Electron binding energies from collisional activation of metal-cluster dianions

Abstract

Gold-cluster dianions Au 2− n , n = 21-31, have been investigated by use of multi-collisional excitation in a Penning trap. At low excitation energies the corresponding singly charged cluster anions have been observed, but no fragments, which indicates the emission of one electron. The binding energy of the surplus electron is deduced from the dianion yield observed as a function of the collision energy by use of a statistical model based on detailed balance. The resulting binding energies of the second electrons are in good agreement with a simple liquid-drop model with empirical corrections including the Coulomb barrier. The double difference of these energies shows a strong odd-even staggering which is compared to the behavior of the electron affinity of neutral gold clusters.

Two-electron emission after photoexcitation of metal-cluster dianions

“…In addition, monomer evaporation from anionic gold clusters was described using this approach [28]. The resulting monomer dissociation energies and electron binding energies were comparable to the expected LDM values and in reasonable agreement with those extrapolated from cationic cluster data [13,14,28]. Therefore, the decay rates as given by equation (16) can be assumed to provide useful estimates for the decay processes studied in this work (single-electron emission and monomer evaporation).…”

“…T D is the temperature of the daughter system and ρ D and ρ P are the level densities of the daughter and parent system, respectively. In the case of dianionic gold clusters this decay-rate model has been used to describe thermionic electron emission after photoexcitation of Au 2− 29 [13] and electron emission from gold-cluster dianions after collisional activation [14]. In addition, monomer evaporation from anionic gold clusters was described using this approach [28].…”

“…In the meantime, the field of multiply charged metal clusters has been extended by the introduction of methods for producing higher negative charge states for metal clusters, in particular by the technique of 'electron bathing' in Penning traps [6][7][8]. Several investigations have been performed, mostly with respect to the production of such species [9][10][11][12], but also with respect to their stability and decay pathways [13,14]. While the charge-state reduction of cations is always accompanied by the loss of one or several atoms (for monovalent metals, Table 1.…”

Abundances of Tetra-, Penta-, and Hexa-Anionic Gold Clusters

“…For the large cluster sizes under investigation (n > 100), only resonantly buffer-gas cooled species are stored, in contrast to previous investigations of smaller clusters, where subsequent ion selection steps were required. 26 Production of multiply negatively charged clusters was realized by the electron-bath technique. 51,52 An electron source, located downstream the axis of the cylindrical Penning trap and just outside the super-conducting magnet, provides an electron-beam pulse (20 ms) along the magnetic-field axis.…”

“…24 In addition, delayed electron emission was observed for photoexcitation of doubly negatively charged metal clusters. 25,26 Electron emission plays an important role for the stability of small gas-phase poly-anionic systems, which have attracted scientific interest of chemists and physicists for a long time. 27,28 Due to their mutual repulsion, the maximum number of excess electrons carried by e.g.…”