In a plume produced by excimer ArF laser, the number densities of excited atoms and electrons, and the expansion velocity of ablated carbon atoms in an Ar gas were measured and compared with those obtained in vacuum. A saturation in C(3(1)P(1)(0)) density was observed as the laser fluence increased. This saturation was shown to be closely related to the electron density saturation. The excitation of Ar(4s'[1/2](1)(0)) and C(3(1)P(1)(0)) was interpreted by electron collisions and was dependent on gas pressure and excimer laser fluence. (C) 2002 Elsevier Science B.V All rights reserved.