Formation of a long-lived plasma bubble upon laser-induced evaporation of a metallic target into a dense gas

Summary form only given. The interaction of laser radiation with solid-state targets has long been the subject of investigation, including the case when the target is surrounded by a gas. The availability of high-power pulsed excimer lasers and the interest associated with possible technological applications have given a new force to the study of the action of UV radiation on solid-state targets in a dense gas. In this paper, we report on the formation of a long-lived (10-50 /spl mu/s) plasmoid near the surface of a metallic target. Two types of XeCl lasers were used in the experiment: "Foton-2" and "Lida-101". The chamber with targets was filled with different gases-air, helium, xenon, and others under variable pressures in the range p=10/sup -2/-760 Torr. The emission of plasma expanding into the vacuum was observed during 1 to 2 /spl mu/s. With the increase of the surrounding gas pressure the character of luminescence changed: the duration of plasma luminescence increased; the area of plasma luminescence as a rule aid not expand after the first 1 to 2 /spl mu/s; and we observed the detachment of a plasmoid from the target surface. The detached plasmoid preserved its shape and structure for a comparatively long time (up to 10 /spl mu/s in helium and up to 50 /spl mu/s in xenon and in air). More precisely, the plasmoid and the target luminescence area were separated by a dark intermediate area. The plasmoid may have a spherical or a much more complicated shape.