Analyzes the coupling between a magnetic monopole’s charge-rotor degree of freedom and massless-fermion vacuum fluctuations, showing the naive dyon spectrum is replaced by excitations with vanishing electric-field expectation value — part of the theoretical derivation underlying the Callan-Rubakov catalysis effect. relevance_note: companion derivation (with Rubakov 1981) of the monopole-catalyzed baryon-decay mechanism, load-bearing for the monopole doomsday route’s theoretical validity.