Abstract

Recent experimental results have challenged the conventional view that nanosecond pulsed laser vaporization of metals can always be ascribed to thermal mechanisms. Several studies have explored non-thermal vaporization from metals in the solid phase, using low laser fluences [1-4]. The apparent consensus is that the creation and local decay of surface plasmons (collective excitations of electrons) are responsible for discharging energetic atoms from metal surfaces [5]. However, the experimental results reported in this work demonstrate the need to rc-cvaluate existing ideas concerning thermal and electronic (plasmon) effects in pulsed laser vaporization of metals. We find that when target surfaces arc microscopically rough, yields and translational energies from irradiated metal surfaces arc greatly enhanced [6]. This is qualitatively consistent with plasmon involvement, but measured translational energies prove that some atoms are directly ejected with translational energies greater than cither the quantized plasmon energy or the photon energy. Therefore, the real situation appears to be more complex than the perception that the vaporization energy results from a single quantized surface plasmon transferring its energy to a single ion or atom.

© 1996 IEEE