Hermite function solutions of the Schr\"odinger equation for the sextic oscillator

We examine the conditions under which the solution of the radial stationary Schr\"odinger equation for the sextic anharmonic oscillator can be expanded in terms of Hermite functions. We find that this is possible for an infinite hierarchy of potentials discriminated by the parameter setting the strength of the centrifugal barrier. The $N$'th member of the hierarchy involves $N$ solutions for $N$ generally different values of the energy. For a particular member of the hierarchy, there exist infinitely many bound states with square integrable wave functions, written in terms of the Hermite functions, which vanish at the origin and at infinity. These bound states correspond to distinct values of the parameter setting the strength of the harmonic term. We also investigate connection with the polynomial solutions of the sextic oscillator obtained from the formalism of quasi-exactly solvable potentials.