Relative ion expansion velocity in laser-produced plasmas

The spectra of highly ionized titanium, Tixiii through Tixxi, and Cvi Lyman lines were excited in laser-produced plasmas. The plasma was produced by uniformly irradiating spherical glass microballoons coated with thin layers of titanium and parylene. The 24-beam Omega laser system produced short, 0.6 ns, and high intensity, 4×1014 W/cm,2 laser pulses at a wavelength of 351 nm. The measured wavelength for the 2p-3s Tixiii resonance lines had an average shift of +0.023 Å relative to the Cvi and Tixx spectral lines. No shift was found between the Cvi, Tixix, and Tixx lines. The shift is attributed to a Doppler effect, resulting from a difference of (2.6±0.2)×107 cm/s in the expansion velocities of Tixix and Tixx ions compared to Tixiii ions.