polarized along the c axis. Fig. 105 shows the transformation of the spectrum as dependent on 

All chemical shifts are measured from external Me4Si. 

Evidence for planarity or near planarity of the sp2 center of trivalent alkyl cations thus comes from the combined results of NMR ( H and 13C) IR, and Raman spectroscopy31-32, 34.  

As originally pointed out by Vaska [26], dioxygen stretching frequencies of complexes known at that time could be divided into two 

As more dioxygen complexes were prepared and Raman spectroscopy became increasingly available, many new data were reported. Often the 0-0 vibration is infrared-inactive and can only be observed in Raman and Resonance Raman spectra. 

Nakamoto and coworkers [203-208] made very detailed studies of a number of superoxo complexes especially among possible models for hemoglobin, such as MnCTPPlO, FeCTPPlO and Co(TPP)02 (TPP is 

The effects of basic ligands bonded axially to square planar cobalt complexes such as Co(salen), [N,N -ethylenebis(sallcylideneiminato)-cobalt(II)] [209,210] or Co(TPP) [211,212] on the 0 stretching 

Infrared spectra of O -adducts are useful sources of information 

Sheline, R. K., The Effective Methyl Mass and Its Use in Determining the Force Constants and Character of Metallo-Organic Bonds, J. Chem. Phys. 18 [1950] 602/6. 

Noltes, J. G., Henry, M. C., Janssen, M. J., An Infrared Absorption Band Characteristic for Aromatic Compounds of Fourth Main Group Elements, Chem. Ind. [London] 1959 298/9. 

Okawara, R., Sakiyama, M., Infrared Spectra of Organic Silicon, Germanium, Tin, and Lead Compounds, Kagaku Ryolkl Zokan No. 45 [1961] 127/64. 

Ramachandran, J., Balasubramanlan, A., The Infrared and the Near-Ultraviolet Absorption Spectra of Polyphenyl Derivatives of the Elements of Groups IVb and Vb, Can. J. Chem. 39 [1961] 171/9. 

Vyshinskii, N. N., Rudnevskll, N. K., Vibrational Spectra of Certain Organometallic Compounds of the Group IV Elements, Opt. Spektroskopiya 10 [1961] 797/9 Opt. Spectrosc. [USSR] 10 [1961] 421/2. 

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Fig. IV-14. Resonance Raman Spectra for cetyl orange using 457.9-nm excitation. [From T. Takenaka and H. Fukuzaki, Resonance Raman Spectra of Insoluble Monolayers Spread on a Water Surface, J. Raman Spectr., 8, 151 (1979) (Ref. 157). Copyright Heyden and Son, Ltd., 1979 reprinted by permission of John Wiley and Sons, Ltd.]...

The behavior of insoluble monolayers at the hydrocarbon-water interface has been studied to some extent. In general, a values for straight-chain acids and alcohols are greater at a given film pressure than if spread at the water-air interface. This is perhaps to be expected since the nonpolar phase should tend to reduce the cohesion between the hydrocarbon tails. See Ref. 91 for early reviews. Takenaka [92] has reported polarized resonance Raman spectra for an azo dye monolayer at the CCl4-water interface some conclusions as to orientation were possible. A mean-held theory based on Lennard-Jones potentials has been used to model an amphiphile at an oil-water interface one conclusion was that the depth of the interfacial region can be relatively large [93]. 

Fig. XVI-5. Resonance Raman spectra of MDMA adsorbed on ZnO (a) in the presence of 100 torr of NH3 (b) after evacuation of the NH3 from the cell. [Reprinted with permission from J. F. Brazdil and E. B, Yeager, J. Phys. Chem., 85, 1005 (1981) (Ref. 79). Copyright 1981, American Chemical Society.]...

Herzberg G 1945 Molecular Spectra and Molecular Structure II Infrared and Raman Spectra of Polyatomic Molecules (New York Van Nostrand-Reinhold)... 

The pioneering use of wavepackets for describing absorption, photodissociation and resonance Raman spectra is due to Heller [12, 13,14,15 and 16]- The application to pulsed excitation, coherent control and nonlinear spectroscopy was initiated by Taimor and Rice ([17] and references therein). 

A beautiful, easy-to-read introduction to wavepackets and their use in interpreting molecular absorption and resonance Raman spectra. 

Infonuation about the haeme macrocycle modes is obtained by comparing the resonance Raman spectra of deoxyHb with HbCO. The d-d transitions of the metal are too weak to produce large enliancement, so the... 

Sakamoto A, Okamoto H and Tasumi M 1998 Observation of picosecond transient Raman spectra by asynchronous Fourier transform Raman spectroscopy 1998 Appl. Spectrosc. 52 76-81... 

Jones WT and Stoicheff B P 1964 Inverse Raman spectra induced absorption at optical frequencies Phys. Rev. Lett. 13 657-9... 

Fleischmann M, Hendra P J and McQuillan A J 1974 Raman spectra of pryridine adsorbed at a silver electrode Chem. Phys. Lett. 26 163-6... 

Albrecht M G and Greighton J A 1977 Anomalously intense Raman spectra of pyridine at a silver electrode J. Am. Chem. Soc. 99 5215-17... 

De Santis A, Sampoli M, Mazzacurati V and Ricci M A 1987 Raman spectra of water in the translational region Chem. Phys. Lett. 133 381-4... 

Figure Bl.22.6. Raman spectra in the C-H stretching region from 2-butanol (left frame) and 2-butanethiol (right), each either as bulk liquid (top traces) or adsorbed on a rough silver electrode surface (bottom). An analysis of the relative intensities of the different vibrational modes led to tire proposed adsorption structures depicted in the corresponding panels [53], This example illustrates the usefiilness of Raman spectroscopy for the detennination of adsorption geometries, but also points to its main limitation, namely the need to use rough silver surfaces to achieve adequate signal-to-noise levels.

