ESCA studies of some copper and silver selenides

Photoelectron and Auger spectra have been obtained for the copper and silver selenides CuSe, Cu ₂Se, Ag ₂Se, and AgCuSe as well as from CuS, Ag ₂O, Ag ₂S, Cu, and Ag. Binding-energy values, chemical shifts, and peak-shapes are reported for the Cu 3 d, Ag 4 d and Se 3 p electrons. Absence of multiplet splitting and shake-up structure is discussed in relation to the magnetic properties. It is shown that chemical shifts are much better revealed in the Auger spectra (Cu L₃M_4,5M_{4, 5} and Ag M₅N_{4, 5}N_{4, 5}) than in the direct photoelectron ones. In addition the use of the Auger parameter to characterize the series under study is emphasized. Finally the valence-band spectra have been examined and the electronic structures are interpreted.     

An ESCA study of organosilicon compounds

The silicon 2p electron binding energies have been measured for a series of 33 organosilicon compounds. The binding energies are correlated with partial atomic charges calculated by various electronegativity models and CNDO calculations. Group shifts are reported for various chemical groups attached to silicon and are found to correlate with group shifts reported for carbon and phosphorus compounds.     

ESCA studies of Cr-Co alloys

ESCA examination of films formed on Cr-Co alloys after immersion in 0.1M NaCl for 24 h has shown that the thickness of passive films decreased with an increase in chromium content. Surface films consisted of chromium and cobalt oxides as Cr₂O₃ and CoO. The amount of CoO in the surface film of the alloy was decreased with an increase in chromium but Cr₂O₃ was found at a greater depth in the passive film at any composition. Cr₂O₃ was a major component of the surface film when the chromium content in the alloy was 10% or higher. Electrochemical techniques according to ASTM G59 and ASTM G5 were used for the determination of the relative corrosion rate. Both Co-10 wt.% Cr and Co-30 wt.% Cr alloys investigated showed a lower corrosion rate than the Co-5 wt.% Cr alloy. Corrosion rate measured could be correlated to the surface film composition and structure as determined by ESCA.     

ESCA studies of Fe-Ti alloys

Fe-Ti alloys containing 5 to 47% Ti have been studied by ESCA. The alloys were exposed to 0.1 M NaCl for 24 h under open-circuit potential (OCP) during which passive films were formed. The passive film consisted of FeO and TiO₂ in the inner layer while Fe₂O₃, water, and hydroxyl groups were present in the outermost monolayers, irrespective of composition. The thickness of the passive layer was reduced from 4.4 nm to 1.0 nm with increasing Ti content. The amount of iron oxide in the passive layer also decreased with increasing Ti. Electrochemical techniques according to ASTM G59 and ASTM G5 were used for the determination of the relative corrosion rate of the alloys. Alloys with 5–28% Ti showed a relatively high corrosion rate but that with 47 wt.% Ti had a much lower corrosion rates.     

ESCA studies of Ni-Cr alloys

ESCA examination on Ni-Cr alloys has shown that a thin passive film was formed after 24 h immersion in 0.1 M NaCl. The film contained only chromium oxide in the form of Cr₂O₃. Electrochemical techniques according to ASTM G59 and ASTM G5 were used for the determination of the relative corrosion rate of the alloys. Both Ni-10 wt. % Cr and Ni-20 wt. % Cr alloys showed a slightly higher corrosion rate than the Ni-40 wt. % Cr alloy.The present ESCA study of the Ni-Cr system is part of our programme which involves an examination of the four binary alloy systems Fe-Si, Cr-Co, Ni-Cr, and Mo-Ni [1]. The aim is to correlate the structure and composition of the passive films formed in 0.1 M NaCl to the corrosion behaviour in the same solution.     

