Production of neutral atoms by pulsed laser heating

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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.