The electronic Schrödinger equation describes the motion of a finite number of electrons under Coulomb interaction forces in a field of a finite number of clamped nuclei. It is proved that its solutions for negative eigenvalues, below the essential spectrum, lie in the spectral Barron spaces Bˢ for s<1. The example of the hydrogen ground state shows that this result cannot be improved.
Harry Yserentant (Wed,) studied this question.