Halogens, resonance Raman

Resonance Raman effects in halogen gases have been observed by Holzer etal. 207a). with an appropriate choice of exciting lines from an argon laser either resonance Raman effect or resonance fluorescence could be observed. The difference between the two spectra is discussed. In the case of a strong resonance Raman effect, overtone sequences up to the 14 harmonic could be observed. 

Raman spectra of chlorine, bromine, and iodine gas were first recorded by Flolzer et al. (1970) with argon laser excitation, the latter two halogens showed a strong resonance Raman effect. The numerous results of later investigations are presented in Sec. 6.1. on the resonance Raman effect. 

Both expressions for af, (Eqs. 6.1-18 and 6.1-19) have been used to numerically calculate the resonance Raman intensities of halogen and interhalogen molecules and their dependence on the incident laser energy =Hwq (Rousseau and Williams, 1976 Baierl and Kiefer, 1980, 1981 Ganz et al., 1990, 1992 Ganz and Kiefer, 1993a, 1994). 

Also linear chain complexes such as Pt(etn)4Cl3 which is known colloquially as Wolf-fram s red (etn being an abbreviation for ethylamine) have been studied successfully by resonance Raman spectroscopy (Clark, 1984). As example, we show in Fig. 6.1-12 the resonance Raman spectrum of a related halogen-bridged linear-chain species, [Pt(pn)2] [Pt(pn)2Br2] [Cu3Br5]2 (Clark et al., 1980). Although this species contains a complicated copper bromine chain, the resonance Raman spectrum (Fig. 6.1-12) is completely dominated by bands attributed to the v fundamental and its overtones n U[ of the platinum-bromine chain. 

Raman spectrum of I2 is observed. A solution of the Br2 cation also gives a resonance Raman spectrum with a fundamental of 360 cm and strong overtones 14). Edwards and Jones (17) reported that solid Br2" Sb3Pie has a Raman band at 368 cm which they attributed to the Brg cation. Table I shows the stretching frequencies, absorption maxima, and bond lengths of the halogens and the diatomic halogen... 

Table 2.2c lists the vibrational frequencies of triatomic halogeno compounds. The resonance Raman spectrum of the I3 ion gives a series of overtones of the Vi vibration [408,409]. The resonance Raman spectra of the l2Br and IBr2 ions and their complexes with amylose have been studied [410]. The same table also lists the vibrational frequencies of XHY-type (X,Y halogens) compounds. All these species are linear except the ClHCl ion, which was found to be bent by an inelastic neutron scattering (INS) and Raman spectral study [402]. 

W Holzer, WF Murphy, HJ Bernstein. Resonance Raman effect and resonance fluorescence in halogen gases. J Chem Phys 52 399-407, 1970. 

Janda KC, Kerenskaya G, Goldschleger lU, Apkarian VA, Fleischer E (2008) UV-visible and resonance raman spectroscopy of halogen molecules in clathrate-hydrates. In Proceedings of... 

Experimentally, the structures are determined by the use of various physical methods such as vibrational spectroscopy, both in the Raman and IR, NMR, or diffraction methods. Other accepted physical measurements, such as conductivity, cryoscopy, magnetic properties, electronic spectra in the UV and visible ranges, nuclear quadmpole resonance (NQR), and Mossbauer spectroscopy have also been applied. Table 3 summarizes various geometric structures found in halogen compounds, coordination numbers, bonding and nonbonding electronic arrangements, and symmetries. 

Fourier transform infrared spectroscopy was applied to the study of lac resin, a complex natural resin of insect origin, and some of its derivatives. The results obtained by this method are compared with those from earlier studies that used classical methods of chemical analysis. Experiments include the preparation of hard and soft resins, dewaxed lac, ammoniated lac, lac acetal, halogenated lac, hydrolysed lac, rebuilt lac (rebulac), and the preparation of lac metal salts. It is found that FTIR has several advantages over classical methods, but that FTIR data requires supplementing by other instrumental techniques such as FT-Raman spectroscopy and solid state nuclear magnetic resonance. 21 refs. 

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