Angle-resolved X-ray fluorescence spectrometry using synchrotron radiation at ELSA

Measurements on the centroid depth of ion-implanted phosphorus-in-silicon specimen by the method of angle-resolved, self-ratio X-ray fluorescence spectrometry (AR/SR/XFS) have been carried out using white synchrotron radiation (SR). The measurements were performed using a modified wavelength-dispersive fluorescence spectrometer. Problems due to the use of SR, like carbonaceous specimen contamination and sample heating were overcome by flooding the specimen chamber with helium and by pre-absorbing the non-exciting parts of the incident SR with suitable filters, respectively. The decaying primary intensity was monitored by measuring the compensation current of the photoelectrons emitted from a tungsten wire stretched across the primary beam. Results have been obtained for specimen with dose density levels of 10¹⁶ cm^–2 and 3×10¹⁵ cm^–2.     

Characterization of ion-implanted silicion by Rutherford backscattering spectrometry and ellipsometry

It is demonstrated that the information obtained by Rutherford backscattering spectrometry and channeling technique can substantially help in the construction of a realistic optical model for the ellipsometry of ion-implanted silicon. In the case of fully amorphous ion-bombarded layers, the ellipsometry is a fast, non-destructive and contactless method to estimate the thickness of these films. For buried and partially disordered layers a qualitative interpretation of different trajectories in the - plance can be given on the basis of channeling measurements.     

Thermal membrane potential across cation-exchange membranes for various halide solutions

Thermal membrane potential across cation-exchange membranes was measured for various halide solutions. Linear relationships between thermal membrane potential () and temperature difference (T) were observed, and the temperature coefficient of thermal membrane potential (/T) decreases with increase in the molality of the external solution as predicted by a theory reported. When counterions of membranes are hydrogen ions, the sign of the coefficients turns into minus near 0.01 mol/kg of the external solution for all membranes, although the coefficients are always positive for all the other forms. The dependence of the coefficients on the molality of the external solutions sometimes deviated slightly from the theory. This deviation is attributed to some change in water content of the membranes. A reproducible method of measuring water content of membranes was applied to discuss the change in the state of the membranes.     

Evaluation of dissociation constants of ammonium ion in aqueous lithium perchlorate and lithium chloride-sodium chloride mixed solutions

The Pitzer approach has been applied to the evaluation of dissociation constants of ammonium ion in lithium perchlorate and lithium chloride-sodium chloride mixed solutions at 25°C. The calculated values showed good agreement with the observed values, provided all the higher-order interaction terms ('s and 's) concerned were introduced. The unknown (NH₄LiClO₄) value was determined from the isopiestic measurements of NH₄ClO₄–LiClO₄ mixed solutions. Parameters in the Pitzer formalism for ammonia-ion interactions involved in LiCl and NaCl media were determined by use of the activity coefficients of ammonia measured in LiCl–NaCl mixed solutions by a transpiration method.     

Hypervirial theorems and symmetry

It is pointed out that to ensure that an optimal variational wave function having a certain symmetry satisfies the hypervirial theorem forW, it is sufficient thatiSW, whereS is the projector onto the symmetry type in question, be a possible variation of . Application is made to the tensor hypervirial theorem for atoms.     

The effect of alkyl groups on the electronic spectra of benzenoid hydrocarbons

Alkyl substitution of benzenoid hydrocarbons shifts their ¹ L band to longer wavelengths. A statistical analysis of the available data for naphthalene, phenanthrene and 1,2-benzanthracene indicates that simple Hückel theory does not yield as good a prediction for these shifts as has previously been assumed. It is shown that a significant improvement results if many electron wavefunctions are used and if mixing between the configurations ₁ ^–1 and ₂ ^–2 is introduced.

