Discussion on Particle Formation and Ejection of Laser Ablation for Depositing Superconducting Thin Films

<正> A new model for the particle formation and ejection of laser ablation of a target fordepositing high T_c superconducting thin films is presented,by which the two features,film composition closeto the ablated target and particle ejection along the normal of the target (?),can be explainedconveniently. The laser fluence threshold for ablation of the target,the layer (?) kness ablated by each lasershot and the recoil pressure for particle ejection normal to the target are analyzed mathematically and theirexpressions have been derived.Furthermore.the absorption coefficient of Y-Ba-Cu-O material to 308nm laserirradiation and the laser fluence threshold for ablation are measured and evaluated using the derivedexpressions.It is shown that the theoretical prediction agrees with experiment welt