TIME-OF-FLIGHT MASS SPECTROSCOPIC STUDIES ON THE LASER-ABLATION PROCESS

The time-of-flight (TOF) measurements for ions in the expanding plume during laser ablation of Y1Ba2Cu3Ox are performed. The TOF spectra con sist of peaks of only the monatomic ions. The drift velocities for the se ions are revealed to be (2-4) X 10(6) cm/s at the laser fluence of 2.0 J/cm2 and an oxygen pressure of 10(-3) Torr. These velocities are affected by the ablation conditions, and are found to increase with in creasing laser fluence and decrease with increase of oxygen pressure. The velocity distributions for the ions at high oxygen pressure are de scribed by the supersonic expansion model with a distribution width na rrowing with decreasing oxygen pressure.