Berry rotation

Fig. 2.12 Depiction of the pseudorotation or Berry rotation 2C1 - 1 4 square-pyramidal transition state 2...

Berry rotation has to be prevented, usually by performing the experiment at lower temperatures. 

Note In a trigonal bipyramidal geometry, two different coupling constants are only observed at temperatures low enough for Berry rotation not to occur. 

Fig. 4.6 The two distinct coordination sites in a trigonal bipyraraide and then-rapid exchange through Berry rotation...

Non-rigidity has important consequences for the rotation and vibration spectra. Extensive experimental investigations exist in this domain they are based on the elaboration of model hamiltonians to describe the external motions. Recently, non-rigid molecule effects on the rovi-bronic levels of PF5 have been examined , so leading to the prediction of the spectroscopic consequences of Berry processes. 

C. Pseudorotation.—An alternative intramolecular exchange process to Berry pseudorotation has been suggested, which also occurs with conservation of angular momentum. It has been called a turnstile-rotation process because it involves the rotation of an apical-radial pair of ligands... 

Even more complex experiments have been performed on matrix isolated Fe(C0)4, generated by UV photolysis of Fe(C0)5. Isotopic labelling coupled with CW-CO laser pumping (65) of the CO stretching vibrations ( 1900 cnrl) showed that the rearrangement mode of Fe(C0)4 follows an inverse Berry pseudo-rotation as shown in Figure 8. 

Fig. 7. Structures of five-coordinate Cu2+ from first principles molecular dynamics. A Berry twist mechanism for the interconversion of the two structures is shown (from left to right) the reorientation of the main axis of a square pyramidal configuration by pseudo-rotations via a trigonal bipyramidal configuration. The grey atoms in the plane of the trigonal bipyramid are all candidates for becoming apical atoms in a square pyramid.

Bernoulli principle, 11 656-657 Berry pseudo-rotation, 16 62 Bertrandite, 3 638, 640-641 Bertrand lens, 16 470-471 Beryl, 3 638, 640 color, 7 329... 

C. Comparison of the Turnstile Rotation and Berry Pseudorotation Processes... 

The potential energy surface displayed in Figures 5a and 5b shows that there is no potential energy barrier between the square pyramid at A = >B = 101.3° and the two trigonal bipyramids situated at the two minima. Movement along the reaction coordinate connecting the two trigonal bipyramids is usually described as the Berry pseudo-rotation.13... 

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