Summary In order to study the influence of the ion bombardment parameters on the achievable depth resolution of AES sputter depth profiles, 500 Å thick Ta2O5-layers produced by anodic oxidation of polished polycrystalline Ta-substrates were sputter depth profiled with Ar+- and Xe+-ions in a Scanning Auger Microprobe. The 90%–10% interface widthsz were measured for bombarding ion energies from 0.5 to 5 keV and angles of incidence of 15°, 33° and 56°, respectively.z reduces from 48 Å for Ar+-bombardment at = 15° andE = 5 keV to 20 Å when bombarding at = 56° andE = 1 keV. The corresponding values for Xe+-bombardment are 31 Å and 18 Å. The influence of the ion bombarding energy and angle on the interface broadening is discussed by means of a simple model. From corresponding evaluations the maximum transportation length of layer species into the substrate is found to be proportional toE0.5.
Zum Einfluß der Ionenbeschußparameter auf die Tiefenauflösung bei der AES-Sputtertiefenprofil-analyse von Ta2O5/Ta mit Ar+ und Xe+
SIMS studies of glasses indicate that calibration of positive monatomic ion yields via relative sensitivity factors (RSF) is significantly dependent both on the kinetic energyEk and on the massMt of the analyzed ions. Due to elemental differences in the energy distributions of the sputtered ions, relative emissivities at highEk are radically different from those at the tops of the distributions. While the RSF values of cations from glasses range within ca. 3 powers of ten, atEk above ca. 40 eV the range remains within a factor of ten or less, and further change of relative elemental sensitivities withEk is slow. At low exit energy the LTE formalism is reasonably well obeyed. At highEk, a trend is noted towards a relative suppression of the ion yields of lowvalent elements.Measurements of isotope fractionation in secondary ion yield were performed on 17 elements sputtered from glasses. The mass factor (defined by the proportionality of the yield toMi–
) is found to range from near-zero to2.5, dependent on the element and onEk. For most elements a drops steeply at lowEk, but generally a slow rise is noted at higher energies. The behaviour of appears to be to some extent connected with the shape of the energy distribution curve. The dependence of onEk and on elemental parameters can qualitatively be described in terms of a simple phenomenological model. 相似文献
Zusammenfassung Das für Zweistoffsysteme angegebene Auswerteverfahren zur Ermittlung der freien Zusatzenthalpie GE und der chemischen Zusatzpotentiale
iE
aus massenspektrometrischen Daten wird auf Dreistoffsysteme erweitert.
Mass spectrometric determination of thermodynamic activities in ternary systems
A method for the evaluation of the excessGibbs free energy GE and the excess chemical potentials
iE
from mass spectrometric data, previously derived for binary systems, is applied to ternary systems.
The reaction of [RuCp(CH3CN)3]PF6 with 1 equiv of N-Me-imidazole results in the quantitative formation of [RuCp(1N-N-Me-imidazole)(CH3CN)2]PF6 (1) featuring a 1N rather than a 1C bound N-Me-imidazole ligand. According to DFT/B3LYP calculations, 1N coordination of N-Me-imidazole is preferred over 1C coordination by 25.5kJ/mol. Upon exposure to air 1 reacts with oxygen and water to afford the novel hydroxo-bridged dinuclear complex of [Ru2Cp2(1N-N-Me-imidazole)2(-OH)2](PF6)2 (2) featuring a metal-metal single bond. The dimeric nature of 2 was confirmed by a single-crystal X-ray structure analysis. 相似文献
Accurate density measurements over the whole composition range were made at a temperature of 298.15 K under ambient pressure for the mixtures of ethylene glycol monomethyl ether (2-methoxyethanol, C3H7O2; C1E1), or diethylene glycol monomethyl ether (2-(2-methoxyethoxy)ethanol, C5H12O3; C1E2), or triethylene glycol monomethyl ether [2-{2-(2-methoxyethoxy)ethoxy}ethanol, C7H16O4; C1E3) in aqueous salt solutions having a common anion with a view to examining the cationic effect on the volumetric properties. To gain insight into the mixing behavior, results of the density measurements were used to estimate excess molar volumes, VmE, apparent molar volumes, V, i, partial molar volumes,
