Inner-shell excitation and EXAFS-type phenomena in the chloromethanes

Small angle inelastic scattering of 2.5 keV electrons was used to study the inner-shell excitation of CH₄, CH₃Cl, CH₂Cl₂, CHCl₃, CCl₄ and C₂H₅Cl in the regions of carbon 1s, chlorine 2p and chlorine 2s excitation. Structure observed below the carbon 1s ionization threshold in each molecule is assigned to promotions of a carbon 1s electron to unoccupied valence and Rydberg orbitals. Trends in the distribution of spectral intensities through the series of chloromethane carbon 1s spectra are discussed in terms of the growth of a potential barrier. Broad features are observed in the chlorine 2p continua of CH₂Cl₂, CHCl₃ and CCl₄ and the carbon 1s continuum of CCl₄ which are assigned as the energy loss equivalent of extended X-ray absorption fine structure (EXAFS).     

DasK-Röntgenemissionsspektrum des Chlors in freien Molekülen

TheKα andKβ spectra of chlorine in free molecules were studied using a special fluorescence X-ray tube and a high resolving curved crystal spectrograph with photoelectric registration. It was found that the wavelength shifts of ClKα₁ obtained for various gaseous compounds do not show the regularities observed with solid compounds of other 3rd period elements. — TheKβ spectrum consists of discrete lines the most intense of which result from transitions of the lonely pair electrons of the chlorine atoms. The spectra of HCl, Cl₂ and CH₃Cl can be explained using optical and betaspectroscopical data and MO calculations. The general structure of ClKβ of organic compounds seems to be determined by the hybridisation type of the carbon atoms bound to the chlorine atoms. Evidence is found for a contribution of molecular vibrational energy to the energies of the X-ray transitions.     

The photoelectron spectra of some iron tricarbonyl complexes of 4π-electron donor ligands

The photoelectron spectra of eighteen compounds which are dienes or diene—iron tricarbonyl complexes have been investigated. A comparison of the photoelectron spectra of the dienes and corresponding iron carbonyl complexes has yielded the values of the perturbation energies for the two π orbitals of the diene moiety caused by interaction with Fe(CO)₃. These perturbation energies are relatively constant (Δπ₁ = 0.89 ± 0.07 eV, Δπ₂ = 0.22 ± 0.06 eV) throughout the series. They have been employed to estimate the π ionization energies of the organic transient species cyclobutadiene (8.29 and 11.95 eV) and trimethylenemethane (8.36 and 11.79 eV), two novel molecules which have not been studied successfully by photoelectron spectroscopy to date.     

Electron impact spectra of some alkyl derivatives of water and related compounds

Electron impact energy loss spectra at impact energies of 100 eV and 50 eV and a scattering angle of 2 degrees are presented for alkyl derivatives of H₂O and related compounds. Spectra of H₂O, CH₃OH, CH₃OCH₃, ethylene oxide, CH₃CH₂OH, (CH₃)₂CHOH, (CH₃)₃C C₂H₅OC₂H₅ and tetrahydrofuran are tentatively assigned using derived term values and ionization potentials from photoelectron spectrosc Substituent effects on Rydberg orbital energies are discussed using Taft σ* values.     

Sum rule consideration on valence orbital ionization energies in methyl amines

A sum rule treatment using Hall's equivalent orbitals has been applied to the valence orbital ionization energies of mono-, di- and trimethylamine up to about 40 eV assuming Koopman's theorem. Excellent agreement is obtained between theory and experiment in partial and total energy sums. A similar treatment using p-type localized orbitals previously proposed by the authors is also applied to ionization energies below about 18 eV for the methyl amines. In these sum rule treatments we use both the vertical ionization energies obtained from He (I) photoelectron spectra measured here and the higher ionization energies deduced from the He (II) photoelectron spectra published by Potts et al. The complete sets of valence orbital ionization energies of the methyl amines have thus been identified by sum rule considerations in photoelectron spectroscopy. We show that the character of the corresponding MO's may be inferred from the sum rule. The orbital orderings and characters of the methyl amines have also been studied by CNDO/2 and MINDO/2 methods.     

