X-ray spectral line coincidences between fluorine K- and transition-metal L-series lines

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Abstract
X‐ray spectroscopy was performed in the 12–15‐Å region, recording L‐series lines from selected laser‐irradiated transition metals. Line coincidences and near coincidences were identified between Cr, Mn, Fe, and Ni L spectra, and F viii and F ix K‐shell lines. Wavelengths were determined to accuracies of 1–3 mÅ and will be utilized in selecting potential pumping candidates in future x‐ray lasing schemes. High‐resolution x‐ray spectra were collected under controlled illumination and target conditions, using 1.05‐ and 0.527‐μm laser excitation with the KMS CHROMA laser. Laser intensity varied from 1.2–2.5×1014 W/cm2 in 200‐ps pulses. Three groups of x‐ray spectra were collected with highly dispersive x‐ray crystals at wave bands centered at 12.643, 13.781, and 14.458 Å, corresponding to H‐ and He‐like lines from fluorine. Two specially designed flat crystal spectrographs employing camera shutters were used with pairs of beryl and thallium acid phthalate (TAP) crystals. The spectra from potential lasant and pump candidates could be recorded on the same spectrogram to aid in identifying x‐ray line coincidences. In cases where wavelengths were measured in both the 1.05‐ and 0.527‐μm laser work, agreement within 1–3 mÅ was obtained for the L‐series x‐ray lines. Within this accuracy range, some five L‐series x‐ray lines, mostly 2p‐3d transitions from the metals Cr, Mn, and Ni, had wavelength values coincident with K‐series lines in fluorine.