Femtosecond laser ablation of sapphire: time-of-flight analysis of ablation plume

Time-of-flight mass spectrometry has been used to investigate the mass and velocity distributions of positive ions produced on laser ablation of sapphire with ultrashort 200 fs.laser pulses at a wavelength of 790 nm. Aluminium and oxygen ions were observed with the proportion of singly and doubly charged oxygen ions increasing with increasing number of laser shots for a given laser fluence. The ions have extremely high kinetic energies which is attributed to Coulomb explosion from charged defect sites. q1998 Elsevier Science B.V.