Abstract: The process of pulsed 355nm laser ablation deposition of Ta₂O₅ film in the O₂ ambient is investigated.The time-resolved quadrupole mass spectrometric measurements show that the nascent ions and neutral species produced by laser ablation of Ta₂O₅ in high vacuum are Ta⁺,O⁺,TaO⁺,TaO⁺ 2,and Ta,O,TaO,TaO₂,respectively.The measured TOF spectra indicate that the velocities of ablated ion species are faster than that of neutral species.In the O₂ ambient,emission spectra from excited ions,atoms and molecular oxides in the plume are observed.The time-resolved emission spectra of the plume at diffevent O₂ ambient pressure show that part of the excited tantalum oxid emolecules are formed from the reactive collisions of the ablated tantalum containing species with oxygen.Compositional analysis of the deposited films reveals that the reactive collisions in the gas phase and subsequent oxidation of the deposited film on the substrate are responsible for the production of the high quality Ta₂O₅ film in the oxygen ambient.