, excess partial molar volumes, Vm,iE, and their limiting values at infinite dilution, V, i, Vm,i, and Vm,iE,, respectively. Aqueous solutions of the chlorides of lithium, sodium, potassium, and calcium in a concentration range to ca. 1 mol-kg–1 were chosen for investigation as this concentration is used most frequently in applied chemistry. All mixtures except that containing lithium chloride show a decrease in the magnitude of VmE with the addition of a salt when compared to salt-free mixtures. Comparison of the derived volumes at infinite dilution suggested modification of the water structure as well as an electrostatic interaction between the ionic species and an alkoxyethanol molecule. 相似文献
Measurements are reported on the formation of negative ions in O2, O2/Ar and O2/Ne clusters aimed at establishing the mechanisms of anion formation and the role of inelastic electron scattering by the cluster constituents on negative ion formation in clusters. In the case of pure O2 clusters the main anions we detected are of two types: O–(O2)n0 and (O2)
n1–
. The yields of O–(O2)n showed maxima at 6.3, 8.0 and 14.0 eV and the data suggest O– as their precursor; the maxima at 8 and 14 eV are due to the production of O– via symmetry forbidden dissociative attachment processes in O2 at these energies which become allowed in clusters. The yields of (O2)
n–
showed a strong maximum at near-zero energy (0.5 eV) and also at 6.3, 8 and 14 eV. With the exception of the near-zero energy resonance, the (O2)
n–
anions at 6.3, 8 and 14 eV are attributed to nondissociative attachment of near-zero energy secondary electrons to O2 clusters. The slow secondary electrons result predominantly from scattering via the O
2–
negative ion states of incident electrons with energies in their respective regions. Similar results were obtained for the mixed O2/rare gas clusters except that now a feeble and distinctly structured contribution in the yields of O–(O2)n, (O2)
n–
(and Ar(O2)
n–
) was observed at energies >10 eV. These anions are believed to have the lowest negative ion states of Ar*– (Ne*–) as their precursors. 相似文献
Summary The reaction of (C8H8)YCl(THF) with NaC5H4CH3 in tetrahydrofuran leads to (C8H8)Y(C5H4CH3)(THF). The X-ray structural analysis shows the compound to be orthorhombic witha=1157.5 (2),b=1553.2 (5),c=1718.9 (6) pm, space group Pbca,Z=8, andD (calcd)=1.48 g/cm–3. The structure was solved from 1643 observed reflections withFo4 (Fo) and refined to a finalR factor of 0.058. The expected sandwich structure is bent according to the ring centroid-Y-ring centroid angle of 149° caused by theTHF molecule coordinated to Y.
Herrn Prof. Dr. E. Hengge mit den besten Wünschen zum 60. Geburtstag gewidmet. 相似文献
The valence threshold photoelectron spectrum of NF3 is reported for the first time in the literature, and threshold photoelectron–photoion coincidence (TPEPICO) spectroscopy has measured, state-selectively, the decay dynamics of the valence states of NF3+ in the range 13–23 eV. Vacuum–UV radiation from the Daresbury synchrotron source dispersed by a 1 m Seya-Namioka monochromator photoionises the parent molecules. Electrons and ions are detected by threshold electron analysis and time-of-flight mass spectrometry, respectively. TPEPICO spectra are recorded continuously as a function of photon energy, allowing coincidence ion yields of the fragment ions and the breakdown diagram to be obtained. A comparison of the integrated threshold photoelectron and the total ion signals as a function of energy suggests that, in the range 16–19 eV, autoionisation via Rydberg states of NF3 makes a significant contribution to the production of threshold electrons. The 50% crossover energy for production of NF2+ from NF3+ is determined to be 14.10±0.05 eV. The first onsets for NF2+ and NF+ production are 13.95±0.05 and 17.6±0.1 eV, respectively. The majority of the Franck–Condon region of the
