A comparison of the temperatures and electron densities of laser-produced plasmas obtained in air, argon, and helium at atmospheric pressure

Time-resolved measurements of temperatures and electron densities of laser- produced plasmas generated in air, argon, and helium at atmospheric pressur e are presented. The plasmas are obtained by the focusing of a Nd:YAG laser on a low-alloyed steel sample. The relative experimental error for tempera tures is in the range 0.6%-3% and for electron densities, it is 4.5%. The h igher temperatures and electron densities are obtained in argon, and the lo wer ones are found in helium. The temporal evolution of temperature and ele ctron density in the three gases is compared, showing that a faster decay o f both magnitudes takes place in helium.