Jahn-Teller effect analysis

Cossart-Magos C, Cossart D, Leach S, Maier JP, Misev L (1983) High-resolution gas phase emission and laser induced fluorescence excitation spectra of 1,3,5-C6fsh and l,3,5-c f3d critical bands in the Jahn-Teller effect analysis. J Chem Phys 78 3673... 

Fig. 5. The pseudo-Jahn-Teller effect in ammonia (NH3). (a) CCSD(T) ground state potential energy curve breakdown of energy into expectation value of electronic Hamiltonian (He), and nuclear-nuclear repulsion VNN. (b) CASSCF frequency analysis of pseudo-Jahn-Teller effect showing the effect of including CSFs of B2 symmetry is to couple the ground and 1(ncr ) states to give a negative curvature to the adiabatic ground state potential energy surface for the inversion mode.

TL OEt) ]224 with distortions due to M—M bonding. Crystal structure analysis of [W4(OEt)i6] (Figure 22) reveals the presence of two short W—W bonds (2.645 and 2.76 A) and two long bonds of 2.93 A. In this structure, there is a total of five possible W—W interactions, and thus, to form five bonds of order one, ten electrons are required. Only eight metal electrons are available for metal-metal bonding, which leads to the observed distortions. It has been suggested that this distortion results from a novel second order Jahn-Teller effect.225... 

The strategy of vibronic analysis is to regard the molecular skeleton in the higher possible symmetry, analyzing the forces distorting or keeping this structure. In case of distortion, a Jahn-Teller (JT) or pseudo Jahn-Teller effect (PJT) takes place. Even in the absence of distortion, a vibronic part exists inside of force constants of each normal vibration mode and its analysis could offer particular insight into molecular structure. 

In the master formula for the analysis of the pseudo-Jahn-Teller effect, the total curvature of the adiabatic potential surface, K, is partitioned in a so-called non vibronic part K0 and the vibronic one Kv, namely K = K0 + Kv, with... 

Cu isotopes both with nuclear spin I-3/2. The nucle r g-factors of these two isotopes are sufficiently close that no resolution of the two isotopes is typically seen in zeolite matrices. No Jahn-Teller effects have been observed for Cu2+ in zeolites. The spin-lattice relaxation time of cupric ion is sufficiently long that it can be easily observed by GSR at room temperature and below. Thus cupric ion exchanged zeolites have been extensively studied (5,17-26) by ESR, but ESR alone has not typically given unambiguous information about the water coordination of cupric ion or the specific location of cupric ion in the zeolite lattice. This situation can be substantially improved by using electron spin echo modulation spectrometry. The modulation analysis is carried out as described in the previous sections. The number of coordinated deuterated water molecules is determined from deuterium modulation in three pulse electron spin echo spectra. The location in the zeolite lattice is determined partly from aluminum modulation and more quantitatively from cesium modulation. The symmetry of the various copper species is determined from the water coordination number and the characteristics of the ESR spectra. 

In [Mn(urea)6]3+ all six Mn—O distances are equal (1.986 A) but analysis of displacements of the O atoms and electronic spectra are in agreement with a dynamic Jahn-Teller effect. 

Detailed analyses of the density distributions and chemical bindings were also given by Kern and Karplus (1964) for HF and by Ransil and Sinai (1967) for Li2, N2, F2, HF, and LiF. Politzer et al. gave a force analysis for CO (Politzer, 1965) and NO (Politzer and Harris, 1970) molecules, and compared (Politzer, 1966) the forces for the H2 molecule calculated from various wave functions. Clinton and Hamilton (1960) examined force curves for the excited and ionized states of 02, 02+, and NO in relation to the Clinton-Rice reformulation (Clinton and Rice, 1959) of the Jahn-Teller effect (Jahn and Teller, 1937). Curtiss et al. (1975) studied ionic binding (see also, Bader and Henneker, 1965) in a series of alkali halides using the density distribution and the Berlin diagram (Berlin, 1951). 

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