  The structure of $^{19,20,22}$C has been investigated using high-energy
(about 240 MeV/nucleon) one- and two-neutron removal reactions on a carbon
target. Measurements were made of the inclusive cross sections and momentum
distributions for the charged residues. Narrow momentum distributions were
observed for one-neutron removal from $^{19}$C and $^{20}$C and two-neutron
removal from $^{22}$C. Two-neutron removal from $^{20}$C resulted in a
relatively broad momentum distribution. The results are compared with
eikonal-model calculations combined with shell-model structure information. The
neutron-removal cross sections and associated momentum distributions are
calculated for transitions to both the particle-bound and particle-unbound
final states. The calculations take into account the population of the mass
$A-1$ reaction residues, $^{A-1}$C, and, following one-neutron emission after
one-neutron removal, the mass $A-2$ two-neutron removal residues, $^{A-2}$C.
The smaller contributions of direct two-neutron removal, that populate the
$^{A-2}$C residues in a single step, are also computed. The data and
calculations are shown to be in good overall agreement and consistent with the
predicted shell-model ground state configurations and the one-neutron overlaps
with low-lying states in $^{18-21}$C. These suggest significant
$\nu{s}_{1/2}^2$ valence neutron configurations in both $^{20}$C and $^{22}$C.
The results for $^{22}$C strongly support the picture of $^{22}$C as a
two-neutron halo nucleus with a dominant $\nu{s}_{1/2}^2$ ground state
configuration.
