  We study the acceleration of heavy nuclei at SNR shocks taking into account
the process of ionization. In the interstellar medium atoms heavier then
hydrogen which start the diffusive shock acceleration (DSA) are never fully
ionized at the moment of injection. We will show that electrons in the atomic
shells are stripped during the acceleration process, when the atoms already
move relativistically. For typical environment around SNRs the dominant
ionization process is the photo-ionization due to the background galactic
radiation. The ionization has two interesting consequences. First, because the
total photo-ionization time is comparable to the beginning of the Sedov-Taylor
phase, the maximum energy which ions can achieve is smaller than the standard
result of the DSA, which predict $E_{\max}\propto Z_N$. As a consequence the
structure of the CR spectrum in the {\it knee} region can be affected. The
second consequence is that electrons are stripped from atoms when they already
move relativistically hence they can start the DSA without any pre-acceleration
mechanism. We use the linear quasi-stationary approach to compute the spectrum
of ions and electrons accelerated after being stripped. We show that the number
of these secondary electrons is enough to account for the synchrotron radiation
observed from young SNRs, if the amplification of the magnetic field occurs.