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Zusammenfassung Unter dem Einfluß von Alkylsubstituenten verschiebt sich die ¹ L Bande aromatischer Kohlenwasserstoffe nach längeren Wellenlängen. Eine statistische Analyse der Daten für Naphthalin, Phenanthren und 1,2-Benzanthracen deutet darauf hin, daß das einfache Hückelsche Verfahren weniger gute Voraussagen dieser Verschiebungen liefert, als allgemein angenommen wird. Es kann gezeigt werden, daß die Verwendung von Mehrelektronen-Wellenfunktionen und die Einbeziehung der Wechselwirkung zwischen den Konfigurationen ₁ ^–1 und ₂ ^–2 einer signifikanten Verbesserung der Voraussagen führt.

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Résumé L'introduction d'un groupe alkyle sur un hydrocarbure benzènoïde provoque un déplacement de la bande ¹ L vers les grandes longueurs d'onde. Une analyse statistique des données existant pour le naphthalene, le phénanthrène et le 1,2-benzanthracène montre que la simple théorie de Hückel ne permet pas de prévoir ce déplacement aussi exactement qu'on l'admet en général. L'utilisation de fonctions d'onde polyélectroniques et l'introduction de l'interaction entre les configurations ₁ ^–1 et ₂ ^–2 conduit, au contraire, à une amélioration significative des résultats.

     

Allowance for electron correlation in calculations of the magnetic properties of molecules by variation of the vector potential

Conclusion The results which we have obtained indicate that when moderately accurate nonperturbed wavefunctions of the electron pairs ^(o) are used, the simplified approach based on Eq. (11) is quite sufficient. The correlation gradient transformations, for which the variables of different electrons are not separated in the function F(r₁, r₂), become important only in precision calculations of the magnetic susceptibilities (for a required accuracy of the order of 0.1% and below), which have to be carried out with extremely accurate nonperturbed wavefunctions ^(o). Finally, it should be remembered that our conclusions apply directly to two-electron systems, described by nodeless nonperturbed coordinated wavefunctions ^(o). When the functions ^(o) have nodal surfaces (or when the number of electrons in the system is increased), the vector potential variation problem becomes more complicated.Translated from Zhurnal Strukturnoi Khimii, Vol. 25, No. 1, pp. 13–18, January–February, 1984.     

The convergence of the Rayleigh-Ritz Method in quantum chemistry

Two sufficient criteria for the convergence of the Rayleigh-Ritz Method (RRM) with respect to the eigenvalues (E-convergence) of non-relativistic electronic Hamiltonians of molecules are discussed and compared. Moreover, a necessary and sufficient criterion is given. By example (Sect. 9) it is shown that the L ²-completeness of the basis is not sufficient to guarantee E-convergence. The convergence of the wave functions in different norms (-convergence) is also investigated. In particular, sufficient conditions for the one-particle basis functions (orbitals) are given, such that a CI calculation in this basis is both E- and -convergent.     

Single-Ion Contributions to Activity Coefficient Derivatives, Second Moment Coefficients, and the Liquid Junction Potential

We discuss several interrelated single-ion thermodynamic properties required to calculate the liquid junction potential between two solutions of the same binary electrolyte. According to a previously reported molecular theory of nonuniform electrolyte solutions in nonequilibrium, is determined by the transport numbers of the ions, and by the second moment coefficients H ⁽²⁾ of the charge densities around the ions. The latter may be viewed as the single-ion contributors to the second moment condition of Stillinger and Lovett. For a solution of a single binary electrolyte, we relate the H ⁽²⁾ (R) to the derivatives of the single-ion activity coefficients with respect to the ionic strength. In the light of these results, we examine, in some detail, the role played by the specific short-range interionic interactions in determining . We investigate this matter by means of integral equation calculations for realistic models of LiCl and NaCl aqueous solutions in the 0–1 mol-dm^–3 range. In addition to the hypernetted-chain (HNC) relation, we perform calculations under a new integral equation closure that is a hybrid between the HNC and Percus–Yevick closures. Like the HNC approximation, the new closure satisfies the Stillinger and Lovett condition. However, for the models considered in this study, the two closures predict different dependence of the H ⁽²⁾ and of on the specific part of the interionic interactions.     