ground state of NF3+ is stable with respect to dissociation to NF2+, whereas the unresolved
states and most of the
state dissociate exclusively to NF2+. The
and
states dissociate to NF+. Translational kinetic energy releases have been measured in NF2+ and NF+ at the energies of the Franck–Condon maxima of the valence states of NF3+. The results are compared with models assuming statistical and impulsive dissociation. The Ã/
states of NF3+ dissociate directly from the excited-state potential energy surface to NF2+, whereas the higher-lying
state probably dissociates off the ground-state surface following rapid internal conversion. It is not possible to correlate unambiguously the formation of NF+ with either F2 or 2F, although on energetic grounds the latter products are more likely. Assuming that the neutral products are 2F, no information is obtained whether the two N–F bonds break simultaneously or sequentially. 相似文献
Ions of gold monomer and clusters emitted from a liquid metal ion source were mass-selected, and deposited on cleaved HOPG (highly oriented pyrolytic graphite) surfaces and on amorphous carbon thin films at room temperature with the impinging energy Ei from 0 to 500 eV. The coverage of deposited ions were 1/100 and 1/1000 monolayers on HOPG surfaces and 1/3 monolayers on carbon films. Scanning tunneling microscopy of the HOPG surfaces deposited with low impinging energy (Ei<50 eV) revealed that large clusters with diameters ranging from 2 to 5 nm and height of 1–2 layers were present instead of isolated monomers and original clusters. When Ei was higher than 100 eV, HOPG surfaces were damaged and only bumpy surfaces were observed by STM. Transmission electron microscopy of Au+-deposited carbon films showed the formation of clusters with diameter 0.5–20 nm, depending on the Ei and the time elapsed after deposition. 相似文献
The mass spectra of a series of thirteen m- and p-substituted benzils have been determined at several ionising voltages below 20 eV and at 70 eV. At ionising voltages up to 5 eV above the ionisation potentials the benzil molecular ions decompose entirely by two pathways to give substituted and unsubstituted benzoyl ions. Fractional intensities of the molecular ion (FM), substituted (FX) and unsubstituted (FH) benzoyl ions were obtained for each benzil as a function of energy from measured ionisation efficiency curves, and ionisation and appearance potentials for all major ions determined from the ionisation efficiency curves by a semilogarithmic method. Various correlations of ion intensity and energy parameters with δ+ and δ constants are examined; these are generally poor. Fair correlations are obtained between log (FX/FH) or (AP – AP) and δ or δ+, and these are interpreted in terms of the expected effect of substituents on the stabilities of the product ions in the decompositions. A good correlation is observed between log (FX/FH) and AP · AP; this suggests that substituents affect FX/FH mainly by changing the activation energies for the competing decompositions of the molecular ions. The competitive shift has a marked effect on these appearance potentials so that in this system AP – IP is not a good measure of the activation energy for the primary decompositions. 相似文献
The mass spectra of the following compounds have been studied: and the fragmentation pathways established with the aid of accurate mass measurements, metastable transition and appearance potential determination. The mass spectra show that the sulphur-containing compounds (II to IV) give a stronger molecular ion that that of compound I. A further significant difference is the low intensity, in the mass spectra of II to IV, of the fragments relative to the processes that occur in I, probably because the electron removed upon ionisation belongs to the sulpher atom in compounds II to IV and to the oxygen in compound I. The isomeric compounds, (III and IV) show quite different mass spectra, The radicals containing only Phosphorus and oxygen have an ionisation potential close to 9 eV and the presence of sulphur considerably lowes this value. The measured ionisation potentials of compounds I to IV are respectively, 10·70, 9·55, 9·20 and 9·00eV. The heats of formation of compounds II and III have been estimated as ?176 and ?118 Kcal mole?1, respectively. 相似文献
