Anomalous polarization

The considerable electrical anisotropy of this salt is made still more evident on the room-temperature polarized infrared reflection spectra [30] (see also Chapter 6 and Fig. 1 of this chapter). In addition, these reflection spectra give a remarkably clear information on the existence of strong coupling between the quasi-one-dimensional electronic system and the symmetric ag vibrational modes of the TCNQ molecules. More precisely, under the effect of this coupling, these particular modes, which are normally Raman active but infrared nonactive, acquire an anomalous intense infrared activity together with an anomalous polarization [20,30,31]. 

Figure 10 Parallel ( ) and perpendicular ( ) scattered resonance Raman spectra from NiP in CS2 showing the anomalously polarized bands (labeled) associated with the ring A2g vibrations...

Resonance (special cases) Anomalously polarized (nontotally symmetric modes, normally Raman forbidden) Nonsymmetric, ap a p p >3/4... 

A-term (totally symmetric modes), B-term (nontotally symmetric modes), and C-term (first overtones and binary combinations of vibronically active modes) effective Anomalously polarized (ap) and inversely polarized (ip) bands attainable as well Overtones and combination bands common... 

Chaney SB, Zhang ZY, Zhao YP (2006) Anomalous polarized absorbance spectra of aligned Ag nanorod arrays. Appl Phys Lett 89(5) 053117... 

Iridium(iv).—Reduction of IrCli to IrClg by various transition-metal ions does not change the inner co-ordination sphere. A resonance Raman effect has been observed for IrClg". Anomalous polarization was found on all Raman bands and this was ascribed to Jahn-Teller distortions in the excited electronic state. I.r. and... 

Figure 1.35 shows the RR spectra of Ni(OEP) with excitation near the B, gi and Qq transitions as obtained by Spiro and coworkers [109]. As discussed in Sec. 1.20, polarization properties are expected to be Aig (p, polarized). Big and B2g dp, depolarized), and A2 ap, anomalous polarization). These polarization properties, together with normal coordinate analysis, were used to make complete vibrational assignments of Ni(OEP) [110]. It is seen that the spectra obtained by excitation near the go band (bottom traces) are dominated by the dp bands Big and B2g species), while those obtained by excitation between the go and gi bands (middle traces) are dominated by the ap bands (A2 species). The spectra obtained by excitation near the B band (top traces) are dominated by the p bands Aig species). In this... 

As will be shown in Sec. 2.8, anomalously polarized bands have also been observed in the RR spectra of the IrCl ion, although their origin is different from the vibronic coupling mentioned above [111,112]. 

IR, infrared R, Raman RR, resonance Raman p, polarized dp, depolarized ap, anomalous polarization ia, inactive. 

Hexachloroiridates(IV) may be prepared by (i) chlorinating a mixture of iridium powder and an alkali metal chloride (ii) in solution, by the addition of an alkali metal chloride to a suspension of hydrous Ir02 in aqueous HC1 or (iii) by the oxidation of [IrCl ] " by O2 in acidic media. Oxidation by Oj probably occurs via reaction (122), with = + 0.21 V. Fine" has suggested that the reverse of reaction (122) occurs in alkaline media. The black crystalline sodium salt Na2[IrCls] is water soluble, and is the usual starting material for the synthesis of other iridium(IV) coordination complexes. The resonance Raman spectrum of (NBu4)2[IrCle] reveals anomalous polarization of all bands this has been ascribed to Jahn-Teller distortions present in the excited electronic state. The single-crystal electronic spectra of various [IrCl ] " salts have also been reported." ... 

Fig. 17 A-C. Excitation profiles of the resonance Raman bands of Ni(OEC) in CH2CI2 and its absorption spectrum in which the arrows indicate the excitation wavelengths used for Raman measurements A) polarized bands, B) depolarized bands, C) anomalously polarized bands...

Argyle et al. (1975) have determined the total magnetization and Co sublattice magnetization dependence on temperature from Kerr rotation measurements, for alloys prepared by rf sputtering. They observed anomalous polarization Kerr loops due to interface effects relative to the Gd oxidation at the surface. They concluded that the formation of a Gd203 layer results in an enrichment of Co in the top (film-air interface) with a thickness of 50-100 A. In order to have a... 

Benzyloxypentanol treated with 1 eq. NaH in 1 1 THF/DMF, 0.1 eq. Bu4N T added followed by 0.6 eqs. iodomethyltrimethylsilane, and allowed to react at 0-5° for 30 min product. Y 89% (1 1.1 mixture of methyl and silyl ethers). Reaction appears to involve anomalous polarization of the carbon-silicon bond with methyl as leaving group. F.e.s. T.K. Chakraborty, G.V. Reddy, J. Chem. Soc. Chem. Commun. 1989, 251-3. 

Uber eine Anomalie bei der Polarisation der Ramanstrahlung (On the anomalous polarization of Raman lines), Naturwissenschaften 19, 375 (1931). 

Unless y 2 = q (nonresonant Raman), measurement with circularly polarized light is needed to determine the three invariants. The results are usually expressed as the depolarization ratio / (O/, vi)/4"(0/] Vi). For nonresonant Raman scattering this equals 3/4 for a = is lower otherwise, and reaches zero if a = a ( ) (totally symmetric vibration). In resonant Raman, can be different from zero, and the depolarization ratio can exceed 3/4 ( anomalous polarization ). 

Under resonance or near-resonance conditions in certain rare instances, g 0. This arises because, for certain modes, a can become antisymmetric with a pa = —a pa, giving rise to anomalously polarized bands with p > 3/4. In the limiting case when g = = 0, but g 0,... 

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