For the coaxial internal rotator with rectangular potential function and freely variable valley breadth at constant periodicity, conditions are specified for an infinite number of points at which the borders of consecutive bands of energy levels must be exactly degenerate. As the valley breadth is changed through a degeneracy, the level of one symmetry relative to the potential function moves from the upper to the lower band of energy levels, or vice versa.It follows that in the rotational region above the potential maximum the levels at the band limits can repeatedly cross and rehyphen;cross when the potential maximum is increased with all other factors constant.Similar behavior will presumably occur with other potential functions.
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