Search for amplification in the far vacuum ultraviolet due to transitions of multiply charged ions in an extended laser plasma

A search was made for amplifications due to transitions in multiply charged ions in an extended plasma. This was done by investigating the spectra of plasma filaments created by subnanosecond laser pulses interacting with various targets. Anomalies were found in the behavior of the intensities of a series of Na IX and C VI lines observed along the filament axis. It was found that these anomalies could be attributed to amplification due to the 2p–4d, 2p–3d, and 2s–3p transitions in the Na IX ion and due to the 3–4 transition in the C VI ion.