Mass-Resolved Velocity Map Imaging of Doubly Charged Photofragments from C60

Abstract

Mass-resolved velocity map images have been measured for C60−2n2+ and C60−2n3+ (n ≥ 1) produced by photoionization of C60 with synchrotron radiation. A four-element electrostatic compound lens system was substituted for a conventional three-element system. This produced excellent time resolution, i.e., good mass-to-charge resolution, and negligible overlap between neighboring cluster ions. The translational temperatures for the C60−2n2+ ions were estimated from their velocity map images by assuming the Maxwell–Boltzmann distributions. Moreover, the improved resolution allowed observing a two-dimensional (2D) projection of three-dimensional velocity distribution of each fragment. The 2D projection of C582+ results from convolution of a narrow velocity distribution of the C60 molecular beam and a nascent isotropic profile of photodissociated C582+.