Excess chemical potentials and excess partial molar enthalpies of 1,2- and 1,3-propanediols (abbreviated as 12P and 13P), Ei, and HEi (i = 12P or 13P) were determined in the respective binary aqueous solutions at 25°C. For both systems, the values of Ei are almost zero, within ±0.4 kJ-mol–1. However, the excess partial molar enthalpies, HEi show a sharp mole fraction dependence in the water-rich region. Thus, the systems are highly nonideal, in spite of almost zero Ei. Namely, the enthalpy-entropy compensation is almost complete. From the slopes of the HEi against the respective mole fraction xi we obtain the enthalpic interaction functions between solutes, Hi–iE, (i = 12P or 13P). Using these quantities and comparing them with the equivalent quantities for binary aqueous solutions of 1-propanol (1P), 2-propanol (2P), glycerol (Gly), and dimethyl sulfoxide (DMSO), we conclude that there are three composition regions in each of which mixing schemes are qualitatively different. Mixing Schemes II and III, operative in the intermediate and the solute-rich regions, seem similar in all the binary aqueous solutions mentioned above. Mixing Scheme I in the water-rich region is different from solute to solute. 12P shows a behavior similar to that of DMSO, which is somewhat different from typical hydrophobic solute, 1P or 2P. 13P, on the other hand, is less hydrophobic than 12P, and shows a behavior closer to glycerol, which shows hydrophilic behavior. 相似文献
The electronic and geometric structures and the dissociation energies of the isolated molecule of heme dimer (heme)2 = (FeC34H32O4N4)2 and its ion (heme)
2+
= (FeC34H32O4N4)
2+
in the states with different multiplicities have been calculated by the density functional theory B3LYP method with the Gen-1
= 6-31G*(Fe) + 6-31G(C,H,N,O) and Gen-2 = 6-311++G*(Fe) + 6-31G*(C,H,N,O) basis sets. The computation results are compared
with the analogous calculated data on monomeric heme and hemin+, as well as the previously considered dimeric ferriporphyrin X molecule and ion FeC34H31O4N4)
20, +
. In the heme dimer cation (heme)
2+
, which is identified in mass spectra, the rings are linked with each other by a pair of Fe carbonyl bridges Fe⋯Ob = C(OH) and a pair of hydrogen bridges OHb⋯N. According to the calculations, the most favorable state for (heme)
2+
is the sextet in which five unpaired electrons are approximately uniformly distributed over the metal atoms, whereas the
states with higher multiplicities 8 and 10 are, respectively, 0.15 and 0.20 eV higher on the energy scale. For the neutral
dimer (heme)2, the quintet is favorable in which each of the two Fe atoms has two unpaired electrons, and the states with the higher multiplicities
7 and 9 are only 0.10–0.15 eV higher. The calculated energies of dissociation D of the dimers into monomers point to a rather high stability of the (heme)
2+
(D ∼ 1.4 1.4eV) and to a low stability of the neutral dimer (heme)2 (D ∼ 0.3 eV). The R(Fe⋯Ob) distances in the bridges in (heme)
2+
are 0.2–0.4 ? shorter than in (heme)2. The trends in the behavior of the energetic and structural characteristics of the dimers (R(Fe-N), displacements of Fe atoms from the porphyrin ring plane, character of ring distortions, etc.) associated with the
involvement of the
and
AOs of Fe atoms in bonding, as well as the spin density distribution over the Fe atoms and the rings, are analyzed as a function
of the multiplicity and charge of the system. Differences in the character of interaction of the heme and ferriporphyrin dimers
with molecular oxygen are discussed.
