Internal rotor asymmetric

The microwave spectram exhibits a tunnelling sphtting due to a large amphtude internal rotation of the H2O subunit that exchanges bonded and non-bonded atoms. The internal rotor states are labelled with the asymmetric rotor quantum number for the rotational levels of free water jkak. ... 

Fig. 6.2. Internal-vane, external-vane, and plunger-type rotary vacuum pumps. It will be noted that the internal-vane pump involves a rotor concentric with the drive shaft, but which is off-center with respect to the stator. By contrast, the external-vane and rotary-plunger pumps have a rotor which is asymmetric with respect to the shaft however, the shaft is centered in the stator. All three involve close tolerances, so the high-vacuum performance is impaired by particles of dirt or corrosive gases. Some pumps are partially constructed from soft die-cast metal, which is eroded by mercury. Special corrosion-resistant pumps and inert flourinated pumps are used in the semiconductor industry.

In asymmetric tops like methyl alcohol, CHjOH, and symmetric rotors like CH SiH, the methyl group can undergo internal rotation relative to the rest of the molecule, traditionally called the frame (LS59, OM07). Although various different tops are considered here, all have three-fold symmetry. In such cases, the potential l hindering the internal rotation can be written ... 

For heavy asymmetric rotors the torsional levels may be sufficiently low for thermodynamic properties to be estimated by using the classical approximation. Gwinn and Pitzer have expressed the classical approximation to the complete internal partition function as... 

The three rotational constants completely determine the energy level scheme of a rigid asymmetric top. This scheme may be considerably more complex than that of a symmetric rotor, especially if k is close to zero. Like it has already been shown for linear and symmetric-top molecttles, the mrmber of parameters reqttired to theoretically reproduce accurately measirred rotational spectra may increase considerably if effects of rotation-vibration interaction, spin coupling, or internal rotation must be taken into account. Details of practical importance will be considered below. 

The T-shaped groimd state was fitted as an asymmetric rotor with free internal rotation using the Hamiltonian... 

Internal rotation analysis can be quite complicated for molecules with asymmetric rotors and asymmetric frames such as CH2DOH. Various theoretical approaches have been developed to handle most situations. Table XVII gives a summary of barriers for various isotopic forms of CH3OH. Depending on the molecular symmetry, some... 

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