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1.
Threshold energies (6.1 <Et ? 8.6 eV) are determined for photoelectron emission by 16 inorganic cations in aqueous solution Et values are correlated with gas-phase ionization potentials, solvation and reorganization free energies, standard reduction potentials and ligand field stabilization energies (five transition metals). Dielectric saturation is shown to drastically lower threshold energies. 相似文献
2.
Threshold energies Et are determined for photoelectron emission by 20 inorganic anions in aqueous solution (7.1 < Et < 9.1 eV). Calculated values of Et for Cl?, Br?, I? agree with experiment. The Et are correlated with charge-transf absorption spectra. 相似文献
3.
P.A.G. OHare H.E. Flotow E.H. Appelman 《The Journal of chemical thermodynamics》1982,14(12):1191-1196
The low-temperature (5 to 310 K) heat capacity of cesium fluoroxysulfate, CsSO4F, has been measured by adiabatic calorimetry. At T = 298.15 K, the heat capacity Cpo(T) and standard entropy So(T) are (163.46±0.82) and (201.89±1.01) J · K?1 · mol?1, respectively. Based on an earlier measurement of the standard enthalpy of formation ΔHfo the Gibbs energy of formation ΔGfo(CsSO4F, c, 298.15 K) is calculated to be ?(877.6±1.6) kJ · mol?1. For the half-reaction: SO4F?(aq)+2H+(aq)+2e? = HSO4?(aq)+HF(aq), the standard electrode potential E at 298.15 K, is (2.47±0.01) V. 相似文献
4.
The Measurement of the Gibbs Energy of Transfer Between Oil and Water Using a Nano‐Carbon Paste Electrode
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The use of nano‐carbon paste electrodes for the measurement of Gibbs energies of transfer between oil and aqueous phases is reported. In this method the oil of interest is used as the binder for the nano‐carbon paste electrodes and the molecule of interest is dissolved in the organic or aqueous phase. Voltammetry is performed over a period of time and used to monitor the transfer of the molecule between the two phases. The method is illustrated for the transfer of ferrocenemethanol between water and oil using the ferrocenemethanol / ferroceniummethanol (FcCH2OH/FcCH2OH+) redox couple. Three pairs of voltammetric peaks were observed in a 0.1 M KCl solution when the nano‐carbon paste electrode was modified by dissolution of FcCH2OH in the binder oil: P1 [E=0.23 V, 0.17 V vs. Ag/AgCl (1 M KCl)], P2 [E=0.36 V, 0.32 V vs. Ag/AgCl (1 M KCl)] and P3 [E=0.55 V, 0.46 V vs. Ag/AgCl (1 M KCl)]. These are assigned to the FcCH2OH species existing in the aqueous solution [FcCH2OH(aq)/FcCH2OH+(aq)], originating in the oil (o) [FcCH2OH(o)/FcCH2OH+(aq)] and to oxidation of adsorbed (ads) material on the nano‐carbon [FcCH2OH(ads)] respectively. When supporting electrolyte containing the anions Cl?, NO3? or SCN? was used, an expulsion of the oxidised ferrocene occurred and the difference in midpoint potentials (Emid) between the peaks P1 and P2 observed in these experiments allowed the calculation of the Gibbs energy (ΔG°) of transfer of ferrocenemethanol from water to oil. The average ΔG° value thus obtained was (?12.7±0.2) kJ mol?1. For more hydrophobic anions (X?=PF6?, AsF6?), the electron transfer is coupled to the transfer of the anion into the oil and the ΔG° for the transfer of the ion pair of FcCH2OH+ and X? ions from water to oil was found to be ?1.3 and ?3.9 kJ mol?1 for PF6? and AsF6? respectively. 相似文献
5.
Cubic and trigonal (NH4)2SiF6 have low-temperature dielectric-loss maxima with activation energies Ea (cubic) = 5.4 kcal/mol and Ea(trig.) = 8.7 kcal/mol, not related to ionic reorientation and probably caused by OH? impurities. 相似文献
6.
