X-ray spectra of B- and Be-like chromium in the 13–15-Å region

Improved spectroscopic techniques have yielded high-resolution L-series spectra for Cr. A focused-laser beam was used to generate the plasma source emission. The spectra, collected in two separate spectrograph settings, were identified with the aid of theoretical atomic-structure calculations as 2p–3d transitions in B- and Be-like Cr xx and xxi. Distinct spectral lines were classified by using isoelectronic sequence plots.