a labeled configuration that is similar to the original labeled configuration, they belong to the same high probability region. Such a situation occurs when two nuclei are equivalent in the structure, which is illustrated in Figure . Therefore, finding high-probability regions Figure : Visualization of equivalence of identical nuclei. a) In ethanol, the permutation P 14 exchanges the labels of the hydroxy proton and a methyl proton. There is no rotation that maps these two protons onto each other and leaves the coordinate vector unchanged, i.e., they are inequivalent. b) In water, the permutation of the two proton positions can be undone by applying a 180°rotation, i.e., they are equivalent.