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RATIONALE The very small clusters of the type KnF are of particular importance since their first ionization energies (IEs) are lower than those of the alkali metal atoms. Theoretical calculation has demonstrated that this kind of cluster represents a potential 'building block' for cluster-assembly materials with unique structural, electronic, optical, magnetic, and thermodynamic properties. To date, however, there have been no experimental results on the IEs of KnF (n gt 2) clusters. METHOD KnF (n?=?26) clusters were produced by the evaporation of a solid potassium fluoride salt using a modified thermal ionization source of modified design, and mass selected by a magnetic sector mass spectrometer where their IEs were determined. RESULTS Clusters KnF (n?=?36) were detected for the first time. The order of the ion intensities was K2F+ gt ? gt ?K4F+ gt ? gt ?K3F+K6F+? gt ?K5F+. The determined IEs were 3.99 +/- 0.20?eV for K2F, 4.16 +/- 0.20?eV for K3F, 4.27 +/- 0.20?eV for K4F, 4.22 +/- 0.20?eV for K5F, and 4.31 +/- 0.20?eV for K6F. The IEs of KnF increase slightly with the increase in potassium atom number from 2 to 6. We also observed that the presence of a fluorine atom leads to increasing ionization energy of bare metal potassium clusters. CONCLUSIONS The modified thermal ionization source provides an efficient way of obtaining the fluorine-doped potassium clusters. These results also present experimental proof that KnF (n?=?26) clusters belong to the group of 'superalkali' species.

RATIONALE: Theoretical calculations have shown that the first ionization energy of clusters of the type LinCl (n GT = 2), with more than eight valent electrons, is lower than that of alkali metal atoms; hence they are named superalkali. Superalkali clusters can mimic the chemical behavior of alkali metals and may be used as building blocks of new cluster-assembled materials. There is currently no reliable experimental proof of this kind of clusters and such proof is required. METHODS: The LinCl (n = 2-6) clusters were produced by a thermal ionization source of modified design, and mass selected by a magnetic-sector mass spectrometer. The modification pertains to the replacement of the side filaments by a cylinder in the triple-filament thermal ionization source. The sample, which is LiCl salt, was pressed into a ring and placed on the inner wall of the cylinder. RESULTS: It was observed that the ions of clusters with an even number of lithium atoms (Li2Cl+, Li4Cl+, Li6Cl+) are more stable than the odd-numbered ones (Li5Cl+, Li3Cl+). The ionization energies were determined to be 3.98 +/- 0.25 eV for Li2Cl, 4.10 +/- 0.25 eV for Li3Cl, 3.90 +/- 0.25 eV for Li4Cl, 4.01 +/- 0.25 eV for Li5Cl, and 4.09 +/- 0.25 eV for Li6Cl. The presence of a halogen atom reduces the ionization energy of the metal clusters. CONCLUSIONS: The thermal ionization source of modified design presents a suitable simple way to obtaining and measuring the ionization energies of very small lithium monochloride clusters. Clusters LinCl, n = 4 to 6, were detected for the first time. Copyright (C) 2012 John Wiley and Sons, Ltd.

The electronic structure and properties of dipotassiummonohalides are important for understanding the unique physical and chemical behavior of MnX systems. In the present study, K2X (here X=F, Cl, Br, I) clusters were generated in the vapor over salts of the corresponding potassium halide, using a magnetic sector thermal ionization mass spectrometer. The ionization energies obtained for K2F, K2Cl, K2Br, and K2I molecules were 3.82 +/- 0.1eV, 3.68 +/- 0.1eV, 3.95 +/- 0.1eV, and 3.92 +/- 0.1, respectively. These experimental values of ionization energies for K2X (X=F, Br, and I) are presented for the first time. The ionization energy of K2Cl determined by thermal ionization corresponds to previous results obtained by photoionization mass spectrometry, and it agrees with the theoretical ionization energy calculated by the ab initio method. The presently obtained results support previous theoretical predictions that the excess electron in dipotassiummonohalide clusters is delocalized over two potassium atoms, which is characteristic for F-center clusters.

Molecules of LinX (n = 2,3; X = Cl, Br, I) were examined with a magnetic sector mass spectrometer by surface ionization using a triple rhenium filament impregnated with fullerene (C-60). The ionization energies obtained for Li2Cl, Li2Br and Li2I Molecules are 3.8 +/- 0.1, 3.9 +/- 0.1 and 4.0 +/- 0.1 eV. respectively. The first ionization energy of Li2Cl is documented, while there are no literature data for the ionization energies of Li2Br and Li2I. The molecules of Li3Cl, Li3Br and Li3I were detected experimentally for the first time with ionization energies of 4.0 +/- 0.1, 4.1 +/- 0.1 and 4.1 +/- 0.1 eV, respectively. The ionization energies of LinX (n = 2, 3; X = Cl, Br, I) are in correlation with the theoretical prediction of their hyperlithiated configurations. Copyright (c) 2006 John Wiley and Sons, Ltd.

