Eur. Phys. J. D (2017) 71: 99
https://doi.org/10.1140/epjd/e2017-80015-0

Regular Article

Low-energy collisions of helium clusters with size-selected cobalt cluster ions^*

¹ East Tokyo Laboratory, Genesis Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba 272-0001, Japan
² Cluster Research Laboratory, Toyota Technological Institute: in East Tokyo Laboratory, Genesis Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba 272-0001, Japan

^a e-mai: ichihashi@clusterlab.jp

Received: 6 January 2017
Received in final form: 3 March 2017
Published online: 25 April 2017

Abstract

Collisions of helium clusters with size-selected cobalt cluster ions, Co_m⁺ (m ≤ 5), were studied experimentally by using a merging beam technique. The product ions, Co_m⁺He_n (cluster complexes), were mass-analyzed, and this result indicates that more than 20 helium atoms can be attached onto Co_m⁺ at the relative velocities of 10³ m/s. The measured size distributions of the cluster complexes indicate that there are relatively stable complexes: Co₂⁺He_n (n = 2, 4, 6, and 12), Co₃⁺He_n (n = 3, 6), Co₄⁺He₄, and Co₅⁺He_n (n = 3, 6, 8, and 10). These stabilities are explained in terms of their geometric structures. The yields of the cluster complexes were also measured as a function of the relative velocity (1 × 10²−4 × 10³ m/s), and this result demonstrates that the main interaction in the collision process changes with the increase of the collision energy from the electrostatic interaction, which includes the induced deformation of He_N, to the hard-sphere interaction.