We present details of an experimental facility developed for the diagnostics of highly charged ions produced during pulsed laser ablation of solid targets. A range of laser fluences (2–10 J cm−2) from a Q-switched Nd : YAG laser (wavelength = 1064 nm, pulse duration ∼10 ns) was used to generate a copper plasma. The ion diagnostics were based on the time-of-flight (TOF) methods; an ion collector and a 45° parallel plate electrostatic ion energy analyser were used. A channel electron multiplier located 1.31 m away from the Cu target was used to record the energy-resolved TOF ion spectrum. The effect of laser fluence on the total ion charge, average ion energy and charge state distribution was investigated. The estimated threshold fluence for the onset of the plasma was 2.5 J cm−2. About four times increase in both average ion energy and total ion charge was observed in the investigated laser fluence range. The maximum attainable charge state of the Cu ions increased from 1+ to 7+ with the increase in laser fluence. The correlation between relative abundance of the various ion charge states indicated that the formation of Cu n+ occurred through ionization from Cu(n−1)+ by the impact of fast electrons or by multiphoton interactions.

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Chemically pure colloidal suspensions of silver and gold nanoparticles were synthesized by nanosecond pulsed laser ablation of metal plates placed in the ultrapure water. The nanoparticles were analyzed by UV-Vis spectroscopy and electron microscopy. The absorption spectra of silver and gold nanoparticles were basically the same as that of the chemically prepared nanoparticles. The diameter of almost spherically shaped Ag and Au nanoparticles prepared by 40 mJ laser energy was in the range of approximately 20–100 and 20–50 nm, respectively. The microdrops of Ag and Au colloidal solution were deposited on the surface of soda-lime glass and copper to perform nanoparticle-enhanced laser-induced breakdown spectroscopy. The results showed that Au nanoparticles cause much higher spectral enhancement, from both glass and copper targets, as compared to that of Ag nanoparticles. For the given target, type of nanoparticle and laser fluence, the enhancement factor of various spectral lines of an element was not the same. Moreover, the enhancement factor found to decrease with an increase of laser fluence, which is explained in terms of the electric field reduction due to the flow of electrons between two adjacent nanoparticles.

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