Generation of Multicharged Krypton Ions in Nanosecond Laser Ionization of Krypton Beam

Up to Kr17 + multicharged krypton ions have been observed in time-of-flight mass spectrum by a 25 ns Nd-YAG 1. 064 μm laser at laser intensity about 1012 W/ cm2 . Experimental results indicate that the multicharged ions appear only when the laser interacts with the middle part of the pulsed beam，and the intensities of the multicharged ions increase dramatically by increasing the backing pressure of Kr gas，which indicates that the clusters in the beam is essential to the production of multicharged ions. From the experimental results，it is concluded that the cluster is ionized via multiphoton ionization and forms a nanoplasma ball，which can absorb the laser resonantly to further ionize the single charge ion to the high charge state.