  All available experimental data on the spectrum of singly ionized carbon have
been critically analyzed. Measurement uncertainties of all published studies
have been re-assessed. The scope of observational data includes laboratory
emission spectra of arcs, sparks, electrodeless discharges, and hollow cathode
lamps recorded with grating and Fourier transform spectrometers, laboratory
photoabsorption spectra, and emission spectra of planetary nebulae. The total
number of observed spectral lines included in this compilation is 597. These
lines participate in 972 transitions. From this list of identified transitions,
we have derived a set of 414 energy levels, which are optimized using a
least-squares fitting procedure. The identifications are supported by
parametric calculations with Cowan's codes. The existing tables of critically
evaluated transition probabilities have been extended with our newly calculated
data. The ionization energy has been derived from the newly optimized energy
levels with improved precision. Data on isotope shifts and hyperfine structure
have also been compiled.
