Angle-resolved energy distributions of laser ablated silver ions in vacuum

Abstract

The energy distributions of ions ablated from silver in vacuum have been measured in situ for pulsed laser irradiation at 355 nm. We have determined the energy spectra for directions ranging from 5° to 75° with respect to the normal in the intensity range from 100 to 400 MW/cm2. At the highest intensity and for angles close to the normal, the highest ion energy measured exceeds 500 eV. However, the energy distributions are shifted strongly towards low energies with increasing angle.

Dynamics of the plume produced by nanosecond ultraviolet laser ablation of metals

“…1͒. 19,36,37 The duration of the laser pulse was 6 ns and the fluence was 2.0 J/cm 2 corresponding to an intensity of 3.3ϫ10 8 W/cm 2 . The area of the laser beam spot was 0.041Ϯ0.005 cm 2 , but the shape was changed during the measurements of the flip-over effect.…”

Angular Distribution of Electron Temperature and Density in a Laser-Ablation Plume

“…Even at relatively low intensities near the threshold for ablation ͑0.2 1.0 GW cm 22 ͒, it is observed that the ablated material is significantly ionized [7,8], and the ions in the plasma plume have energies ranging up to several hundred eV [9]. At the end of the nanosecond laser pulse, the ablated material exists as a thin layer of plasma on the target surface.…”

“…The main outcome of our investigation was that the electron temperature varies more slowly as a function of angle than the ion energy distribution. Another important feature is that, in our intensity range, the electron temperature typically is between 0.1 and 0.5 eV, whereas the average ion flow energy is about 2 orders of magnitude larger.The ablation was done using a frequency-tripled Nd:YAG laser (355 nm) directed at normal incidence onto a silver target in a vacuum of 10 28 Torr, in the same geometry as used earlier [8,9] (Fig. 1).…”

“…Initially the expansion of the plume is primarily driven by the plasma pressure gradients [2], but there may be an additional contribution from Coulomb repulsion between the ions if there is significant net loss of the more mobile electrons [3,10]. In any case, when the plume has propagated more than a few hundred mm from the target surface, the major part of the initial thermal energy in the plasma is converted to the directed kinetic energy of the ions, which are much more massive than the electrons [11,12].The energy distribution of the ions has been measured using time-of-flight (TOF) optical spectroscopy [13,14] and ion probes [4,[7][8][9][15][16][17]. Mostly these ion probe measurements have been for the plasma flow close to the normal of the target surface.…”

“…The energy distribution of the ions has been measured using time-of-flight (TOF) optical spectroscopy [13,14] and ion probes [4,[7][8][9][15][16][17]. Mostly these ion probe measurements have been for the plasma flow close to the normal of the target surface.…”