Space- and time-resolved measurements of temperatures and electron densities of plasmas formed during laser ablation of metallic samples

Temperature and electron-density profiles in a laser-produced plasma have b een measured at various distances from the sample surface and different del ay times from the laser pulse. The plasma is produced with a Nd:YAG laser f ocused on a low-alloy steel sample in air at atmospheric pressure. The dete rmination of the parameters is made starting from the distinct emission spe ctra emitted by the plasma along a direction parallel to the sample surface and measured simultaneously by a CCD detector. The experimental relative e rror is 1.5% for temperatures and 4.5% for electron densities. A small spat ial variation of the plasma temperature (Delta T less than or equal to 1000 K) is obtained except for the outer regions, were the intensity is weak. A higher spatial variation is obtained for the electron density, especially at initial times (Delta N-e congruent to 10(17) cm(-3) at t = 3 mu s).