  It is generally accepted that double neutrinoless electron capture is a
resonance process. The calculations of the probability of shaking with the
ionization of the electron shell occurring during the transformation of 152Gd
and 164Er nuclei are performed below. These nuclides have the lowest resonance
defect among all known nuclei, being considered as main candidates for
discovering the neutrinoless mode of the transformation. The results show
predominant contribution of the new mechanism for most of the candidate nuclei.
The value of this amendment rapidly increases with an increasing resonance
defect. Thus, in principle, double neutrinoless electron capture appears not to
be a resonance process at all.
