Observation of ions of ~30–50 charge in a laser plasma

Spectroscopic methods were used to detect Y, Zr, Nb, Mo, Ta, and W ions of charge ~30–50 in a laser plasma interacting with a laser beam of 5×10¹⁴ W/cm² density. Spectra of neonlike ions Y₃₉²⁹⁺, Zr₄₀³⁰⁺, Nb₄₁³¹⁺, and Mo₄₂³²⁺ were identified. The presence of Ta and W lines in the 0.55–0.60 nm range yielded the ionization potential of ~4.2–5.2 keV, which corresponded to an ionic charge from 48 to 54. The intensities of the spectral lines were used to estimate the total number of ions created by one laser pulse and this number was at least 10¹¹.