Molecular orbital calculations on the conformation of polypeptides and proteins

The conformational energy maps are computed for the lysyl and the arginyl residues with the help of the quantum-mechanical method PCILO. Because of the relatively very large number of the possible combinations of the side chain rotational angles, sub-maps are constructed only for the most common such combinations as indicated from the X-rays study of ten globular proteins. These submaps are then combined for the construction of the general conformational energy map. The comparison of the theoretically allowed and experimentally observed values of backbone dihedral angles and for the lysyl and arginyl residues in the globular proteins indicates a very satisfactory agreement among the two. These results confirm that the contour of the stable zone on the conformational energy map depends primarily on ¹ but indicate also that its fine structure is sensitive to the remaining 's in particular to ².

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Zusammenfassung Diagramme der Konformationsenergie werden für den Lysyl- sowie den Arginylrest mit Hilfe der quantenmechanischen PCILO-Methode berechnet. Wegen der großen Zahl möglicher Kombinationen der Rotationswinkel der Seitenketten werden Teildiagramme nur für die wichtigsten derartigen Kombinationen, die bei Untersuchungen nach der Röntgenstrahlmethode an zehn globulären Proteinen gefunden wurden, konstruiert. Diese Teildiagramme werden dann zum Gesamtdiagramm der Konformationsenergie kombiniert. Die Übereinstimmung zwischen experimentellen und theoretisch erlaubten Winkeln und der Hauptkette und den Lysyl- und Arginylresten ist sehr zufriedenstellend. Diese Ergebnisse bestätigen, daß der stabile Bereich des Diagramms der Konformationsenergie hauptsächlich von ¹ abhängt; sie zeigen aber auch, daß seine genaue Struktur von den übrigen -Werten beeinflußt wird, insbesondere von ².

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Résumé Les cartes d'énergie conformationelle des résidus lysyle et arginyle sont construites à l'aide de la méthode PCILO de la Chimie Quantique. A cause du nombre très élevé des combinaisons possibles des angles rotationnels de la chaîne latérale, des sous-cartes sont construites pour les plus fréquentes seulement de ces combinaisons (selon les indications de l'étude aux rayons X de dix protéines globulaires). Ces sous-cartes sont ensuite combinées pour la construction de la carte générale d'énergie conformationnelle. La comparaison des valeurs théoriques et expérimentales des angles et de la chaîne principale pour les résidus lysyle et arginyle des protéines indique un accord très satisfaisant entre les deux. Ces résultats confirment que le contour de la zone stable sur la carte d'énergie conformationnelle est déterminé principalement par la valeur de ₁ mais indiquent aussi que la structure fine de cette zone est sensible aux valeurs des supérieurs, en particulier de ².

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This work was supported by grant n 67-00-532 of the Délégation Générale à la Recherche Scientifique et Technique (Comité de Biologie Moléculaire).     

Background levels of uranium in human urine

The literature on the normal content of uranium in urine is reviewed. The reported normal concentration has declined several orders of magnitude over the years, probably due to improvements in analytical technique rather than a real change. The lowest mean values were reported with spectrometry (mean of 23 ng/l in 12 subjects) and thermal ion mass spectrometry (3.4 ng/l in 1 subject). Even spectrometry is not sufficiently sensitive at normal levels, so that techniques such as fission track analysis or mass spectrometry must be used to obtain results above the detection limit of the technique for individual samples.     

Determination of boron by the neutron depth profile (NDP) technique for VLSI processing application

Borophosphosilicate glass (BPSG) has been used for its improved reflow properties compared to low temperature oxide (LTO) in planar technology. Thin films of BPSG were deposited by a low-pressure chemical vapor deposition process. The boron content was determined by NDP. In addition from the NDP spectrum the depth profile of boron and the thickness of the film were also determined. In the NDP technique, samples, typically silicon wafers with 500 nm thick BPSG film, were exposed to a highly-thermalized neutron beam. Generated by the¹⁰B(n,)⁷ Li reaction, isotropically emitted monoenergetic particles of 1.47 MeV were counted in an evacuated in-beam analysis setup. The energy loss of the -articles in the film was proportional to the depth at which the nuclear reaction took place. The energy spectrum of the -articles, therefore, was a direct result of the boron depth profile, and the area under the curve was a measure of the total number of boron atoms in the film. This unique nuclear technique provided an excellent method for optimizing the composition of the BPSG film for device processing.     