An X-ray photoelectron spectroscopy study of volatile tin compounds

Core-level X-ray photoelectron spectra of fifteen compounds of tin have been measured in the gas phase. The compounds include various organo and halo compounds as well as tin(IV) nitrate and Sn{N[Si(CH₃)₃]₂}₂. The tin binding energies span a range of 4.4 eV and are well correlated by the “transition-state” point-charge potential model equation using atomic charges calculated by the CHELEQ electro-negativity equalization method. As expected, the empirically determined parameter k for tin is smaller than the k values obtained in previous work for carbon, silicon, and germanium. For Sn(NO₃)₄, and Sn{N[Si(CH₃)₃]₂}₂, the bonding can be described as a weighted average of several resonance structures. In these cases the binding energy data were used in conjunction with the CHELEQ method to determine the resonance structure weightings.     

Electron spectroscopy with excited atoms and photons.: X. Halogen-substituted methanes and methyl amines

Electron binding energy spectra have been measured for CH₃Cl, CH₃Br, CH₃I, CFCl₃, CF₂Cl₂, CF₃Cl, CF₄, CH₃NH₂, (CH₃)₂ NH and (CH₃)₃N. Measurements have been made using 584 Å (21.22 eV) photons as well as with 2³S(19.82 eV) and 2¹S(20.62 eV) metastable helium atoms. Relative spectral intensities are compared for photoionization and Penning ionization.     

Photoelectron spectra of F3SiC2H4Si(CH3)3 molecule using monochromatized synchrotron radiation

A variety of photoelectron spectra for gas phase F₃SiC₂H₄Si(CH₃)₃ molecule have been measured using monochromatized undulator radiation and a hemispherical electrostatic analyzer. Valence photoelectron spectrum shows many peaks for ionization from shallow and deep molecular orbitals in the binding energy region of 9–40 eV. A calculation of ionization energies using the outer valence Green's function method indicates energies in agreement with experimental results below 17.5 eV. Spectra for Si L-shell electron emission show chemical shifts of Si atoms induced from different chemical environments around two Si atoms and also exhibit spin–orbit splitting for 2p photoelectrons. Further photoelectron spectra for C K-shell and F K-shell are discussed in comparison with those of related molecules.     

Multiple-scattering calculations for 1s photoelectron angular distributions from single oriented molecules in the energy region above 50 eV

1s photoelectron angular distributions from fixed-in-space CO₂, NO₂, BF₃ and CH₃F molecules have been calculated by X-ray photoelectron diffraction (XPD) theory with muffin-tin-type molecular potential. For all the molecules, the calculated results show good agreements with those by density functional theory in the energy region ?100 eV. Furthermore, for all the molecules experimental data on the angular distributions in such energy region are well reproduced by the XPD theory. These intensive studies lead to a rather general rule that the XPD theory is an adequate tool to describe high-energy photoelectron angular distributions for any single oriented molecules.     

UV photoelectron spectra and sum rule consideration: Out-of-plane orbitals of unsaturated compounds with planar-skeleton structure

He(l) photoelectron spectra are presented for various planar unsaturated aliphatic compounds such as mono- and di-methyl substituted ethylenes, alkyl aldehydes, chloro-substituted aldehydes, ketones and alkyl acids. Each photoelectron spectrum is resolved into individual bands by considering the band shape, the relative intensity and the number of p-type localized MO's (LO's). The sum rule previously proposed on vertical ionization energies by the present authors is applied to the photoelectron bands associated with out-of-plane LO's. In each compound, a partial sum P(a″) is obtained over all the out-of-plane LO's and it is shown that the calculated P(a″) value is in good agreement with the experimental one which may be obtained by an appropriate sum of vertical ionization energies with negative signs.     

