Does the electron spin affect the rates of electron tunneling in electrochemical systems?

An effect of spin degeneracy of electron energy levels in the metal electrode on the observable characteristics of electrochemical systems in the absence of magnetic field is discussed. Single-electrode outer-sphere electron transfer reactions are considered as well as redox-mediated electron tunneling in electrochemical contacts. Particular attention is paid to the difference between the spin-less model and the limit of infinitely large Coulomb repulsion of the electrons occupying the same valence orbital in the redox group. Adiabatic and non-adiabatic regimes of the transitions are studied and the expressions for the tunnel current are obtained.