The enthalpies of vaporisation, Δ(vap)H(298), of seven ionic liquids (ILs) (four imidazoliums, a pyridinium, a phosphonium and an isouronium) have been determined by temperature programmed desorption using line of sight mass spectrometry. They were: 1-ethyl-3-methylimidazolium bis(pentafluoroethyl)phosphinate, [C(2)C(1)Im][PO(2)(C(2)F(5))(2)]; 1-butyl-3-methylimidazolium octylsulfate, [C(4)C(1)Im][C(8)OSO(3)]; 1-butyl-3-methylimidazolium tetrafluoroborate, [C(4)C(1)Im][BF(4)]; 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [C(6)C(1)Im][FAP]; 1-butylpyridinium methylsulfate, [C(4)Py][C(1)OSO(3)]; trihexyl(tetradecyl)phosphonium tetrafluoroborate, [P(6,6,6,14)][BF(4)] and O-ethyl-N,N,N',N'-tetramethylisouronium trifluoromethanesulfonate, [C(2)(C(1))(4)iU][TfO]. The values were found to be consistent with a previously proposed, predictive, model in which Δ(vap)H(298) is decomposed into a Coulombic component (computable from the IL density) and van der Waals components from the anion and cation. Two previously predicted values of Δ(vap)H(298) were found to be within 6 kJ mol(-1) of the measured experimental values. Values for the van der Waals components are tabulated for eleven cations and twelve anions. Predictions are made for Δ(vap)H(298) for 13 ILs with as yet unmeasured Δ(vap)H(298) values (using experimental molar volumes), and for a further 44 ILs using estimated molar volumes.

Temperature programmed desorption has been used to measure the bonding of 1-methyl-3ethylimidiazolium bis [(trifluoromethyl) Au(111), and the bonding of acetone within the ionic liquid (IL) at both the liquid-vacuum and liquid-Au(111) interfaces. Multilayer evaporation the ionic liquid occurred with an activation energy of 126 AE 5 kJ mol À1 and a preexponential term of 10 16AE1 s À1 , the evaporation mechanism being the direct emission into the vacuum of an ion pair from within the liquid surface. [C 2 C 1 Im][Tf 2 N] chemisorbed to Au(111) had an activation energy for desorption which varied from 158 to 132 kJ mol À1 for a coverage change of 0 / q / 1.0.The chemisorbed layer was thought to comprise a single layer of co-planar ions at q ¼ 0.5 with dipoles parallel to the surface, and a bi-layer at q ¼ 1 with dipoles perpendicular to the surface. The acetone experiments consisted of a layer of porous ionic liquid glass deposited on top of a layer of solid acetone at 100 K. During desorption acetone was captured within the ionic under-layer of the glass with an activation energy for subsequent desorption that dropped from 54 to 43 kJ mol À1 for 0 / q / 1.0. This variation in energy is thought to be due to a range of chemical environments within the ionic under-layer.

Line-of-sight mass spectrometry (LOSMS) defines a focal area on a sample surface such that only species originating from within that area are detected by a mass spectrometer. Line-of-sight gas trajectories are established between a focal area and the ionisation volume using two apertures with cryo-pumping walls to prevent all other trajectories from reaching the ionisation volume. Because of the geometry, LOSMS is area specific, angle resolving and capable of detecting neutral, radical and charged species with approximately equal sensitivity and can be used to measure the speed distribution of gases. The history of LOSMS is reviewed, and the different aspects are drawn together to give a coherent description of the technique. The general operating principles are used to predict how a gas microscope with a spatial resolution of 25 μm and a gas camera with an angular resolution of 0.014°could be built. Three types of experiment that can be carried out using LOSMS are described: temperature-programmed desorption, sticking probability measurements and general monitoring of the gas phase above a surface where the temporal variation of the gas pressure and sample temperature can be arbitrarily complex. Procedures for accurately locating the line-of-sight focal area are described. The angle-resolving ability of LOSMS is demonstrated, showing that the angular distributions of two gases, acetone and 1,2,3-trifluorobenzene, from a solid surface (silver) and a liquid (1-ethyl-3-methylimidazolium ethyl sulfate [C 2 C 1 Im][EtSO 4 ]) surface are cosine distributions as predicted by Knudsen's cosine law. Figure 6. Illustration of how spurious peaks (I refl ) in a temperature-programmed desorption (TPD) measurement, I expt , due to gas reflecting from the surface under study may be removed using the total pressure measurement, P, to give the true desorption spectrum, I des .

Singly and doubly charged atomic ions of zinc and copper have been complexed with pyridine and held in an ion trap. Complexes involving Zn(II) and Cu(I) (3d(10)) display a strong tendency to bind with H(2)O, whilst the Zn(I) (3d(10)4s(1)) complexes exhibit a strong preference for the attachment of O(2). DFT calculations show that this latter result can be interpreted as internal oxidation leading to the formation of superoxide complexes, [Zn(II)O(2)(-)](pyridine)(n), in the gas phase. The calculations also show that the oxidation of Zn(I) to form Zn(II)O(2)(-) is promoted by a mixing of the occupied 4s and vacant 4p orbitals on the metal cation, and that this process is facilitated by the presence of the pyridine ligands.