  In two series of high-resolution coincidence experiments at the
three-spectrometer facility at MAMI, the H(e,e'pi^+)X and D(e,e'p)X reactions
were studied to search for narrow nucleon resonances below pion threshold. The
missing-mass resolution was 0.6 to 1.6 MeV/c^2 (FWHM) in the proton experiment
and 0.9 to 1.3 MeV/c^2 in the deuteron experiment. The experiments covered the
missing-mass region from the neutron mass up to about 1050 and 1100 MeV/c^2,
respectively. None of our measurements showed a signal for narrow resonances to
a level of down to 10^-4 with respect to the neutron peak in the missing-mass
spectra.
