Abstract
The asymptotic behaviour of the resonances in the hydrogen Stark effect at both small and large fields is related to the high-order behaviour of the Rayleigh-Schrodinger perturbation coefficients of the two-dimensional rotationally symmetric anharmonic oscillator. For two resonances at intermediate fields exhaustive numerical results are given, which provide an excellent matching between the two asymptotic behaviours. For the anharmonic oscillator eigenvalues Rayleigh-Ritz-like approximants are used which are uniformly asymptotic in the Watson sense.