  Spectra of several R Coronae Borealis (RCB) stars at maximum light were
examined for the [C I] 9850 A and 8727 A absorption lines. The 9850 A line is
variously blended with a Fe II and CN lines but positive identifications of the
[C I] line are made for R CrB and SU Tau. The 8727 A line is detected in the
spectrum of the five stars observed in this wavelength region. Carbon
abundances are derived from the [C I] lines using the model atmospheres and
atmospheric parameters used by Asplund et al. (2000).
  Although the observed strength of a C I line is constant from cool to hot RCB
stars, the strength is weaker than predicted by an amount equivalent to a
factor of four reduction of a line's gf-value. Asplund et al. dubbed this 'the
carbon problem' and discussed possible solutions.
  The [C I] 9850 A line seen clearly in R CrB and SU Tau confirms the magnitude
of the carbon problem revealed by the C I lines. The [C I] 8727 A line measured
in five stars shows an enhanced carbon problem. The gf-value required to fit
the observed [C I] 8727 A line is a factor of 15 less than the well-determined
theoretical gf-value. We suggest that the carbon problem for all lines may be
alleviated to some extent by a chromospheric-like temperature rise in these
stars. The rise far exceeds that predicted by our non-LTE calculations, and
requires a substantial deposition of mechanical energy.