ESCA studies of Si-Fe alloys

ESCA examination of films formed on Si-Fe alloys after immersion in 0.1 M NaCl for 24 h has hown that the thickness of passive films decreased with an increase in silicon content. A thick passive film containing oxidized silicon and oxidized iron was formed on Fe-20 wt% Si and the oxidized iron was about three times higher than the oxidized silicon in the passive film. However, an obvious reduction in the oxidized iron in the film on Fe-30 wt % Si was observed. Oxidized iron was detected up to a depth of 1.0 nm and at a depth greater than 1.0 nm from the surface, the film was exclusively in oxidized silicon. The film was exclusively silicon oxide when the silicon content was increased to 50 wt %. Electrochemical techniques according to ASTM G59 and ASTM G5 were used for the determination of the relative corrosion rate. Fe-50 wt % Si was found to have a corrosion rate smaller than those lower silicon alloys. This relates to the surface film composition and structure as determined by ESCA.     

ESCA studies of nitrogen-containing stainless steels

ESCA examination of films formed on nitrogen-containing stainless steels after immersion in 0.1 M NaCl revealed that nitrogen was enriched in the outer 0.5 nm of the film at a concentration a few times higher than in the substrate. The N(1s) binding energy varied from 399.6–399.7 eV at the outermost surface of the film to 398.3–398.8 eV in the film at a depth of about 0.5 nm. This indicates a change in the chemical state of nitrogen upon exposure of the nitrogen-containing stainless steels to the solution, and furthermore, that the surface nitrogen enrichment could be of significance in the improved pitting resistance.     

An ESCA investigation of some copper complexes

A series of copper complexes have been investigated by ESCA. All complexes were salts of the tetraphenylphosphonium ion. The binding energies of all the atoms in the complexes were determined. From the binding energies of the ligand atoms we estimated the effective charges on these atoms. For this purpose we used linear relations of the formE_b = kq + E_bO which had been established previously within our scheme of C 1s (phenyl) as internal standard. From the data thus obtained, the effective charge on the copper atom was estimated. A linear relation between binding energy and the effective charge on the copper atom was found, i.e.,E_b(Cu) = 1.52q_Cu + 932.2ESCA spectra were recorded for the complexes bis(1,3-diphenyl-1,3-propanediono) copper (II) and bis(3-phenyl-2,4-pentanediono) copper (II). By a combination of the XPS binding energies and IR intensities of the ν_CH vibrations of the phenyl groups in the complexes with empirical relations between these entities and the effective charges of the atoms and groups, a fairly complete mapping of the charge distributions of these complexes has been achieved.     

An ESCA investigation of some thiocyanato complexes

A series of simple thiocyanato complex ions have been investigated as their tetraphenylphosphonium and potassium salts. The binding energies of N, C and S were determined as well as those of the metals. From the first-mentioned data effective charge-values were estimated for the atoms of the ligands. For this purpose linear relations E_b = kq + E_b0 were used that had been previously established within a scheme having C_1s (phenyl) as the internal standard.From the data thus obtained the effective charge on the metal atoms was estimated. For elements where we have sufficient data the same type of linear relation seems to he followed. Tentatively valid examples are E_b(Ni) = 6.74q_Ni + 848.3 eV and E_b(Pd) = 4.45q_Pd + 333.9 eV.In this interpretation the atoms of the metals are considered to be positively charged and surrounded by the negative charge of the electrons occupying the s band.It is further suggested for complexes with pronounced π backbonding (Pt(SCN)₄^2?, Pd(SCN)₄^2? and Hg(SCN)₄^2?) that the C 1s binding energy measured for the carbon atom of the SCN^? ligand is composed of the ionisation energy from the 1s level and an additional term corresponding to the intraligand π → π* transition.     

