The effect of meson and isobar degrees of freedom in $A\left(\overrightarrow{e}{,e}^{\prime }\overrightarrow{p}\right)$ and ${A(e,e}^{\prime }n)$ is studied for four-momentum transfers $Q^2$ in the range between 0.2 and $0.8\hspace{0.5em}(\mathrm{GeV}{/c)}^2$. The calculations are performed in a nonrelativistic framework with explicit $(N,\Delta ,\pi )$ degrees of freedom. For the whole range of momentum transfers under investigation the effect of the meson-exchange and isobar degrees of freedom is significant. At low missing momenta and quasielastic conditions, a tendency to reduce the ${(e,e}^{\prime }p)$ and ${(e,e}^{\prime }n)$ differential cross sections is noticed. The greatest sensitivity is found in the interference structure functions $W_{\mathrm{LT}}$ and $W_{\mathrm{TT}}.$ The recoil polarization observables, on the other hand, are moderately affected by the meson-exchange and $\Delta$-isobar currents.

• Received 26 March 1999

DOI:https://doi.org/10.1103/PhysRevC.60.034604