Original Russian Text ? O.P. Charkin, N.M. Klimenko, D.O. Charkin, S.H. Lin, 2007, published in Zhurnal Neorganicheskoi Khimii,
2007, Vol. 52, No. 7, pp. 1166–1174. 相似文献
The reaction of primary amines RNH2 (R: Me, Et, iPr, tBu and Ph) with 1,2-dibromoethane gave N,N′-disubstituted ethylenediamines R-NH-CH2CH2-NH-R (1) in yields ranging from 10% (1a; R=Me) to 70% (1d, R=tBu; 1e, R=Ph). Piperazines and N-substituted polyethyleneimines were identified (1H NMR, 13C NMR and EI-MS) as side products of the reaction and isolated by fractional distillation. The piperazines 2 are formed in yields of 3-10% and can be separated from the diamines 1 in all cases, except for R=Me and Ph. The polyamine homologues RNH-[CH2CH2NR]n-H (3-5) were isolated in yields ranging from 0.1% (n=4, R=iPr) to 14% (n=2, R=iPr). The yields of 1 increase with the size of the substituent R, no obvious trend exists for the yields of the side products. 相似文献
The P-type delayed fluorescence (DF) Si→So of aromatic compounds results from the population of excited singlet states Si by triplet—triplet annihillation (TTA) of molecules in their lowest and metastable triplet state T1 : T1 + T1 Si + So; Si may be any excited singlet state whose excitation energy E(Si ? 2 E(T1). TTA of unlike molecules A and B (hetero-TTA) may lead to excited singlet states either of A or of B. In particular, if E(TA1) < E(T1B), hetero-TTA may lead to excited singlet states SkA which are not accessible by TTA of 2 T1A. In the present paper we report the first example of the detection of the DF from a very short-lived upper excited singlet state SkA which has been populated by hetero-TTA. The systems investigated are liquid solutions of A = anthracene-h10 or anthracene-d10 or 9,10-dimethylanthracene and B = xanthone in 1,1,2-trichlorotrifluoroethane at 243 K. SkA is the lowest 1B3U+ state (Bb state) of anthracene. 相似文献
Summary The two title compounds12b and13b have been prepared by direct oxidation of the corresponding 10-oxo-19-norcolcalciferol derivatives3c and4c withMCPBA. The generation of12b and13b by treatment of the 7 epoxidized ethylisoxazolin adducts of 5Z- and 5E-cholecalciferol8a,8b and9a,9b with Mo(CO)6 failed, since besides the retroaldol cleavage of the heterocycle a deoxygenation of the oxirane with retention of configuration to the 7 double bond occurs. 相似文献
Summary Half-wave potentials for a one-electron reduction of copper(II) complexes containing polydentate ligands can be calculated using the equationE1/2=E0(Cu2+/+)+ijEi where Ei are contributions related to the electronic and steric properties of the ligands. The values of 18 Ei contributions are presented and explained, and the effect of the solvents on the half-wave potentials is exemplified.Dedicated to Prof. Dr. Viktor Gutmann to his 70th birthday 相似文献
The fragmentation behaviour of size selected neutral (D2O)n clusters withn4 after ionization with 70 eV electrons is subject of this work. Size selection by scattering the cluster beam from a He target beam in combination with a quadrupole mass filter and time resolved measurements at specific laboratory angles enables us to determine the neutral precursor masses of the detected ions. The measured fragment pattern is dominated by deuterated ions of the form (D2O)n–xD+ withx1. The dimer fragmentation which leads with a probability of 62.5% to the D3O+ ion and with 37.5% to D2O+ can be explained by fast intracluster ion-molecule reactions of charged monomer fragments reacting with the partner molecule. For larger clusters the fragmentation process can be rationalised by the creation of an initially highly excited D3O+ (D2O)x complex which is stabilized by evaporating additional monomer units with the main fragment channel (D2O)D+ forn=3 and (D2O)2D+ forn=4. With increasing cluster size an increasing tendency of evaporation of more than one water monomer unit has been observed. 相似文献
Deaerated 5 M NaCl solution is irradiated in the presence of UO2 pellets with α-radiation from238Pu. Experiments are conducted with238Pu doped pellets and others with238Pu dissolved in the brine. The radiolysis products and yields of mobilized U and Pu from the oxidative dissolution of UO2 are determined. Results found for radiolysis products and for the oxidation/dissolution of pellets immersed in Pu containing
brine are similar to results for Pu doped pellets, where the radiation chemical processes occur only in the liquid layer of
some 10 σm thickness adjacent to the pellet. The yield of radiolysis products is comparable to earlier results, that of mobilized
U from the pellets is < 1% of the total amount of oxidized species. Thus, the radiation chemical yield (G-value) for mobilized hexavalent U is < 0.01 ions/100 eV. In spite of the low radiation yield for the corrosion, the rate
of UO2dissolution is higher than expected for the concentrations of long-lived oxidizing radiolysis compounds found in the solutions. 相似文献
Cp2ZrCl2-catalyzed (Cp = 5-C5H5) hydroalumination of substituted norbornenes withi-Bu2AlCl was conducted, yielding higher cycloalkylhaloalanes with high yields.Institute of Organic Chemistry, Ural Branch, Russian Academy of Sciences, 450054 Ufa. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2791–2798, December, 1992. 相似文献