An ESCA investigation of some dithiooxalato complexes

A series of dithiooxalato complex ions have been investigated as their tetraphenyl-phosphonium and potassium salts. Core-electron binding energies (E_b) of S, C, and O were determined, as well as those of the metals. From the first-mentioned data, effective charge values (q) were estimated for the atoms of the ligands. For this purpose linear relations (E_b = k · q + E_bO) were used that had been previously derived within a scheme using C ls (phenyl) as the internal standard. From the data thus obtained the effective charge on the metal atoms could be estimated. The data is used to test if analogous linear relations also hold for the heavy elements; for example, we have found E_b(Pt) = 3.17 · q_pt + 71.1 eV.     

Recent progress in ESCA studies of gases

The development during the most recent years of ESCA applied to free molecules is reviewed. The advantages of studying, when possible, a substance in t     

ESCA studies of oxygen adsorption on nickel

A metallic nickel foil was studied by ESCA. The Ni 2p electron spectrum was characteristic of a mixture of nickel oxide and metallic nickel. Two ox     

ESCA studies of fracture surfaces in welded metals

A fracture device for ESCA studies of internal surfaces in metals is described. By fracturing a specimen under UHV, an uncontaminated surface is obtain The specimen is cooled to produce cleavage or intergranular fracture, depending upon the type of information sought.The technique has been applied to weldments in steels of composition C 0.020, Mn 1.15. In the as-welded state, fracture surfaces yield signals of C, N, and O as well as iron in oxidized state beside metallic iron. Antimony is found on the fracture surface of specimens embrittled by long annealing in ox A strong chemical shift indicates that it is present in the oxidized state.     

ESCA studies of chemical shifts for metal oxides

The binding energy shifts of some 35 elements on formation of an oxide have been measured by X-Ray Photoelectron Spectroscopy. When these are plotted against the atomic numbers of the elements or against the heat of formation of the oxides, characteristic trends can be observed, for the interpretation of which a number of rules of general validity may be drawn up.     

A new method for ESCA studies of liquid-phase samples

A new technique is described for obtaining ESCA spectra from liquid-phase samples. It combines temperature regulation of the liquid samples, which are continuously created as thin films on a metal backing, with the use of monochromatized A1 Kα radiation for excitation. The technique is simple to implement and can be used routinely over essentially unlimited periods of recording time in the spectrometer. The results show substantially increased quality with respect to earlier measurements in terms of signal-to-background ratio and resolution. The technique also implies a vast increase in the number of solvents usable for future liquid-phase ESCA work.     

Solid-state NMR studies of some tin(II) compounds

High-resolution NMR spectra of [Formula: see text] nuclei, particularly (119)Sn and (31)P, in solid tin(II) phosphite, SnHPO(3), and tin(II) phosphate, SnHPO(4), are presented. The results are discussed in relation to the crystal structures. Spinning sideband analysis has been carried out for both nuclei, giving information on the shielding tensors. Satellite peaks allow the indirect Sn,Sn coupling constants to be determined. Surprisingly large values of 2600+/-200Hz and 4150+/-200Hz are reported for SnHPO(3) and SnHPO(4) respectively. The satellite peaks were investigated by using a single Hahn echo for each refocusing time, which showed that the observed splittings result from (119)Sn, (117)Sn coupling. For SnHPO(3), the calculated relative intensities of the satellites for six intra-layer coupling interactions are in agreement with the experiment values, but for SnHPO(4) the coupling appears to be inter-layer in nature. Tin-119 (and in one case phosphorus-31) shielding tensor data derived from MAS NMR are also reported for four other crystalline tin(II) compounds, namely tin diphosphate, tin oxalate, tin sulphate and calcium tin ethylenediamine tetraacetate.     

Mössbauer effect studies of some trimeric iron compounds

Mössbauer spectra of some basic iron (III) carboxylates are reported. The zero field spectra are quadrupole doublets with a characteristic temperature dependent asymmetry. In applied magnetic fields at 4·2°K large hyperfine magnetic fields are observed. These can only result from a Hamiltonian which is not symmetric in all three sites. This asymmetry may be due to a structural asymmetry or to small intercluster magnetic interactions.