Frequency downshift

It is obvious from Figure 3.9 that both the frequency and bandwidth of the C=0 stretching mode displays remarkable sensitivity to the polarity and the H-bonding ability of the solvent. The frequency downshift and slight bandwidth broadening observed when changing the solvent from cyclohexane to MeCN is due to the nonspecific electrostatic solvent-solute interaction affected mainly by the solvent... 

Resonance Raman (RR) experiments have also provided valuable data on the structure of the electron. RR spectra of aqueous solvated electrons revealed enhancements of the water inter- and intra-molecular vibrations demonstrating that electronic excitation was significantly coupled to these modes. Frequency downshifts of the resonantly enhanced H2O bend and stretch were explained by charge donation into solvent frontier orbitals. RR spectra in primary alcohols (methanol, ethanol, propan-l-ol) revealed strong vibronic coupling of the solvated electron to at least five normal modes of the solvent. The spectra showed enhancements of the downshifted OH stretch. 

Finally, in second order, the Raman feature at — 3180 cm" observed in Co- and Ni/Co-catalyzed single-wall nanotube corresponds to a significantly downshifted 2 x fjg mode, where E g represents the mid-zone (see Figs, la and lb) frequency maximum of the uppermost optic branch seen in graphite at 3250 cm". ... 

Raman spectra have also been reported on ropes of SWCNTs doped with the alkali metals K and Rb and with the halogen Br2 [30]. It is found that the doping of CNTs with alkali metals and halogens yield Raman spectra that show spectral shifts of the modes near 1580 cm" associated with charge transfer. Upshifts in the mode frequencies are observed and are associated with the donation of electrons from the CNTs to the halogens in the case of acceptors, and downshifts are observed for electron charge transfer to the CNT from the alkali metal donors. These frequency shifts of the CNT Raman-active modes can in principle be u.sed to characterise the CNT-based intercalation compound for the amount of intercalate uptake that has occurred on the CNT wall. 

Vibrational Frequencies (cm" ), Isotope Downshifts (cm" in Parentheses), and Assignments for the Fe-S Stretching Modes of Oxidized FeaSJSa Centers in Beef Heart Aconitase, a. vinelandii Fdl, T. thermophilus Fd, P. furiosus Fd, D. gigas Fdll, and... 

The porphyrin skeletal mode frequencies are all slightly lower both for the triplet and for the ground state. Table II lists the triplet downshifts, l-7cm , along with the shifts observed for radical cations (13a) and anions (13b) for MgTPP and ZnTPP reported by Itoh and coworkers. Since the triplet excited states are formed by... 

Experimentally, band assignments are facilitated by the observation of isotope shifts. As shown in Table 1-3, the vibrational frequency of H2 (4,160 cm 1) is markedly downshifted (2,994 cm 1 when H is replaced by D. The magnitude of this isotope shift is predicted by Eq. (1-40) ... 

H21602/H21802 substitution. The observed downshift of the v(Fe=0) in going from alkaline to neutral solution has been attributed to the formation of a hydrogen bond in neutral solution as depicted in Fig. 6-8 (13). These v(Fe=0) frequencies are much lower than those of 0=Fe(TPP-<4) (853 cm-1 (Section 3.2.3) because HRP-II is six-coordinate. Kitagawa s review (15) provides more information on RR spectra of reaction intermediates of heme proteins. 

Infrared frequencies are in regular type and Raman frequencies are in italic. hThe lsO downshifts are given in parentheses. 

In summary, the irreversible intensity decrease and downshift of the on-top CO frequency at 300 K for pressures > 100 mbar and the appearance of low-frequency features at elevated temperatures and pressures (> 600 K > 1 mbar) most likely... 

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