  Single-particle resonant states in spherical nuclei are studied by an
analytic continuation in the coupling constant (ACCC) method within the
framework of the self-consistent relativistic mean field (RMF) theory. Taking
the neutron resonant state $\nu 1g_{9/2}$ in $^{60}$Ca as an example, we
examine the analyticity of the eigenvalue and eigenfunction for the Dirac
equation with respect to the coupling constant by means of a $\pade$
approximant of the second kind. The RMF-ACCC approach is then applied to
$^{122}$Zr and, for the first time, this approach is employed to investigate
both the energies, widths and wave functions for $l\ne 0$ resonant states close
to the continuum threshold. Predictions are also compared with corresponding
results obtained from the scattering phase shift method.
