Relativistic atomic natural orbital type basis sets for the alkaline and alkaline-earth atoms applied to the ground-state potentials for the corresponding dimers

New basis sets of the atomic natural orbital (ANO) type have been developed for the atoms Li–Fr and Be–Ra. The ANOs have been obtained from the average density matrix of the ground states and the lowest excited states of the atom, the positive ion, and the dimer at its equilibirium geometry. Scalar realtivisitc effects are included through the use of a Douglas–Kroll Hamiltonian. Multiconfigurational wave functions have been used with dynamic correlation included using second-order perturbation theory (CASSCF/CASPT2). The basis sets are applied in calculations of the ground-state potentials for the dimers. Computed bond energies are accurate to within 0.05 eV for the alkaline dimers and 0.02 eV for the alkaline-earth dimers (except for Be₂).Acknowledgments.ensp;B.O.R. would like to express his gratitude to Prof. Jacopo Tomasi for all the inspiration that his scientific work has given him through the years and continues to do in particular through the work on solvent effects on molecular properties. This work has been supported by a grant from the Swedish Science Research Council, VR.Contribution to the Jacopo Tomasi Honorary Issue     

A data-acquisition system for the combination gas chromatograph-mass spectrometer

Summary A method for fast digital recording of low-resolution mass spectra has been developed. The method has been used for combination gas chromatography — mass spectrometry and allows, inter alia, on-line inspection of the data being recorded. Since the central unit of the acquisition system consists only of a multi-channel analyser, the system costs less than computer-based alternatives.The data recorded and processed can be displayed in a number of ways, usually after semi-automatic back-ground subtraction and normalisation. Interpretable data are then presented as tables or plotted diagrams, and are in computer-compatible form to allow later comparison with library-stored mass spectra.

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Ein Datenverarbeitungssystem zur Kombination Gas-Chromatograph-Massenspektrometer

Zusammenfassung Es wurde eine Methode zum schnellen digitalen Aufzeichnen von Massenspektren niedriger Auflösung entwickelt. Die Methode wurde für die Kombination Gas-Chromatographie — Massenspektrometrie verwendet. Sie erlaubt unter anderem eine on-line-Beobachtung der erfaßten Daten. Da die Zentraleinheit des Datenverarbeitungssystems nur aus einem Viel-Kanal-Analysator besteht, kostet das System weniger als andere, die auf einem Prozeßrechner basieren.Die erfaßten und verarbeiteten Daten können auf verschiedene Weise — gewöhnlich aber nach halbautomatischer Untergrundkorrektur und Normierung — dargestellt werden. Interpretierbare Daten werden dann in Form von Tabellen oder von Diagrammen dargestellt; sie sind in einer Form, die den Daten aus einem Prozeßrechner entspricht, so daß ein späterer Vergleich mit gespeicherten Massenspektren möglich ist.

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Un système de traitement de donnèes pour la combinaison chromatographe en phase gazeuse — spectromètre de masse

Sommaire On a mis au point une méthode pour l'enregistrement digital rapide de spectres de masse à faible résolution. La méthode a été employée pour la combinaison chromatographie en phase gazeuse — spectrométrie de masse. Entre autres, elle permet l'observation «on-line» des données enregistrées. Puisque l'unité centrale du système de traitement de données consiste seulement d'un analyseur multi-canal, le système est moins coûteux que d'autres basés sur l'emploid d'un ordinateur de procédé.Les données enregistrées et traitées peuvent être présentées de façon différente — mais généralement après correction semi-automatique du bruit de fond et standardisation subséquente. Les données qui se prêtent à l'interprétation sont alors présentées sous forme de tables ou de diagrammes; elles ont une forme qui correspond à celle des données fournies par un ordinateur de procédé, de sorte qu'une comparaison avec des spectres de masse déjà existants est rendue possible.

     

Collection and Determination of Mercury in Air

A method has been developed for the determination of low concentrations of mercury in air (nanograms/m³), i.e. in the range of the believed natural levels of mercury in the atmosphere (20 ng/m³). Mercury vapour has been collected from up to 200 1 of air in glass tubes containing thin films of gold on sieved ceramic powder. In the laboratory the absorbed mercury was then released into a quartz-window cell by heating the tube in an oven at 500°C.

In this paper it is demonstrated that, by using extremely thin films of precipitated gold, quantitative recovery is obtained and memory effects, which result from the use of thicker films, are avoided.     

A CASSCF-CI study of the coordination of ethylene with iron

Summary Complete active space SCF, CASSCF, and contracted CI calculations have been performed on the -bonded complex between ethylene and an iron atom. An extended basis set of the ANO type was used, which included polarization functions on all centers. The results indicate an attractive interaction between Fe ⁵ F(d⁷s) and ethylene, with an estimated binding energy of 14 kcal/mol. The low spin complex arising from Fe ³ F(d⁷s) was found to be bound with 18 kcal/mol. Both these potential minima are, however, above the ground state of the iron atom. It is concluded that the interaction between atomic ground state iron and ethylene is not of the normal -bonded type, but is dominated by dispersion forces. A preliminary study showed this interaction to be almost isotropic, with no preferred site for the iron atom.     

On the philosophy of optimizing contrast agents. An analysis of 1H NMRD profiles and ESR lineshapes of the Gd(III)complex MS-325+HSA

A generalization of the modified SBM theory is developed in closed analytical form. The theory is applied to describe the paramagnetically enhanced water proton spin-lattice relaxation rates of the aqueous-systems containing a gadolinium(S=7/2) complex(MS-325) in the presence or absence of human serum albumin (HSA). MS-325 binds to HSA: in the absence of the protein the reorientational time, tauR, is short, but when HSA is added tauR becomes much longer. In this way, the effect of reorientational motion, static (Delta s), and transient (Delta t) zero-field splitting (ZFS) interactions on both the water proton relaxivity and the Gd ESR lineshapes are investigated. Two dynamic models of electron spin relaxation are presented, characterized by transient and static ZFS-interactions. X-, Q-, and W-bands ESR spectra of MS-325+HSA are analyzed in order to describe the effect on the electron spin system upon binding to a macromolecule. A computer program based on this theory is developed which calculates solvent water proton T1 NMRD profiles and the corresponding X-, Q-, U-, and W-bands ESR lineshapes.     

Eine Modifikation der Niclouxschen Methode zur Bestimmung von ?thylalkohol

Ohne Zusammenfassung     

Benzoes?ure

Ohne Zusammenfassung