Ion emission characteristics from laser-produced plasmas with steep density gradients

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Abstract
Ion emission from laser-produced plasma with small focal spots (20 μm) has been investigated for s- and p-polarization of the Nd–YAG laser at IL = 6 * 1013 W/cm2. The target has been Plexiglas (Hg, C5, O2) n, and the ion analysis has been charge, mass and velocity resolved for emission angles between 15° and 65°. It is found that additional resonance absorption mainly leads to an enhancement of the number of totally emitted ions which is essentially uniform for a large region of the velocity spectrum. The total increase in plasma expansion energy is by a factor of more than 3·5. The relatively low enhancement of the average initial temperature produces an unexpected asymptotic charge distribution with higher charges if resonance absorption is not present.