Production of neutral atoms by pulsed laser heating

Abstract

Sodium and thallium surfaces were heated in vacuum by a short intense pulse from a CO2 TEA laser. The time-dependent emission of neutral atoms following the laser pulse was measured in the density range 1011–1012 atoms/cm3 by monitoring the absorption from a beam of resonance light. The temperature of the metal surface and the depth of heating after the laser pulse were obtained using a theoretical model. The results show that at the end of the laser pulse the temperature of the surface is close to the boiling point for the metal independent of laser energy in the range 106–109 W/cm2. The surface temperatures were 593 and 934 °K for sodium and thallium, respectively. The depth of heating is greater than can be explained by heat conduction alone. It is suggested that during the laser pulse the metal is heated by a shock wave. The results also point out the limitations of pulsed laser vaporization in the production of neutral atoms from refractory materials.

Low energy neutral beam production by laser vaporization of metals

“…This is due to the fact that for J > 6 J cm-2, the molybdenum absorption measurements were severely perturbed by light emission from the neutral beam itself. This effect has already been noted by Prengel et al [9] and (1) Note that in these experiments, due to the small solid angle, the optical thin conditions is satisfied. Fig.…”

“…A comparison of the results for these two neutral beams shows that the average beam energy is slightly higher for the Ni than for the Al beam. This effect is probably due to the higher boiling point of nickel [9].…”

“…The, TFR Group [7]-used the same technique to inject molybdenum atoms into the TFR plasma, in order to help in the identification of highly stripped molybdenum ion spectral lines. A few other authors have studied this neutral beam production technique [8,9], but were mainly interested in the surface conditions under laser irradiation. As a consequence, only a few quantitative data in the literature can be used when planning an impurity injection experiment on a fusion oriented plasma.…”

New Developments in Matrix Isolation Spectroscopy

“…The laser-induced plasma is extremely hot, with temperatures high above the boiling point of the sample, typically around 10 4 K, and with particle velocities exceeding 10 4 m/s. , The impact of such high-energy atoms, electrons, or ions could lead to reactions on or near the matrix surface and also cause considerable damage to the crystal lattice, leading to broadened and perturbed spectra. Thus for instance in optical absorption spectra of mass-selected ions landed with residual kinetic energies of about 50 eV, all the absorption peaks exhibited widths of some 100−150 cm -1 .…”

Analysis of Atomic Beams Produced by Laser-Induced Ablation

“…Laser-induced particle emission from solids has been studied extensively and the applications are numerous [ 1 , 2 ] . Comparatively little has been done on the production of pure atomic beams; the related experiments reported so far have been summarized by Prengel et al [3]. These authors were interested in the condition of the laser-heated surface and the production of neutral atoms after the laser pulse was over and the plasma also produced was dissipated.…”