He(I) photoelectron spectroscopy of anions in adiponitrile solution

He(I) photoelectron spectra are reported of solutions of salts in adiponitrile in which peaks characteristic of the anions are visible; the vertical ionisation energies of these peaks are 6.91 and 7.85 (I^?), 7.6 (Br^?), 8.1 (Cl^?), 7.0 (CNS^?), 8.1 and 6.8 (NO₂^?), and 7.6eV (SO₄^2?). The salts examined were tetra-n-butyl ammonium (NO₂^?, I^?, Br^?, Cl^?, CNS^?, SO₄^2?), N-methylpyridinium I^?, trimethylphenylammonium I^?, choline I^?, methyltrioctylammonium I^? and methyltriphenylphosphonium Br^?. The relationship between these spectra and the charge transfer to solvent spectra of the anions is discussed.     

An XPS—AES study of gaseous xanthates and related sulfur-containing compounds

Core XPS spectra for carbon, oxygen, and sulfur and KLL Auger spectra for sulfur in CH₃OCS₂CH₃, (CH₃OCS₂)₂, CS₂, and OCS have been measured and relaxation shifts determined for the sulfur atoms by combining the S 1s measurement with the S KLL (¹D₂) measurement.Relaxation shifts of the sulfur atoms were also estimated from CNDO results for the neutral and core-ionized molecules using the equivalent cores approximation. The results are in qualitative agreement with the measurements, but exaggerate the relaxation by about 100%.The results show that the bonding of the (CH₃O-) group in the two xanthate compounds is very similar. The ionization energies of the S and -S- atoms within the xanthate molecules differ from each other by 1.5 eV; this difference arises almost entirely from the initial-state charge distribution rather than from final-state relaxation. However, the ionization energies of similarly bonded sulfur atoms are nearly the same. The effect of the oxygen atom on the bonding of the carbon and -S- atoms in the (-CS₂-) group in the xanthate compounds is to increase the (C 1s-S 2p_{$\text{3}\text{2}$}) ionization energy difference from the value reported for aliphatic disulfides.     

Photoelectron spectra and orbital assignments by sum rule consideration: Ethyl and n-propyl fluorides

The He I photoelectron (PE) spectra of C₂H₅F and n-C₃H₇F have been obtained. The PE spectra indicate that the first ionization potentials are about 0.4 eV higher than those of the parent alkanes owing to the inductive effect of fluorine. All the PE bands obtained here have been interpreted in terms of appropriate p-type localized MO's using the sum rule described previously by the authors. Orbital energy diagrams involving the inductive effect of fluorine are illustrated. The semi-empirical CNDO/2 and MINDO/2 methods were also employed to help confirm the present orbital assignments.     

光电子成像研究AgOCH3-和Ag-(CH3OH)x (x=1, 2)

用光电子成像技术和从头算法研究Ag^-(CH₃OH)_x (x=1, 2)和AgOCH₃^-. 从AgOCH₃^-振动分辨的光电子谱得 到AgOCH₃^-的绝热和垂直电离能分别为1.29(2)和1.34(2) eV. Ag^-(CH₃OH)_{1,2相似文献}   

(e, 2e) spectroscopy of N2—valence momentum distributions and configuration interaction

The noncoplanar symmetric (e, 2e) reaction has been applied to N₂ at 1200, 600 and 400 eV. Separation energy spectra are obtained in the valence region, the observed structure extending to above 60 eV. Electron momentum profiles are measured at a number of separation energies. They agree very well with the momentum distributions for valence orbitals given by SCF calculations. Considerable configuration interaction structure is observed, being primarily due to configuration interaction in the 2σ_g hole state. At 1200 eV the spectroscopic sum rule is satisfied within experimental error, confirming the validity of the analysis.     

