Ungerade vibrations

In oxidized Rieske proteins, a larger number of peaks are observed that have been attributed to vibrations of the iron-sulfur core this is indicative of the reduced symmetry of the iron-sulfur core in Rieske proteins since ungerade vibrations are Raman-inactive in the centro-symmetric (in first approximation) [2Fe-2S]-Cys4 core (point group D2h or Cih) while the corresponding modes are Raman-active in C2 symmetry. The characteristic peak of the SL mode of proteins con-... 

Table 9.8. Second-Order Spin-Orbit Selection Rules for the Appearance of Ungerade Vibrations in Singlet-Triplet Spectra...

The review describes the application of the CLF intensity model to 43 chromophores. The ability to reproduce the observed intensity distributions, including those from experiments using linearly and circularly polarized light, is impressive. For example, the band areas for both the unpolarized absorption and CD spectra of Co(a-isospartein)Cl2 are virtually perfect while in centrosymmetric complexes such as [PtCU] ", [PtBr4] , and [PdCU] " the vibronic analysis can also establish the relative importance of the possible eontributing ungerade vibrational modes to the overall intensity. In these cases, the e mode aeeounts for more than half of the total. 

When the Ln ion is situated at a centrosymmetric site (i.e., with an inversion center), the pure electronic transitions between 4 levels are ED forbidden [10]. Magnetic dipole transitions (which are up to 10 times weaker than ED transitions) may then be allowed between states of the same parity in the solid if (8) is satisfied, since the magnetic dipole operator, Fq, is of even parity. The only way to destroy the centrosymmetry of Ln " and permit an ED transition between two electronic states is by motions of odd (ungerade) vibrations so that the electronic spectra of Ln " at an inversion center of a crystal are vibronic (vibrational-electronic) in nature. The transition selection rules then become ... 

E s are the unperturbed energies of the electronic and vibrational states, respectively, and Bm is a constant energy factor which depends on the M excited state. It appears from Eq. (6.5) that ungerade symmetry of inverse energy mismatch between the relevant levels. 

The dipole moment operator ( x) has associated with it ungerade character so the integral will be zero if v i[ and v g are both either gerade or ungerade. Again, Laporte-forbidden transitions do occur (with 10 -10 the intensity of fully allowed transitions) because of mixing of the orbitals in the excited state in noncentrosymmetric sites, and even in centrosym-metric sites as a result of vibrations of the metal atoms away from the center of symmetry (vibronic coupling). 

The potential energy surfaces (LEPS A from Refs. (8.10)). the effective potentials U (n=0 gerade and ungerade symmetry) and the bound states of the collinear IHI and lOI are shown in Fig. 4. As argued for the Cl+HCl system the reaction is very adiabatic, and thus the effective potentials and the adiabatic eigen-energies e (r) coincide within 10 eV. It should be noticed that isotopic suBstitution of the hydrogen atom by its heavier isotope deuterium tends to destabilize the vibrational bonded molecule. 

The nonradiative decay pathways for the (X2E+ )np Rydberg states of H2 have been examined by McCormack, et al, (1993). Selected vibrational-rotational levels of the E, FXE+ state were excited by two-photon transitions from the X E+ state and the ungerade Rydberg states were examined by a double resonance excitation scheme via the selected levels of the E, F state. 

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