Calorimetric measurements of the enthalpy of reaction of WO3(c) with excess OH?(aq) have been made at 85°C. Similar measurements have been made with MoO3(c) at both 85 and 25°C, to permit estimation of ΔH°=?13.4 kcal mol?1 for the reaction WO3(c)+2OH?(aq)=WO2?4(aq)+H2O(liq) at 25°C. Combination of this ΔH° with ΔH°f for WO3(c) leads to ΔH°f=?256.5 kcal mol?1 for WO2?4(aq). We also obtain ΔH°f=?269.5 kcal mol?1 for H2WO4(c). Both of these values are discussed in relation to several earlier investigations. 相似文献
7.
The formation of negative ions in electron transfer reactions between hyperthermal alkali atoms (Na, K) and WF6 has been studied in the energy range 0–30 eV c.m. Relative cross sections and translational energy thresholds for ion pair formation have been measured, from which the following electron affinities (EA) and bond dissociation energies (D) have been derived: EA(WF6) = 3.7 eV, EA(WF5) = 1.25 eV, D(WF5—F) = 5.1 eV, D)WF5—F?) = 5.4 eV, D(WF?5—F) = 7.6 eV. Several ion molecule reactions are discussed which result in formation of secondary fragmentation ions and WF?7. 相似文献
8.
In this paper we report the results of an experimental study of the vacuum ultraviolet absorption spectra of molecular impurity states of methyl iodide in Ar (density range ? = 0–1.4 g cm?3) and in Kr (? = 0–2.3 g cm?3), of carbon disulphide in Ar (? = 0–1.4 g cm?3) and of formaldehyde in Ar (? = 0–1.25 g cm?3). The experimental results provide new information regarding medium perturbations of intravalenc transitions, of the lowest extravalence transitions and of transitions to mixed valence—Rydberg configurations, which serve as a diagnostic tool to distinguish between different types of electronic excitations. All the lowest extravalence molecular excitations exhibit appreciable blue spectral shifts at moderate and at high fluid densities, intravalence transitions are practically insensitive to medium effects, while excitations to mixed valence—Rydberg configurations are characterized by a moderate blue spectral shift. New information has been obtained concerning the energetics of molecular ionization processes in a dense fluid. The high n = 2–5 Rydberg states of CH3l exhibit a large red shift at moderate (? = 0–0.5 cm?3) Ar densities. The ionization potential Eg and the effective Rydberg constant G for CH3I in Ar was found to decrease from G = 13.6 eV and Eg = 9.55 eV at ? = 0 and Eg = 9.08 eV and constant G for CH3l in Ar was found to decrease from G = 13.6 eV and Eg = 9.55eV at ? = 0 and Eg = 9.08 eV and G ≈ 7.15 eV at ? = 0.5 g cm?3. Experimental evidence was obtained for the identification of n = 2 molecular Wannier impurity states of CH3I and of CH2O in liquid Ar. These spectroscopic data result in Eg ≈ 8.6 eV for CH3I in liquid Ar and Eg ≈ 10.2 eV for CH2O in liquid Ar. 相似文献
9.
C.B. Cosmovici E. DAnna A. DInnocenzo G. Leggieri A. Perrone R. Dirscherl 《Chemical physics letters》1977,47(2):241-244
Dissociation energy (Do = 4.29 ± 0.05 eV), threshold energy (E = 0.83 ± 0.05 eV) and forward scattering at a collision-al energy Ec = 1.1 cV have been found by crossing beam of Yb atoms with a supersonic seeded beam of He + O2 at collisional energies up to Ec = 1.4 eV. 相似文献
10.
Using the laser photoemission technique, a comparative study of thermodynamic and energy characteristics of electron transfer (ET) is carried out for a number of alkylaryl intermediates (IM) (benzyl, benzhydryl radicals) and alkyl halides (chloromethyl and dichloromethyl radicals). It is found that the standard free energies of activation of radicals under study are 0.34–0.38 eV and the preexpoential factors are between 109 and 1010s?1 and weakly depend on the solution nature. The reorganization energies of the medium for these IM are estimated in terms of the classical Marcus theory. The results are compared with the literature data on the dissociative ET in monohalogenomethanes CH3Hal/CH3Hal?·, polychloromethanes CHnHal4 ? n /CHnHal 4?n ?· , and some other systems. Possible reasons for the different probabilities of observing reversible ET for IM under study are discussed. 相似文献
11.