Generalized quantum mechanical two-centre problems. IV. On the accuracy of simple LCAO approximations for H 2 + states and the Eckart criterion

If x denotes an exact solution of the quantum mechanical two centre Coulomb problem, we optimize a normalized LCAO approximation by making the overlap S = (x¦) a maximum. In this context we study how a weight factor (r _a r _b )^–1 in the definition of the inner product changes the approximation and the expectation value of electronic energy. Finally we compare the lower bound given by the Eckart criterion with the exact overlap. Results are reported for H ₂ ⁺ states 1s_g and 2p_u.Dedicated to Professor Hermann Hartmann on occasion of his 70th birthday on May 4th, 1984     

Double dimethylammonium sulphates of Tb,Dy, Ho,Er, Tm,Yb, Lu and Y

Double sulphates of rare earths with dimethylammonium, with empirical formula (CH₃)₂NH₂Ln(SO₄)₂·4H₂O (Ln=Tb, Dy, Ho, Er, Tm, Yb, Lu and Y), were studied by means of thermogravimetry, derivative thermogravimetry and differential thermal analysis from 20 to 700°. Quantitative gravimetric analysis was used for the determination of rare earths and sulphate. The mechanism of thermal decomposition is also suggested.

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Zusammenfassung Doppelsulfate der seltenen Erden mit Dimethylammoniumionen der empirischen Formel (CH₃)₂NH₂Ln(SO₄)₂·4H₂O (Ln=Tb, Dy, Ho, Er, Tm, Yb, Lu und Y) wurden mittels TG, DTG und DTA im Temperaturbereich von 20–700° untersucht. Die Seltenen Erden und Sulfat wurden gravimetrisch bestimmt. Ein Mechanismus der thermischen Zersetzung wird vorgeschlagen.

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, 20–700° (₃)₂N₂Ln(S₄)₂·4₂, Ln=Tb, Dy, , Er, Tm, Yb, Lu Y. . .

     

Effect of the EDL Structure on the Mechanism of Electroreduction of Adsorbed Intermediates

Effect of the ₁ potential on various kinetic modes of the -hydroxyethyl radical reduction is studied using laser photoemission (LPE). A charged proton donor is found to make no impact on the electron transfer rate during the reduction of adsorbed radicals. Experimental results fit the model proposed earlier for the electroreduction of intermediates, which includes two parallel pathways for electron transfer—onto an adsorbed radical and onto a metastable complex radical–proton donor. Demonstrated is a complete analogy between time-resolved voltammograms for LPE-generated intermediates and classic polarograms.     

Evaluation of Multicenter Electronic Attraction, Electric Field and Electric Field Gradient Integrals with Screened and Nonscreened Coulomb Potentials over Integer and Noninteger n Slater Orbitals

By the use of complete orthonormal sets of -exponential-type orbitals, where ( = 1, 0, –1, –2,...) the multicenter electronic attraction (EA), electric field (EF) and electric field gradient (EFG) integrals of nonscreened and Yukawa-like screened Coulomb potentials are expressed through the two-center overlap integrals with the same screening constants and the auxiliary functions introduced in our previous paper (I.I. Guseinov, J. Phys. B, 3 (1970) 1399). The recurrence relations for auxiliary functions are useful for the calculation of multicenter EA, EF and EFG integrals for arbitrary integer and noninteger values of principal quantum numbers, screening constants, and location of slater-type orbitals. The convergence of the series is tested by calculating concrete cases.     

New data obtained by thermomagnetometry,on the phase transitions in Ni,Co, Pt,Cu and Fe-C alloys

On the basis of thermomagnetic and DTA measurements, together with data from the literature, it may be concluded that in some f.c.c. metals a phase transformation occurs just before melting.

