Evidence of a nonthermal mechanism for ejection of ions and neutrals during excimer laser ablation of Ge

Resonance ionization spectroscopy combined with time of flight mass spectrometry is used to analyze the ejection of ions and neutrals from the surface of a Ge target irradiated with ultraviolet XeCl excimer laser pulses. The ejection of ions and neutrals has been observed to occur at temperatures well below the melting point of the target and, therefore, through a nonthermal mechanism that may be dominant for fluences below the threshold for visible plasma formation. Within this regime, the velocities of the ejected neutrals in the ground state are in the order of 3×104 cm/s.