Size-Dependent Electron-Impact Detachment of Internally ColdCn−andAln

Abstract

The cross sections for electron detachment of internally cold Cn- and Aln- clusters were measured using an electrostatic ion beam trap fitted with an internal electron target. The measured electron-impact detachment cross sections for the Cn- (n = 1-9) clusters exhibit even-odd oscillations reflecting the binding energy trend, namely, higher cross sections for weaker binding. Surprisingly, however, these cross sections increase on the average with cluster size, n, in spite of the increase in electron binding. In contrast, the Aln- (n = 2-5) clusters follow the known scaling laws for electron detachment. We suggest that the size-dependent polarizability of these clusters is responsible for the observed behavior.

Polarizability of Small Carbon Cluster Anions from First Principles

“…This provides clear-cut computational support to an interpretation of detachment crosssection trends in terms of polarizability. 13 It rationalizes the fact that, for carbon anions, both the detachment cross-section and the binding energy increase on average with increasing cluster size, whereas in the absence of polarization effects they should exhibit opposite trends.…”

“…An important recent example is given by electron detachment experiments, where polarization by the incident electron is believed to play an important role in the detachment process. [13][14][15] This can be understood phenomenologically by considering that electron detachment occurs mainly at the point of closest approach, where the incoming electron has minimal kinetic energy. 16 The attractive nature of the polarization potential will reduce the distance of closest approach, thus resulting in a larger distortion of the initial wave function and an enhanced electron detachment.…”

Simultaneous electrostatic trapping of merged cation & anion beams

“…Electrostatic ion storage devices offer a powerful new technology to experimentally explore the interactions of atomic, molecular and cluster ion species with neutral targets, 1,2 electrons, 1,3,4 black-body radiation 5,6 and with various laser fields. [7][8][9][10][11][12][13][14][15] The detailed understanding of the interactions and time-evolution of ionic species is important for a fundamental understanding of the underlying quantum mechanical manyelectron and many-atom dynamics, 16,17 as well as for application to studies of the chemical evolution of a broad range of partly ionized interstellar-medium, [18][19][20][21][22] planetary, atmospheric and man-made environments.…”

Sidebands from longitudinal bunch oscillations in an electrostatic ion beam trap

“…Another example is the use of pickup techniques [3], in which the induced current on an electrode is amplified and analyzed. This technique is used to monitor the relative abundance of the stored ions [4][5][6], their masses [7,8], and their lifetimes [9].…”