UV and X-ray-excited photoelectron spectra of trifluoromethylgermanes (CF3)4−nGeHn(n = 1–3)

He(I), He(II) and X-ray-excited photoelectron spectra of the trifluoromethylgermanes (CF₃)_4?nGeH_n(n = 1–3) are reported. Assignments of the valence region are made on the basis of semi-empirical CNDO/2 calculations, comparisons with the spectra of related series of molecules, band shapes, and relative-intensity changes between features in the He(I) and He(II) spectra. Core-level binding energies are also compared with those of related species, and the usefulness of CNDO/2 and EESOP charge calculations is examined.     

用小角X射线散射法研究CH2Cl2,CHCl3和CCl4对磷脂酰胆碱液晶态结构的影响机理

本文采用小角X射线散射法分别研究CH₂Cl₂,CHCl₃和CCl₄对磷脂酰胆碱液晶态结构的影响机理,通过比较得知,CH₂Cl₂,CHCl₃和CCl₄对磷脂酰胆碱液晶态结构影响的不同之处,主要是它们空间旋转电子云密度分布不同所致,空间旋转电子云密度分布呈球状或椭球状的物质都有使磷脂酰胆碱液晶形成片层六角形的机理,呈圆锥状的物质有诱发磷 关键词：     

Chloromethane surface chemistry on Fe3O4(1 1 1)-(2 × 2): A thermal desorption spectrometry comparison of CCl4, CBr2Cl2, and CH2Cl2

The surface chemistry of CBr₂Cl₂ on the Fe₃O₄(1 1 1)-(2 × 2) selvedge of single-crystal α-Fe₂O₃(0 0 0 1) has been investigated using temperature programmed reaction and desorption (TPR/D) measurements. The spectra obtained in this case show that strong chemisorption occurs and that a series of adsorbed halogenated reaction products are present. By comparison, studies of the adsorbed phase of CH₂Cl₂ show that only physisorption occurs. The TPR/D spectra of CBr₂Cl₂ show that dissociative formation of CCl₂ followed by its reaction with lattice oxygen is central to the monolayer reaction chemistry in this chloromethane. The branching ratios of the various desorbed products are compared with those obtained from CCl₄ adsorbed on the same (2 × 2) surface.     

Ozone generation in oxygen-fed wire-to-cylinder ozonizer: effect of CH2Cl2, CHCl3 and CCl4 diluents

The inhibition effect of methylene chloride CH₂Cl₂, chloroform CHCl₃ and carbon tetrachloride CCl₄ on the ozone generation process from oxygen by negative corona discharge was experimentally investigated. The experiments were performed in a system of coaxial cylindrical electrodes at total gas pressure of 900 mbar and ambient temperature of gaseous mixtures. The rate of ozone generation as well as ozone concentration apparently decreases with a rising number of substituted chlorine atoms in the methane molecule at constant specific energy consumption dissipated in the discharge and at constant concentration of gaseous impurities in oxygen. In addition to experimental results, the paper presents theoretical considerations aimed at identifying the main process responsible for inhibition of ozone generation. The consumption of considerable fraction of oxygen atoms by CH _x Cl _y–1 radicals formed in discharge, is likely the most important mechanism responsible for the deleterious effect of such compounds on the efficiency of ozone production.     

Effect of the group IV elements on the Π anion and cation states of thiophene and furan determined by means of ETS and UPS

The electron-transmission and He(I) photoelectron spectra of Si(CH₃)₃, Sn(CH₃)₃ and CH₂Si(CH₃)₃ derivatives of thiophene and furan have been recorded. The first two substituents perturb the energies of the outer filled π orbitals and of the empty π* orbitals in opposite directions, causing a reduction of the HOMO/LUMO energy separation. The stabilization experienced by the π* MO's depends on their wavefunction coefficients at the site of substitution, and is attributed to interaction with low-lying empty orbitals of the substituent groups. The relatively small size (～ 0.4 eV) of this effect on the unoccupied ring MO's suggests that it should not appreciably affect the energy of the filled MO's.The strong conjugation between the π* unoccupied orbital of the nitro group and those of thiophene has also been investigated.