K-Shell Photodetachment of Excited C$^{-}$

Photodetachment of K-shells of negative ions have been of significant interest, both experimentally and theoretically [1-3], with a variety of new phenomenology uncovered. The phenomenology is due largely to the elastic and inelastic collisions suffered by the inner-shell photoelectron in exiting the system through the electron cloud formed by the outer-shell electrons. It is, thus, of interest to investigate how the K-shell photodetachment is changed when the outer-shell electron cloud is altered, i.e, when the negative ion is in an excited state. C$^{-}$ is one of the few negative atomic ions with a bound excited state. The ground state is 1s$^{2}$2s$^{2}$2p$^{3} \quad ^{4}$S and the excited state is the $^{2}$D multiplet of the same configuration. Calculations of the photodetachment cross section for this excited state of C$^{-}$ have been performed and compared with previous work on the ground state of C$^{-}$ [4,5]. Significant differences are found. This work was supported by DOE, NSF, NASA and IDRIS. [1] N. Berrah, \textit{et al}, Phys. Rev. Lett. \textbf{87}, 25300 (2001). [2] N. Berrah, \textit{et al}, Phys. Rev. Lett. \textbf{88}, 093001 (2002). [3] H. Kjeldsen, \textit{et al}, J. Phys. B \textbf{34} L353 (2001). [4] H.-L. Zhou, S. T. Manson, L. VoKy and A. Hibbert, Bull, Am. Phys. Soc. \textbf{48}, 97 (2003). [5] N. D. Gibson, \textit{et al}, Phys. Rev. A \textbf{67}, 030703 (2003).