Orientation effect in Ar dimer fragmentation by highly charged ion impact

Abstract

The fragmentation experiment on doubly and triply ionized Ar dimers is carried out using 1.0 MeV Ne 8+ impact, focusing on the angular distribution of Ar + and Ar 2+ ions. For the fragmentation of (Ar 2 ) 2+ , one-site double ionization and two-site double ionization are distinguished clearly, and different angular distributions are observed for these two channels. This phenomenon is explained qualitatively in simple geometrical considerations. For the fragmentation of (Ar 2 ) 3+ , we find that the Ar + ions tend to fly along the projectile direction, while the doubly charged Ar 2+ ions tend to fly in the opposite direction. This result suggests that, to form the parent ion (Ar 2 ) 3+ , transfer ionization is favorable in the first collision step, while single ionization is dominant in the second collision step.

Doubly charged dimers and trimers of heavy noble gases

“…The presence of a fleeting Ar 2 2+ has been inferred from the observation of high-energy fragment ions but intact Ar 2 2+ has never been detected. [12][13][14][15][16][17][18][19][20] Ar 2 2+ has a local minimum in the potential energy curve (PEC) at about 2 Å but this quasi-bound region cannot be reached by vertical ionization of Ar 2 which has an internuclear distance of 3.76 Å. [21][22][23] The processes following core-level excitation in krypton and xenon clusters have been studied by similar techniques.…”