Classical trajectory calculations are used to compute the formation cross section (suitably defined) for strongly interacting collision complexes formed in H+ + D2 collisions in the kinetic energy range from 0.1 to 4 eV. This cross section corresponds to the usual Langevin cross section only if the kinetic energy is less than 0.2 eV, and provided that little initial excitation is present, while for higher kinetic energies it drops exponentially. It is in much better agreement with absolute integral cross sections observed experimentally than the latter. Further study shows that it is the contribution from large orbital anglular momenta, which the Langevin cross section overestimates. Orbiting complexes (of H+ around D2) play a negligible role, and are very short-lived. The lifetime of strongly coupled complexes is estimated to be 450 E?1.3 fs, where E is the total energy in eV. The use of trajectory data to improve Light's phase space theory is discussed. 相似文献
12.
The aqueous chemistry of phosphorus is dominated by P(V), which under typical environmental conditions (and depending on pH and concentration) can be present as the orthophosphate species H3PO 4 0 (aq),H2PO 4 ? (aq),HPO 4 2? (aq) or PO 4 3? (aq). Many divalent, trivalent and tetravalent metal ions form sparingly soluble orthophosphate phases that, depending on the solution pH and concentrations of phosphate and metal ions, can be solubility limiting phases. Geochemical and chemical engineering modeling of solubilities and speciation require comprehensive thermodynamic databases that include the standard thermodynamic properties for the aqueous species and solid compounds. The most widely used sources for standard thermodynamic properties are the NBS (now NIST) Tables (from 1982 and earlier, with a 1989 erratum) and the final CODATA evaluation (1989). However, a comparison of the reported enthalpies of formation and Gibbs energies of formation for key phosphate compounds and aqueous species, especially H2PO 4 ? (aq) and HPO 4 2? (aq), shows a systematic and nearly constant difference of 6.3 to 6.9 kJ?mol?1 per phosphorus atom between these two evaluations. The existing literature contains numerous studies (including major data summaries) that are based on one or the other of these evaluations. In this report we examine and identify the origin of this difference and conclude that the CODATA evaluation is more reliable. Values of the standard entropies of the H2PO 4 ? (aq) and HPO 4 2? (aq) ions at 298.15 K and p?° =1 bar were re-examined in the light of more recent information and data not considered in the CODATA review, and a slightly different value of S m o (H2PO 4 ? , aq, 298.15 K) = (90.6±1.5) J?K?1?mol?1 was obtained. 相似文献
13.
Harold F. Winters 《Chemical physics》1979,36(3):353-364
The absolute total dissociation cross section for ethane is reported for electron energies between 10 and 600 eV. A maximum value of 7.6 × 10?16 cm2 occurs at 80 eV while the apparent threshold is ≈ 10 eV. Dissociative ionization is more probable than dissociation into neutral fragments at all energies except in the threshold region. The data indicates that fragmentation involving methane elimination (c? + C2 H6 → e? + CH4 + CH2) occurs in less than 2% of the dissociative events for 50 < E < 600 eV. Arguments are presented which suggest that some of the lower excited states of ethane are stable against dissociation. 相似文献
14.
《Chemical physics letters》1986,125(2):97-100
Relative partial photoionization cross sections as a function of photon energy, over the range 20–110 eV, have been measured for the valence bands of Cr(CO)6, Mo(CO)6 and W(CO)6. All three t2g−1 bands show a very pronounced increase in intensity at photon energies (hv) corresponding to np resonant absorption (Cr(CO)6, hv = 52.5 eV, n = 3; Mo(CO)6,hv = 48 eV, n = 4; W(CO)6, hv = 44 and 53 eV, n = 5). The other valence bands show a small intensity increase at similar energies. Observation of such resonant photoemission provides an unambiguous method for assignment of nd bands in the photoelectron spectra of gas-phase molecules. 相似文献
15.
H. Brenten H. Müller V. Kempter 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,21(1):11-18
We have investigated K+ collisions (200 to 1000 eV) under grazing incidence with partially alkalated (K, Cs) W(110) surfaces by energy analysis of the ejected electrons. Three different mechanisms for electron emission could be identified (1) Kinetic emission mainly confined to projectile energies greater than 300 eV, (2) Auger deexcitation of excited projectile valence states yielding electrons with energies up to about 2.9 eV and (3) Creation of inner shell vacancies (Cs(5p ?1) and K(3p ?1)) which gives rise to Auger type processes (OVV and MVV) and to the formation of autoionizing states of the type A (np 5 n′s n″l) (A=Alkali atom). The relative importance of the three mechanisms is studied as a function of the alkali coverage of the surface and of the projectile's energy. 相似文献
16.
