Distortion vibrational

The electron-spin time-correlation functions of Eq. (56) were evaluated numerically by constructing an ensemble of trajectories containing the time dependence of the spin operators and spatial functions, in a manner independent of the validity of the Redfield limit for the rotational modulation of the static ZFS. Before inserting thus obtained electron-spin time-correlation functions into an equation closely related to Eq. (38), Abernathy and Sharp also discussed the effect of distortional/vibrational processes on the electron spin relaxation. They suggested that the electron spin relaxation could be described in terms of simple exponential decay rate constant Ts, expressed as a sum of a rotational and a distortional contribution ... 

We are able to identify the three most important vibrations contributing to the JT distortion, vibrations 1, 3 and 6, in agreement with previous studies [5,6]. Comparing our results to the experimental one we may note that vibrations 3 and 6 are contributing approximately the same amount to the Ejy- While the other authors considered only those three normal modes, in our model all vibrations that can contribute to the JT distortion are included. Our model is completely theoretical without... 

Vibrations 1, 3, 6 contribute 90% to the JT distortion. Vibrations 2 and 5, which correspond to the e irreps in Dsh around 10%. They are JT active in the second order, and accordingly not negligible. This is because the vibrations are all of the same type, in plane ring deformation, as the ones corresponding to the e, C-C-C bend and C-C stretch, thus influencing the C-C bonding in a similar way. 

A series of n-alkylbenzenes, cooled by supersonic expansion and excited to what are initially well localized ring distortion vibrations within the first excited singlet states, show fluorescence spectral behaviour that is dependent upon the alkyl chain length. For the first three members of the series (toluene to n-propylbenzene) resonance fluorescence from the initially pumped mode in 5, was observed, but for... 

Small asymmetric distortion of the adiabatic potential minima through a weak Jahn-Teller effect the stabilization-energy away from trigonal symmetry (ca. 0.013 eV) is considerably less than the zero-point energy of the distorting vibration [4],... 

Rotational Spectroscopy Centrifugal Distortions Vibrations in Molecules... 

The constants c, that arc generated by the expansion of Equation 6-60 can be assigned to the various physical constants such as the first anharmonicity, centrifugal distortion, vibration-rotation coupling, and so on. 

At 321 mn there is a vibronic origin marked This has one quantum of v, the antisynnnetric C-H stretching mode, in the upper state. Its intensity is induced by a distortion along This state has B2 vibrational symmetry. The direct product of B2 and A2 is B, so it has B vibronic syimnetry and absorbs x-polarized light. One can also see a 4 6,, vibronic origin which has the same syimnetry and intensity induced by... 

If there is only significant overlap with one excited vibrational state, equation (Bl.2.11) simplifies fiirther. In fact, if the mitial vibrational state is v. = 0, which is usually the case, and there is not significant distortion of the molecule in the excited electronic state, which may or may not hold true, then tire intensity is given by... 

Van der Waals complexes can be observed spectroscopically by a variety of different teclmiques, including microwave, infrared and ultraviolet/visible spectroscopy. Their existence is perhaps the simplest and most direct demonstration that there are attractive forces between stable molecules. Indeed the spectroscopic properties of Van der Waals complexes provide one of the most detailed sources of infonnation available on intennolecular forces, especially in the region around the potential minimum. The measured rotational constants of Van der Waals complexes provide infonnation on intennolecular distances and orientations, and the frequencies of bending and stretching vibrations provide infonnation on how easily the complex can be distorted from its equilibrium confonnation. In favourable cases, the whole of the potential well can be mapped out from spectroscopic data. 

An important area that has yet to be fully explored is the effect of the flexibility of water molecules. The intennolecular forces in water are large enough to cause significant distortions from the gas-phase monomer geometry. In addition, the flexibility is cmcial in any description of vibrational excitation in water. 

It was shown by several workers that in this case the first-order Jahn-Teller distortion is due to an ej vibration, and that the second-order distortion vanishes. Therefore, in terms of simple Jahn-Teller theoi, the moat around the symmetric point should be a Mexican hat type, without secondary minima. This expectation was borne out by high-level quantum chemical calculations, which showed that the energy difference between the two expected C2v structures ( A2 and Bi) were indeed very small [73]. 

Figure 25 shows the results of the 2 distortion induced by a degenerate e 2 vibration that removes the Dsa degeneracy (compare Fig. 23). By symmetry, five...

Figure 29, The effect of the phase-preserving component of the degenerate 2 distorting mode, It may be regarded as a major component of the reaction coordinate that leads to the A] structure (going left, one phase of the mode). Going right, the other phase of the same vibration, the B2 state is formed. (A type-V structure is also obtained along the same coordinate).

The coordinates of interest to us in the following discussion are Qx and Qy, which describe the distortion of the molecular triangle from Dy, symmetry. In the harmonic-oscillator approximation, the factor in the vibrational wave... 

One reason for these difficulties is that metals have fairly soft bonding. This means that there is a nearly continuous range of values experimentally observed for any given metal-organic bond length. Likewise, inorganics more often exhibit distorted or fiuxional bond angles. There is also less vibrational data available to parameterize force constants. 

Katritzky and Topsom have reviewed the information available, largely from infrared and n.m.r. studies, concerning the distortion of the tt-electron system in the benzene ring brought about in the ground state by substituents. Of particular interest is the observation that both n.m.r. studies (of m- F and chemical shifts) and infrared investigations (of the intensities of bands due to certain skeletal vibrations) suggest that the value of Taft s [Pg.226]

The distortion caused by the field allows an electron to pass from the molecule to the tip if the applied potential is positive or from the tip to the molecule if the potential is negative. This is called field ionization (FI), and the electron transfer occurs through quantum tunneling. Little or no vibrational excitation occurs, and the ionization is described as mild or soft. 

The centrifugal distortion constant depends on the stifthess of the bond and it is not surprising that it can be related to the vibration wavenumber co, in the harmonic approximation (see Section 1.3.6), by... 

The vibrational dependence of the centrifugal distortion constant is too small to concern us further. 

The approximate symmetry of the band is due to the fact that Bi — Bq, that is, the vibration-rotation interaction constant (Equation 5.25) is small. If we assume that B = Bq = B and neglect centrifugal distortion the wavenumbers of the i -branch transitions, v[i (J)], are given by... 

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