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Zusammenfassung Auf Grund thermomagnetischer und differentialthermoanalytischer Messungen sowie Literaturangaben wird geschlossen, dass in manchen kubisch-flächenzentrierten Metallen wenig unterhalb der Schmelztemperatur eine reversible Phasenumwandlung, wahrscheinlich in eine kubischraumzentrierte oder amorphe Phase, stattfindet.

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, , , .

     

Structural Study of Methyl Acrylate in a Nematic Liquid Crystal by 1H NMR with 13C Satellites

The molecular structure and conformation of methyl acrylate have been determined by analyzing the ¹H NMR spectrum with ¹³C satellites of the molecules dissolved in the liquid crystal ZLI 1132. In the structural analysis, direct coupling constants have been corrected for molecular vibrations and converted to those in the r structure. The correlation between reorientational motion and internal rotation has been taken into account by using the mean external potential described in terms of bond interaction tensors. The potential for the internal rotation about the bond has been represented as V() = (V ₁/2) (1 – cos ) + (V ₂/2)(1 – cos 2), where is zero for the s-cis configuration, and the determined values of V ₁ and V ₂ are 2.7(1) and 8.4(13) kJ mol^–1, respectively. The relative abundance of the s-cis conformer, 76(1)%, agrees with a gas-phase value, 67(11)%, determined by electron diffraction within experimental errors.     

Simultaneous TG,DTG, DTA and EGA technique for the determination of carbonate,sulphate, pyrite and organic material in minerals,soils and rocks

A simultaneous TG, DTG, DTA and EGA method was developed for the determination of carbonate, sulphate, pyrite and organic material in minerals. The method is based on the selective direct determination of SO₃ and CO₂ evolved from the heated sample, and on the indirect determination of H₂O. The thermogas-titrimetric adapter of the derivatograph collects the liberated gases (CO₂, SO₃, SO₂) quantitatively, absorbs them in water, and titrates them continuously and automatically with NaOH titrant. The changes in the volume of titrant consumed are recorded as a function of the temperature. In two parallel examinations, one titration is performed at pH 4, and the other at pH 9.3. The former measurement yields only the amount of SO₃ (SO₂), while the latter gives the joint amount of SO₃ (SO₂) and CO₂.

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Zusammenfassung Autoren entwickelten eine Methode zur simultanen TG, DTG, DTA und EGA zur Bestimmung von Karbonaten, Sulfaten Pyrit und organischem Material in Mineralen. Die Methode basiert auf der selektiven direkten Bestimmung des beim Erhitzen der Probe entwickelten SO₃ bzw. CO₂ und der indirekten Bestimmung von Wasser. Die in Freiheit gesetzten Gase (CO₂, SO₃, SO₂) werden im gastitrimetrischen Adapter des Derivatographen gesammelt, in Wasser absorbiert und kontinuierlich und automatisch mit NaOH titriert. Das Volumen der verbrauchten Titrierflüssigkeit wird in Abhängigkeit von der Temperatur registriert. In zwei Parallelversuchen wird eine Titration bei pH 4, die andere bei pH 9.3 ausgeführt. Die erstere Messung ergibt nur die Menge an SO₃ (SO₂), während bei der letzteren die Gesamtmenge an SO₃ (SO₂) und CO₂ erhalten wird.

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, , ( ) , , . SO₃ CO₂, , . - (CO₂, SO₃, SO₂), . ë . : pH=4, - pH=9.3. SO₃(SO₂), — SO₃(SO₂) CO₂.

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The authors thank Prof. E. Pungor for valuable discussions, and Mrs. M. Kiss and Miss I. Fábián for their technical assistance.     

New method for obtaining 5-pyrazolones

A new preparative method for obtaining 5-pyrazolones from N,N-dimethyl-N,N-diacylhydrazines that is based on the intramolecular formation of a C₍₃₎-C₍₄₎ bond in the pyrazolone molecule was developed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 933–936, July, 1991.