K-shell photoabsorption spectrum of C ii

The K-shell photoabsorption spectrum of C ii has been obtained with a technique using two laser-produced plasmas. Both the discrete spectrum as well as the photoionization continuum have been observed. Precise wavelength measurements and atomic structure calculations have been performed. The discrete lines have been identified and correspond to transitions of the 1s inner electron starting from the ground or low excited levels. The 1s²2s²2p-1s2s²2pnp series has been observed up to n=6. The limits were estimated as 2 549 000 cm^-1 (316.0 eV) and 2 570 000 cm^-1 (318.6 eV) and checked against the corresponding C iii levels. The relative photoionization cross section from the threshold, at about 318 eV, up to 500 eV, has also been measured.