On the role of dissociative ionization in the formation of argon dimer ions

Abstract

Abstract. The formation of Ar + ions has been investigated by means of the threshold photoelectron photoion coincidence (TPEPICO) technique. Two pathways for the formation of Ar 2 ions are important. One is a direct path via excitation of Rydberg states of Ar 2 with consecutive autoionization. The other path is dissociative ionization of larger argon clusters, in this case argon trimers. These two pathways lead to Ar] ions with different internal energy. The pathways are easily distinguished in the TPEPICO-TOF spectra by the kinetic energy released (KER) in the dissociative ionization. The KER for the reaction Ar~--+Ar2 v +Ar was measured as a function of the photon energy and compared to the KER expected from statistical theory. The agreement is satisfying and confirms that Ar3 + ions do indeed dissociate at the thermochemical threshold. At higher photon energy the excited 2H (3/2)g state of Ar + is also detected from a second component in the KER. By applying a kinetic energy discrimination it is possible to measure cluster ion spectra in the presence of larger dusters but essentially without interference from the latter.

Investigation of the ArN+2 ion by dissociative ionization of argon/nitrogen clusters

“…The formation of Ar 2 ϩ by dissociative ionization of Ar 3 has been investigated in our earlier work. 5 The Ar 2 ϩ observed in this work will partly be formed by dissociative formation of Ar 3 . Here, however, part of the Ar 2 ϩ is formed by dissociative ionization of Ar 2 N 2 .…”

“…Details of the molecular beam TPEPICO spectrometer have been described in detail previously. 5,25 Only the main features will be given in this paragraph. The photon beam is obtained by dispersing synchrotron radiation from the storage ring BESSY at Berlin at the 3 m NIM1 port.…”

“…That kinetic energy release can be determined by measuring the time-of-flight mass spectra in a photoelectron photoion coincidence experiment ͑PEPICO͒. [1][2][3][4] In a recent publication 5 we have shown that the kinetic energy released in the dissociative ionization of argon trimer clusters can be measured as a function of the excitation energy. By comparison with the statistically expected KER it was then possible to obtain new information about the thermochemistry of small argon clusters.…”

Fragmentation dynamics of ionized argon clusters: an effective potential model

“…In the present work we have examined a broad spectrum of cluster sizes, and two of the most likely nucleation mechanisms, with the aim of studying the relative metastability and the range of possible relative lifetimes for ionic Argon clusters, usually formed in a supersonic expansion and subsequent ionization by either electron or photon impact [5,6,17].…”

Photoionization of Xe2, Xe3 and Xe4 in the 1024–1113 Å region

“…by Gantef6r et al [10] and Kamke et al [11] has provided important information on these species. Note, however, a recent study of ion cluster dynamics by Weitzel et al [12] indicates that fragmentation contributions are present in the dimer ion yield of argon even in the threshold region.…”