Ions and ion-energy spectra of a collisional laser plasma produced from multi-species targets of aluminium and titanium

Experimental measurements on angular distribution of ions and ion-energy spectra from planar slab targets of Al, Ti and binary targets of Al, Ti with different stoichiometries are reported. The plasma was produced by a 125 mJ, 5 ns, 1.06 µm Nd:YAG laser, incident on a planar target at a fixed angle of −45°. The laser was focused on an ablation area of about 0.3 mm2 at a laser intensity of about 1010 W cm−2. The characteristics of the ions were obtained using a retarding-potential analyser and a quartz crystal. Results on time-of-flight spectra, ion fractions, average ionization, angular distributions of particles and their kinetic energy are presented. Full width at half maximum of the angular distributions was obtained and the results are discussed. Measurements on total integrated energy per particle are also reported. They show evidence of energy transfer from light to heavy particles in agreement with the theoretical simulation results of earlier workers. Ion acceleration due to an in-built electrostatic potential is discussed in detail and its effect was found to be marginal.