Ultraviolet and infrared laser-induced fragmentation of free (CF3I) n clusters in a molecular beam and (CF3I) n clusters inside or on the surface of large (Xe) m clusters

Abstract

The fragmentation of free homogeneous (CF3I)n clusters in a molecular beam (n ≤ 45 is the average number of molecules in the cluster) and (CF3I)n clusters inside or on the surface of large (Xe)m clusters (m ≥ 100 is the average number of atoms in the cluster) by ultraviolet and infrared laser radiations has been studied. These three types of (CF3I)n clusters are shown to have different stabilities with respect to fragmentation by both ultraviolet and infrared radiations and completely different dependences of the fragmentation probability on the energy of ultraviolet and infrared radiations. When exposed to ultraviolet radiation, the free (CF3I)n clusters fragment at comparatively low fluences (ΦUV ≤ 0.15 J cm−2) and the weakest energy dependence of the fragmentation probability is observed for them. A stronger energy dependence of the fragmentation probability is observed for the (CF3I)n clusters localized inside (Xe)m clusters, and the strongest dependence is observed for the (CF3I)n clusters located on the surface of (Xe)m clusters. When the clusters are exposed to infrared radiation, the homogeneous (CF3I)n clusters efficiently fragment at low fluences (ΦIR ≤ 25 mJ cm−2), higher fluences (ΦIR ≈ 75 mJ cm−2) are needed for the fragmentation of the (CF3I)n localized inside (Xe)m clusters, and even higher fluences (ΦIR ≈ 150 mJ cm−2) are needed for the fragmentation of the (CF3I)n clusters located on the surface of (Xe)m clusters. It has been established that small (CF3I)n clusters located on the surface of (Xe)m clusters do not fragment up to fluences ΦIR ≈ 250 mJ cm−2. The fragmentation efficiency of (CF3I)n clusters is shown to be the same (at the same fluence) when they are excited by both pulsed (τp ≈ 150 ns) and continuous-wave infrared laser radiations. Possible causes of such a pattern of ultraviolet and infrared laser-induced fragmentation of these clusters are discussed.