Rotational of symmetric top molecules

Hindered rotation of symmetric top molecules Preliminary remarks... 

Ref. p. 224] 2.8.2.1 Hindered rotation of symmetric top molecules Preliminary remarks... 

St. Pierre A. G., Steele W. A. Collisional effects upon rotational correlations of symmetrical top molecules. J. Chem. Phys. 57, 4638-48 (1972). 

The above results may be extended to electronic transitions in the case of symmetric top molecules [156, 374, 402], where, in molecule-fixed coordinates, the rotational state of the molecule is characterized by two values, namely the modulus (J) of the total angular momentum, and the projection (K) of the momentum J on the symmetry axis of the molecule (the x-axis see Fig. 1.4). In the case of an electronic transition where... 

In a certain respect the einalysis of the rotational Zeeman effect may appear simpler in the case of symmetric top molecules as compared to the asymmetric top case, since the angular momentum eigenfunctions with K... 

Fig. III. 14. The effect of the translational Zeeman effect on the absorption spectra of symmetric top molecules moving at different velocities perpendicular to the exterior magnetic field is shown for the J = - J = 2, K =l rotational transition of methylacethylene (l Oj. = 0, 100, 200,. 800 m/sec). With increasing velocity the aligning force of the Lorentz cross field...

Symmetric Top, Ia - Iq (prolate top) or Ia=Ibrotational spectrum is still degenerate in the nij quantum number however, part of the k degeneracy is lift. Only those levels with k =0 are now doubly degenerate (in k). The rotational spectrom of symmetric top molecules (such as NH3, CgHg) can be written as... 

In favorable cases, the analysis of the rotational spectrum of symmetric top molecules in vibrational state Vi... Vy... t)3N-6 allows the determination of the constants listed in this table. The rotation-vibration interaction constants are determined by the analysis of at least two vibrational states of the same normal vibration. 

The tables of thermodynamic functions have been extended by Li and Pitzer to include internal rotation of symmetric tops having very low moments of inertia. These extended tables were calculated for two coaxial symmetric tops, though they are expected to apply to molecules containing symmetric tops attached to a rigid frame of any symmetry. 

Thermodynamic calculations have been reported for several molecules containing both symmetric and asymmetric tops attached to a rigid frame. With the exception of propane-2-thiol, contributions from the internal rotation of symmetric tops have been calculated using procedures discussed on p. 288 and they are not further discussed here. Barrier heights for the... 

Many applications of Kilpatrick and Pitzer s procedure for calculating thermodynamic properties of molecules with compound rotation have been reported. In all cases possible potential energy cross-terms between rotating tops have been neglected. Contributions from internal rotation of symmetric tops have been calculated using the appropriate tables." These tables have also been used in calculations for the internal rotation of asymmetric tops hindered by a simple -fold cosine potential. 3-Fold potential barriers have been assumed in calculations for the —OH rotations in propanol and 1-methylpropanol, the —SH rotations in propane-1-thiol, butane-2-thiol, 2-methylpropane-l-thiol, and 2-methylbutane-2-thiol, the C—S skeletal rotations in ethyl methyl sulphide, diethyl sulphide, isopropyl methyl sulphide, and t-butyl methyl sulphide, and the C—C skeletal rotations in 2,3-dimethylbutane, and 2-methylpropane-l-thiol. 2-Fold cosine potential barriers have been assumed in calculations in the S—S skeletal rotations in dimethyl disulphide and diethyl disulphide. ... 

St. Pierre AG, Steele WA (1972) Collisional effects upon rotational correlations of symmetric top molecules. J Chem Phys 57(ll) 4638-4648... 

Lascombe J, Besnard M, Maraval P (1982) A new extended diffusion-model for rotational motion of symmetric-top molecules in the liquid-phase. Chem Phys 72(1-2) 177-184. doi 10.1016/0301-0104(82)87078-x... 

In favorable cases, the analysis of the rotational spectrum of symmetric top molecules in vibrational state... 

Spherical-Top Molecules The rotational energy expression of symmetric-top molecules is the same as that of a linear molecule. However, it has to be noted that, even if the energy... 

L b) rotational g-values of symmetric top molecules referred to directions perpendicular to and along the molecular axis... 

Child, M.S. and Longuet-Higgens, H.C. (1961) Studies of the (ahn-Teller effect. 111. The rotational and vibrational spectra of symmetric-top molecules in electronically degenerate states. Phil. Trans. R. Soc. Land., A 254, 259. 

The selection rules for the rotational spectra of symmetric top molecules are as follows. Note that the degenerate rotational quantum number Mj can now change as a result of a transition. 

Although the hypergeometric functions are useful in spectroscopy, as they describe the rotation of a symmetric top molecule (Section 9.2.4), their importance is primarily due to their generality. If, for example, a = 1 and fi say, Eq. (154) becomes a +i — a for all values of n. The result is the ordinary geometric series... 

A small step rotational diffusion model has been used to describe molecular rotations (MR) of rigid molecules in the presence of a potential of mean torque.118 120,151 t0 calculate the orientation correlation functions, the rotational diffusion equation must be solved to give the conditional probability for the molecule in a certain orientation at time t given that it has a different orientation at t = 0, and the equilibrium probability for finding the molecule with a certain orientation. These orientation correlation functions were found as a sum of decaying exponentials.120 In the notation of Tarroni and Zannoni,123 the spectral denisities (m = 0, 1, 2) for a deuteron fixed on a reorienting symmetric top molecule are ... 

Hougen, J. T. (1962), Classification of Rotational Energy Levels for Symmetric-Top Molecules, 7. Chem. Phys. 37, 1433. 

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