Gases Raman spectra

It is an intensely reactive and hygoscopic yellow-brown substance (m.p. 75-78°C) its volatility suggests a low molecular mass Mossbauer spectra indicate 6-coordinate gold while the Raman spectrum is interpreted in terms of cw-bridged octahedral units. In the gas phase at 170°C, it comprises dimers and trimers [29] (electron diffraction). 

The quantum theory of spectral collapse presented in Chapter 4 aims at even lower gas densities where the Stark or Zeeman multiplets of atomic spectra as well as the rotational structure of all the branches of absorption or Raman spectra are well resolved. The evolution of basic ideas of line broadening and interference (spectral exchange) is reviewed. Adiabatic and non-adiabatic spectral broadening are described in the frame of binary non-Markovian theory and compared with the impact approximation. The conditions for spectral collapse and subsequent narrowing of the spectra are analysed for the simplest examples, which model typical situations in atomic and molecular spectroscopy. Special attention is paid to collapse of the isotropic Raman spectrum. Quantum theory, based on first principles, attempts to predict the. /-dependence of the widths of the rotational component as well as the envelope of the unresolved and then collapsed spectrum (Fig. 0.4). 

In the conclusion of the present chapter we show how comparison of NMR and Raman scattering data allows one to test formulae (3.23) and (3.24) and extract information about the relative effectiveness of dephasing and rotational relaxation. In particular, spectral broadening in nitrogen caused by dephasing is so small that it may be ignored in a relatively rarefied gas when spectrum collapse proceeds. This is just what we are going to do in the next sections devoted to the impact theory of the isotropic Raman spectrum transformation. 

Fig. 3.6. Density transformation of nitrogen isotropic Raman spectrum normalized to a maximum [89] (gas density is given in amagat).

IR and Raman spectroscopy have been commonly used and, for example, the effects of pressure on the Raman spectrum of a zinc compound with a N2C12 coordination sphere around the metal, have been investigated.28 IR spectroscopy has been utilized in studies of the hydration of zinc in aqueous solution and in the hydrated perchlorate salt.29 Gas phase chemistry of zinc complexes has been studied with some gas phase electron diffraction structures including amide and dithiocarbamate compounds.30-32... 

Explosive decomposition occurred dining purification by GLC and when running the gas phase laser Raman spectrum. 

The vibration-rotation gas-phase Raman spectrum of C3 O2 was obtained for the first time by Smith and Barrett using a 2-watt argon-ion laser. The results of this experiment gave new information about the bonding potential function for the central carbon bonding fundamental. 

Binary Systems and Related Compounds.—Halides. The thermodynamics of gas-phase equilibria in the W-F2 and W-F2-H2 systems at high temperatures have been described.The Raman spectrum of solid MoF exhibits Mo—F stretching bands at 746, 722, and 690 cm These results suggest that the compound has a similar structure to NbF4, with each molybdenum co-ordinated to six fluorine atoms.The Raman spectrum of crystalline M0F5 has also been reported and interpreted in terms of the crystal structure.The electronic spectrum of liquid M0F5 has been determined and shown to be consistent with a trigonal-bipyramidal molecular unit. ... 

The pyramidal structure of symmetry Cg for FCIO2 was also confirmed by vibrational spectroscopy. E. A. Smith et al. (271) and Arvia and Aymonino (6) reported the infrared spectrum of the gas. D. F. Smith et al. (270) studied the infrared spectrum of the gas, measured the 3501-3701 i6Q i8o isotopic shifts, recorded the Raman spectrum of the liquid, and carried out a normal coordinate analysis. The observed frequencies and their assignment are summarized in Table XIII. 

Andrews and co-workers have recently reported (5) C1- C1 and i 0- 0 isotopic shifts for the infrared spectrum of argon matrix-isolated FCIO2. Tantot (282) has studied in his thesis work the infrared and Raman spectra of the gas, the Raman spectrum of the neat liquid and of HF solutions, and the infrared and Raman spectra of the solid. 

The fundamental vibrations (8 stretching, 10 deformation and 3 torsional modes) of tri-fluoromethyl peroxynitrate (1) can be assigned from the FUR spectrum in the gas phase and FT-Raman spectrum of the liquid. The high-frequency stretching modes are characteristic and easily assigned, except for the Vs(CF3) and Vs(N02) fundamental modes, which overlap in the gas-phase IR spectrum. Near agreement is obtained between the experimental and the theoretically calculated vibrational spectra°°. Due to the Cj symmetry of the molecule, all the fundamental modes (7 stretching, 8 deformation and 3... 

Figure 12.22 Our Raman spectrum of liquid [C4Cilm][Tf2N. Apparently the splitting between the two conformation sensitive bands for the [Tf2N - ion, near —400 cm", is not so large in this liquid as for the 1-ethyl [C2Cjlm][Tf2N] case [109]. The CFg symmetric stretching and deformation bands are seen at 1242 and 742 cm". The AA/GA conformational equilibrium bands at 500-700 cm" discussed in relation with Figure 12.6 can also be weakly seen.

See lext. XD = X-ray diffraction 1R = infrared spectrum R = Raman spectrum UV = ultraviolet spectrum H-NMR = ]HNMR spectrum C-NMR = 13CNMR spectrum F-NMR =, 9FNMR spectrum MS = mass spectrum PES — photoelectron spectrum E - electric polarization and dielectric loss measurements D = dipole moment measurements TDPAC = time differential perturbed angular correlation measurements GC = gas chromatography TA = thermal analysis M = molecular weight A = electrical conductance. c Isolated as the THF adduct M(dik)Cl3-C4HgO. 

Most fundamental work on the vibrational spectra of azoles appeared in the period 1960-1980. Examples of more recent work include (i) a complete assignment of the gas-phase IR spectrum of indazole (93JCS(F1)4005) (ii) IR spectral data were used to determine the enthalpies of 0—H. . . N and N—H. . . O bonds in complexes of formic acid and 3,5-dimethylpyrazole (87MI301-01) (iii) the vibrational assignment of the Raman spectrum of polycrystalline pyrazole (92MI301-01) based on 3-21G calculations. 

Fig. 4.15 Raman spectrum of a diatomic gas. The central line corresponds to photons scattered with no frequency change (Rayleigh scattering).

Figure 5.13 shows a typical experimental arrangement for obtaining the Raman spectrum of a gaseous sample. Radiation from the laser source is focused by the lens L, into a cell containing the sample gas. The mirror Mj reflects this radiation back into the cell to increase... 

In Ref. (163) the techniques introduced above were illustrated for He-He and He-H2 collisional complexes. In Refs. (316,317) the property functions were applied in full quantum-statistical calculations of the dielectric second virial coefficient and of the polarized and depolarized Raman spectrum of the He gas. Some further applications were reported by Rizzo and collaborators318- 322. 

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