Eur. Phys. J. D (2012) 66: 72
https://doi.org/10.1140/epjd/e2012-20639-x

Regular Article

Negative ion formation mechanism and velocity distribution in laser desorption/ionization of C₆₀

¹ University of IcelandDepartment of Chemistry, and Science Institute, Dunhaga 3, 107 Reykjavk, Iceland
² Interdisciplinary Nanoscience Center (iNANO), Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, 8000 Aarhus C, Denmark

^a e-mail: ibald@zedat.fu-berlin.de
^b e-mail: odduring@hi.is

Received: 2 November 2011
Received in final form: 17 January 2012
Published online: 27 March 2012

Abstract

In UV laser desorption/ionization (LDI) of C₆₀, both molecular cations and anions are formed. While the C₆₀⁺ formation has been discussed in a number of studies and is fairly well understood, the C₆₀^- formation has received less attention. Here, we present measurements of C₆₀^- and C₆₀⁺ formation and its fluence dependence in UV-LDI of C₆₀ from both metallic and non-metallic substrates. The data show clearly that the C₆₀^- formation is coupled to the C₆₀⁺ formation, indicating that C₆₀^- is predominantly formed through electron transfer early in the expanding laser desorption plume. The velocity distribution of desorbed C₆₀^- ions was also determined and was found to be best described by two Maxwell-Boltzmann distributions with superimposed stream velocities.