  By exactly analyzing the spin-1/2 Luttinger liquid (LL) and numerically
solving a model of a mobile impurity electron in the LL, we obtain the
one-electron spectral function $A(p,\omega)$ in a one-dimensional (1D) metal in
an entire range of $p$ at zero temperature. For $|p|$ near the Fermi point
$p_{\rm F}$, $A(p,\omega)$ is featured by two prominent peaks of spinon and
(anti)holon representing spin-charge separation, but we also find an additional
cusp structure between them. For $|p| \gg p_{\rm F}$, this structure evolves as
a main peak in $A(p,\omega)$ by swallowing the antiholon mode and its
dispersion relation approaches the one of a free electron, implying the
existence of an electron excitation in the whole region, but not quite a
quasiparticle in the Fermi liquid due to ever existing power-law decay of the
excitation.