Ionization energies of hypervalent Li2F, Li2Cl and Na2Cl molecules detected by surface ionization electron impact neutralization mass spectrometry are reported. The ionization energies were 3.78 +/- 0.2 eV for Li2F, 4.93 +/- 0.2 eV for Li2Cl, and 4.21 +/- 0.2 eV for Na2Cl. The ionization energies (IE) agree with theoretical ionization energies calculated by ab initio methods,(1) supporting the theoretical prediction that Li2F has a hyperlithiated configuration in which the odd electron delocalizes over the two lithiums and with photoionization measurement.(2) The first ionization energy of Na2Cl was experimentally confirmed earlier(3-7) and for Li2Cl as well.(8) We have developed and used this new approach for the problem-in the present work ions were first formed by surface ionization, followed by electron attachment (neutralization).

The ionization and fragmentation of SF6 under electron impact has been examined by means of a trochoidal electron velocity selector and a mass spectrometer. The ionization efficiency curves of the positive ions were recorded and the appearance energies of different electronic states of these ions were determined. The experimental results were combined with auxiliary thermochemical data to evaluate the dissociation energies D circle degrees(F5S-F) = 4.01 eV, D degrees circle(F4S-2F) = 6.39 eV, D degrees circle(F3S-3F) = 9.98 eV, the ionization energy of SF5, = 11.27 eV and heats of formation Delta H degrees(f)(SF5+) = 1.81 eV, Delta H degrees(f)(SF4+) = 4.12 eV, Delta H degrees(f)(SF3+) = 4.11 eV and Delta H degrees(f)(SF3) = - 5.13 eV. (C) 1998 John Wiley and Sons, Ltd.

The formation of SF+, SF2+, SO+ and SO2+ fragment ions from dissociative ionization of the SO2F2 molecule has been studied by means of a trochoidal electron velocity selector coupled to a mass spectrometer. The ionization efficiency curves of ions were measured and their appearance energies, both in ground and excited states, were determined, The experimental findings were combined with available thermochemical data to determine the following values: ionization energy IE (SF2) = 10.08 eV; Heat of formation, Delta H-f(SF2+) = 7.01 eV and bond dissociation energy, D(F2S-20) = 9.94 eV. (C) 1997 by John Wiley and Sons, Ltd.

The temperature-programmed desorption (TPD) method combined with mass spectrometric analysis has been applied to the characterization of glassy carbon (GC) and modified glassy carbon surfaces. Five different samples of GC were obtained from a commercial resol type of phenol formaldehyde resin that bad undergone several treatments: the samples were either pure GC, GC treated with boron and phosphorus, or GC modified by metal (silver and palladium). Mass spectrometric analysis has shown that the thermal decomposition of surface oxide species results in desorption of H2O, CO and CO2, these being the major gas products. On the basis of the TPD spectra obtained, desorption energies have been calculated using a peak position method. The influence of CO2 oxidation on the surface properties of the samples was also investigated. It was concluded that metal deposition on a glassy carbon surface contributes to increased stability of surface oxide species, the most stable surface being one that has been modified by palladium deposition.

The dissociative ionization of sulphuryl fluoride (SO2F2) under electron impact has been examined by using a trochoidal electron velocity selector and a magnetic sector mass spectrometer. The ionization efficiency curves of SO2F2+, SOF2+, SO2F+ and SOF+ have been recorded and the appearance energies of different electronic states of these ions were determined. The results were used to evaluate the dissociation energy D(OSF2-O)=5.32 eV, enthalpies of formation Delta H-f(SO2F)=-427.5 kJ/mol (-4.43eV), Delta H-f(SO2F+)=616 kJ/mol (6.39 eV), Delta H-f(SOF)=-207.5 kJ/mol (-2.15 eV), Delta H-f(SOF+)=710 kJ/mol (7.36 eV) and the ionization energies IE(SO2F)=10.82 eV and IE(SOF)=9.51 eV.

The temperature-programmed desorption (TPD) method combined with mass spectrometric analysis has been applied to the characterization of glassy carbon (GC) and modified glassy carbon surfaces. Five different samples of GC were obtained from a commercial resol type of phenol formaldehyde resin that bad undergone several treatments: the samples were either pure GC, GC treated with boron and phosphorus, or GC modified by metal (silver and palladium). Mass spectrometric analysis has shown that the thermal decomposition of surface oxide species results in desorption of H2O, CO and CO2, these being the major gas products. On the basis of the TPD spectra obtained, desorption energies have been calculated using a peak position method. The influence of CO2 oxidation on the surface properties of the samples was also investigated. It was concluded that metal deposition on a glassy carbon surface contributes to increased stability of surface oxide species, the most stable surface being one that has been modified by palladium deposition.

The surface ionization method offers the possibility of measuring ionization energies of atoms, inorganic and organic molecules and clusters, In this study we report the results of the surface ionization of Li2F molecules on a rhenium surface, This work is an attempt to investigate the applicability of the surface ionization technique for the measurment of the ionization energies of hypervalent molelcules at high temperature, There are currently no reliable experimental data for the ionization energy of the Li2F molecule, This molecule has been chosen because previous theoretical calculations have shown that Li2F is a hypervalent (hyperlithiated) molecule with a low ionization energy, The ionization energy was determined to be 5.42+/-0.04 eV.