R.P. Tomlins 《The Journal of chemical thermodynamics》1976,8(12):1195-1197
The excess Gibbs free energies GE for tetra(2-ethylbutoxy)silane (tkebs) + cyclohexane, + benzene, and + carbon tetrachloride have been measured at 308.15 K with a new vapour-pressure apparatus. For tkebs + cyclohexane, GE is negative with a minimum value of ?538 J mol?1 near x2(tkebs) = 0.39. For tkebs + benzene, the minimum value of GE is ?453 J mol?1 near x2 = 0.41, and for tkebs + carbon tetrachloride, GE has a minimum value of ?715 J mol?1 near x2 = 0.39. 相似文献
17.
Photoelectron energy distribution curves from solid CO2 have been determined for excitation energies from hv = 14 up to 40 eV using synchrotron radiation. A 1:1 correspondence to the gas-phase photoelectron spectrum is observed for the occupied molecular orbitals. The vertical binding energies EBv (EVAC = 0) and widths (fwhm) of the valence bands of solid CO2 are determined to be 13.0 and 0.95 eV (1πg); 16.7 and 1.1 eV (1πu); 17.6 and 0.85 eV (3σu) and 18.8 and 0.8 eV (4σg) for the individual bands respectively. The partial photoemission cross sections differ importantly from those of the gas phase in exhibiting pronounced maxima at 5.2 eV (1πg), 4.4–5.3 eV (1πu + 3σu) and 4.2 eV (4σg) above the vacuum level, which is attributed to effects of high density of final (conduction-band) states. Further weaker maxima are observed at higher photon energies. Contrary to the case for the gas phase, the resonances are unperturbed in the solid by degenerate autoionizing molecular Rydberg states. The molecular origin of the resonances in the continuum is discussed and related to X-ray absorption spectra, electron-scattering data and to theoretical cross-section calculations. It is shown that the same set of resonances is observed in the different experiments. The resonances occur however at different energies due to different Coulomb interactions. The photoemission results presented provide also a key to the hitherto unexplained optical spectrum of solid CO2 in the VUV range, making possible an assignment of the structures observed to Frenkel-type excitons (hv ≤ 15 eV) and interband transitions (hv ? 15 eV). 相似文献
18.
G. Ganteför M. Gausa K. H. Meiwes-Broer H. O. Lutz 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1989,12(1-4):405-409
Photoelectrons from mass-identified jet-cooled tin and lead cluster anions (Sn n ? , Pb n ? ) are detached by ultraviolet laser light (hν=3.68 eV). The photoelectron energy spectra give the detachment energies of ground state cluster anions (electron affinities) as well as excitation energies of neutral clusters in the geometry of the anions. The energy spectra for Sn n ? are dominated by flat thresholds with ann-dependence similar to that of other group IV clusters. In contrast, for Pb n ? we find pronounced narrow lines close to threshold, generally followed by a 0.3–1.4 eV gap which indicates closed-shell behaviour of Pb n ? for nearly alln. 相似文献
19.
The 1B2u1A1g fluorescence of benzene resulting from the impact of low energy electrons (0–30 eV) has been studied in the pressure range 10?4 ?2 × 10?3 torr. It is found that the apparent emission cross section near threshold varies linearly with the pressure. A reaction scheme explaining this behaviour is given. From the absolute value of the apparent emission cross section it follows that excitation of the 3E1u state is by far dominant over excitation of the 1B2u state at low electron impact energies. 相似文献
20.
Transmission electron spectroscopy has been applied to determine the energies of resonances in HF. In addition to a sharp resonance at 10.05 eV, a resonance series exhibiting both vibrational and rotational structure is resolved in the energy range between 12 eV and 13 eV and the following molecular constants are obtained: B = 20.4 cm?1, re, = 0.93 Å, ωe 0.132 eV, ωexe = 0.006 eV and De = 0.73 eV. The resonance spectrum is analysed with reference to an electron energy loss spectrum and approximate potential energy curves are deduced. Serious discrepancies are found between the present results and the data reported by Spence and Noguchi. 相似文献