Lifetime of a K-shell vacancy in atomic carbon created by 1s → 2p photoexcitation of C<SUP>+</SUP>

Lifetimes for K-shell vacancy states in atomic carbon have been determined by measurement of the natural linewidth of the 1s → 2p photoexcited states of C⁺ ions. The K-shell vacancy states produced by photoionization of atomic carbon are identical to those produced by 1s → 2p photoexcitation of a C⁺ ion: 1s2s²2p²²D, ²P, and ²S autoionizing states occur in both cases. These vacancy states stabilize by emission of an electron to produce C²⁺ ions. Measurements are reported for the lifetime of the 1s2s²2p²²D, ²P and ²S autoionizing states of C⁺: 6.3 ± 0.9 fs, 11.2 ± 1.1 fs and 5.9 ± 1.3 fs respectively. Knowledge of such lifetimes is important for comparative studies of the lifetimes of K-shell vacancies in carbon-containing molecules, benchmarking theory, and interpreting satellite x-ray spectra from astrophysical sources such as x-ray binaries. Absolute cross sections were measured for both ground-state and metastable-state ions providing a stringent test of state-of-the-art theoretical calculations.