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M. Holzweber, W. Linert, H. Hutter:
"Interaction of Bi Cluster Ions with Room Temperature Ionic Liquids";
Vortrag: 7th European Workshop on Secondary Ion Mass Spectrometry, Münster,; 19.09.2010 - 23.09.2010; in: "7th European Workshop on Secondary Ion Mass Spectrometry", (2010), S. 108.

Room temperature ionic liquids (RTIL) have numerous interesting physical properties such as a high thermal stability, a wide liquid range and favourable solvating properties. Besides their low melting point they also have a very low vapour pressure which enables their analysis in ultra high vacuum devices such as x-ray photoelectron spectroscopy (XPS) [1, 2] and time-offlight secondary-ion-mass-spectrometry (ToF-SIMS).[1, 3] RTILs of the imidazolium group are showing a general fragmentation pattern in both positive and negative polarity. Furthermore, the influence on enhanced secondary ion emission in dependence on the primary ion cluster size (Bin +) will be shown. Varying the counter ion is also influencing the secondary ion yield. On some ionic liquids with differing anions we will demonstrate this dependency. Solvent parameters, such as the Kamlet-Taft parameters α and β and Gutmann´s donor and acceptor numbers DN and AN [4] can principally be correlated with SIMS data.[5] This might be of importance because such parameters, although well known and adapted to "usual" solvents, are not well established for ionic liquids. Donor and Acceptor numbers for ionic liquids, based on the assumption that cations are solvated by anions and anions solvated by cations, is presented. The obtained ToF-SIMS results show a linear dependence of DN and AN with the anion yield. This in turn supports the applicability of the firstly presented DN-AN concept for ionic liquids. It is well known, that upon changing the primary ion to primary cluster ions influences the fragmentation, defined as the ratio of the summarised fragment ion yields to a quasimolecular ion yield (usually M+H or M-H), significantly. However, the interactions of primary cluster ions with liquid surfaces have so far not been studied. We will therefore discuss this behaviour on a RTIL in liquid as well as in solid (frozen) state.