Nakamoto K 1978 Infrared and Raman Spectra of Inorganic and Coordination Compounds 3rd edn (New York Wiley-Interscience)... 

Figure C 1.5.7. Surface-eiilianced Raman spectra of a single rhodamine 6G particle on silver recorded at 1 s intervals. Over 300 spectra were recorded from this particle before tlie signals disappeared. The nine spectra displayed here were chosen to highlight several as yet unexplained sudden changes in botli frequency and intensity. Reprinted witli pennission from Nie and Emory [ ]. Copyright 1997 American Association for tlie Advancement of Science.

Experimentally, local vibrational modes associated witli a defect or impurity may appear in infra-red absorjrtion or Raman spectra. The defect centre may also give rise to new photoluminescence bands and otlier experimentally observable signature. Some defect-related energy levels may be visible by deep-level transient spectroscopy (DLTS) [23]. 

Rossetti R, Nakahara S and Brus L E 1983 Quantum size effects In the redox potentials, resonance Raman spectra and electronic spectra of CdS crystallites In aqueous solution J. Chem. Phys. 79 1086... 

In an ambitious study, the AIMS method was used to calculate the absorption and resonance Raman spectra of ethylene [221]. In this, sets starting with 10 functions were calculated. To cope with the huge resources required for these calculations the code was parallelized. The spectra, obtained from the autocorrelation function, compare well with the experimental ones. It was also found that the non-adiabatic processes described above do not influence the spectra, as their profiles are formed in the time before the packet reaches the intersection, that is, the observed dynamic is dominated by the torsional motion. Calculations using the Condon approximation were also compared to calculations implicitly including the transition dipole, and little difference was seen. 

Woodruff and co-workers introduced the expert system PAIRS [67], a program that is able to analyze IR spectra in the same manner as a spectroscopist would. Chalmers and co-workers [68] used an approach for automated interpretation of Fourier Transform Raman spectra of complex polymers. Andreev and Argirov developed the expert system EXPIRS [69] for the interpretation of IR spectra. EXPIRS provides a hierarchical organization of the characteristic groups that are recognized by peak detection in discrete ames. Penchev et al. [70] recently introduced a computer system that performs searches in spectral libraries and systematic analysis of mixture spectra. It is able to classify IR spectra with the aid of linear discriminant analysis, artificial neural networks, and the method of fe-nearest neighbors. 

As mentioned, we also carried out IR studies (a fast vibrational spectroscopy) early in our work on carbocations. In our studies of the norbornyl cation we obtained Raman spectra as well, although at the time it was not possible to theoretically calculate the spectra. Comparison with model compounds (the 2-norbornyl system and nortri-cyclane, respectively) indicated the symmetrical, bridged nature of the ion. In recent years, Sunko and Schleyer were able, using the since-developed Fourier transform-infrared (FT-IR) method, to obtain the spectrum of the norbornyl cation and to compare it with the theoretically calculated one. Again, it was rewarding that their data were in excellent accord with our earlier work. 

The two absorption bands, at 1050 and 1400 cm , which appear in the Raman spectra of solutions of nitric acid in concentrated sulphuric acid are not attributable to either of the acid molecules. In oleum the lower band appears at 1075-1095 cm. That these bands seemed to correspond to those in the spectra of anhydrous nitric acid and solid dinitrogen pentoxide caused some confusion in the assignment of the spectrum. The situation was resolved by examining the Raman spectra of solutions of nitric acid in perchloric or selenic acids , in which the strong absorption at 1400 cm is not accompanied by absorption at about 1050 cm . Thus, the band at 1400 cm arises from the nitronium ion, and the band at about 1050 cm can be attributed in the cases of nitric acid and solid dinitrogen pentoxide to the nitrate ion formed according to the following schemes ... 

THE STATE OF NITRIC ACID IN INERT ORGANIC SOLVENTS The absence of ions in mixtures of acetic acid and nitric acid is shown by their poor electrical conductivity and the Raman spectra of solutions in acetic acid, nitromethane, and chloroform show only the absorptions of the solvent and molecular nitric acid the bands corresponding to the nitronium and nitrate ions cannot be detected. -... 

A study of the Raman spectra of similar mixtures confirmed and extended these conclusions. The existence of the following two equilibria was postulated ... 

Raman spectra of 2-aminothiazoles have been described (124). 

Infrared and Raman spectra of A-4-thiazoline-2-thione and of isotopi-cally labeled derivatives (56. 59) were interpretated completely. (Table VII-41. 

Until 1962 the infrared and Raman spectra of thiazole in the liquid state were described by some authors (173, pp. 194-200) with only fragmentary assignments. At that date Chouteau et al. (201) published the first tentative interpretation of the whole infrared spectrum between 4000 and 650 cm for thiazole and some alkyl and haloderivatlves. They proposed a complete assignment of the normal modes of vibration of the molecule. 

The infrared and Raman spectra of many alkyl and arylthiazoles have been recorded. Band assignment and more fundamental work has been undertaken on a small number of derivatives. Several papers have been dedicated to the interpretation of infrared spectra (128-134, 860), but they are not always in agreement with each other. However, the work of Chouteau (99, 135) is noteworthy. The infrared spectrum of thiazole consists of 18 normal vibrations as well as harmonic and combination bands. 

Each of these can be assigned to one of the symmetry species of the point group to which the molecule belongs. These assignments are indicated in the right-hand column of each character table given in Appendix A and will be required when we consider vibrational Raman spectra in Section 6.2.3.2. 

Rotational Raman spectra of diatomic and linear polyatomic molecules... 

Herzberg, G. (1990) Infrared and Raman Spectra, Krieger, Florida. 

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