The visible absorption spectrum of NO2: A three-mode nuclear dynamics investigation

The vibronic band origins of the visible absorption spectrum of NO₂ are calculated theoretically with the aid of a simple model Hamiltonian for the coupled electronic and vibrational motions. Including all three vibrational modes in the calculation and using ab initio values of the relevant parameters, we obtain satisfactory qualitative agreement with experiment. In particular, the observed high density and irregular intensity distribution of the band origins is reproduced correctly by the calculation. The present results confirm unambiguosly that the anomalous vibronic structure of the ${}^2\text{B}{}_2\text{←}{}^2\text{A}{}_1$ transition is caused by strong nonadiabatic interactions between the ²B₂ and ²A₁ electronic states of NO₂. They also show that simple deconvolution procedures, which are often used to deperturb irregular spectra, are not applicable to the ${}^2\text{B}{}_2\text{←}{}^2\text{A}{}_1$ transition of NO₂. To further explore the strength of the nonadiabatic effects in NO₂, we calculate the mixing of the different electronic species in the vibronic eigenstates and compare it to several relevant experimental quantities.     

Stereochemie von Metallocenen, 10. Mitt.: Chemische Korrelation von α- und β-substituierten Methylferrocenen; die absolute Konfiguration optisch aktiver, β-substituierter Methyl- und 1.1′-Dimethylferrocene

Zusammenfassung Optisch aktive Methylferrocen-- und--carbonsäuren wurden über die entsprechenden isomeren Methylferroceno[1.2]-cyclohexenone (7, 12 und15, deren Struktur u. a. durchNMR geklärt wurde) und über ein aktives Methylferroceno-cyclohexen (8) bezüglich ihrer Konfigurationen chemische korreliert. ORD-Vergleiche der methylierten Ringketone mit Ferrocenocyclohexenon (10), dessen Konfiguration bekannt war, erlaubten einen sicheren Schluß auf die Konfigurationen aller - und -substituierten Methylferrocene: (1S) für die rechtsdrehenden Säuren und ihre Derivate. Dies konnte auch durch unabhängige Konfigurationsermittlung eines der Ringketone (12) bestätigt werden.Es sind damit die absoluten Konfigurationen von insgesamt 86 optisch aktiven - und -substituierten Ferrocenderivaten bekannt; alle Konfigurationen sind jetzt eindeutig miteinander verknüpft.

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Optically active methylferrocene-- and--carboxylic acids were configurationally correlated by chemical methodsvia the corresponding isomeric methylferroceno[1.2]cyclohexenones (7, 12 and15, the structures of which were elucidated among other methods byNMR) andvia an optically active methylferrocenocyclohexene (8).Comparison of theORD-curves of the methylated ringketones with ferrocenocyclohexenone (10), the configuration of which was known, allowed a reliable conclusion to the configurations of all - and -substituted methylferrocenes: (1S) for the dextrorotatory carboxylic acids and their derivatives. This result could also be confirmed by an independent determination of the configuration of one of the ring ketones (12).Thereby, the absolute configurations of 86 optically active - and -substituted ferrocenederivatives are known; all configurations have now been unambiguously correlated.

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Mit 2 Abbildungen

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9. Mitt. (34. Mitt. über Ferrocenderivate):G. Haller undK. Schlögl, Mh. Chem.98, 603 (1967).     

Synthese von 3-Hydroxy-1-oxo-4-alkyl-1H-benzo[d]pyrido[2,1—b]thiazolen

Zusammenfassung -[Benzothiazolyl-(2)]-acetessigsäurealkylester können zu Benzopyridothiazolen cyclisiert werden. Bei Umsetzung solcher substituierter Acetessigester mit Alkylhalogeniden in Gegenwart von Basen erfolgt Cyclisierung zu Benzopyridothiazolen, die an C-4 alkylsubstituiert sind. IR- und¹H-NMR-Daten dieser Heterocyclen und einiger ihrer Derivate werden mitgeteilt.

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Synthesis of 3-hydroxy-1-oxo-4-alkyl-1H-benzo[d]pyrido-[2.1—b]thiazoles

Ring closure of -[benzothiazolyl-(2)]-acetoacetates affords benzopyridothiazoles. In the reaction of these substituted acetoacetic acid esters with alkyl halides in the presence of bases, the formation of benzopyridothiazoles is observed; these heterocyclic compounds are alkyl-substituted at C-4. IR- and¹H-NMR-spectral data of the benzopyridothiazoles and some of their derivatives are given.

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Aus der DissertationN. Hawlitzky, Freiburg im Breisgau, 1970.     

Two-mode jahn-teller effect in nh+3

The two-mode E ? (? + ?) Jahn-Teller effect in NH⁺₃ is investigated theoretically. Using ab initio coupling constants, it is shown that the inclusion of the interaction between the degenerate stretching and bending vibrational modes is essential for understanding the experimental findings. An effective single-mode Jann-Teller hamiltonian is introduced to simulate the more complicated two-mode problem. Although such a hamiltonian cannot be expected to reproduce the details of the vibrational structure, it is generally found to reproduce the band shape of unresolved spectra most accurately.     

Erratum

Ohne Zusammenfassung

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Erratum

     

A self-silenced sound beam

Parametric loudspeakers are transmitting two high power ultrasound frequencies. During propagation through the air, nonlinear interaction creates a narrow sound beam at the difference frequency, similar to a light beam from a torch. In this work is added the physical phenomenon of propagation cancellation, leaving a limited region within which the sound can be heard—a 1 meter long cylinder with diameter 8 cm. It is equivalent to a torch which would only illuminate objects within 1 meter. The concept is demonstrated both in simulation and in experiment.     

Optical detection and ionization of donors in specific electronic and nuclear spin States

We resolve the remarkably sharp bound exciton transitions of highly enriched 28Si using a single-frequency laser and photoluminescence excitation spectroscopy, as well as photocurrent spectroscopy. Well-resolved doublets in the spectrum of the 31P donor reflect the hyperfine coupling of the electronic and nuclear donor spins. The optical detection of the nuclear spin state, and selective pumping and ionization of donors in specific electronic and nuclear spin states, suggests a number of new possibilities which could be useful for the realization of silicon-based quantum computers.     

Evidence for p-type doping of InN

The first evidence of successful p-type doping of InN is presented. It is shown that InN:Mg films consist of a p-type bulk region with a thin n-type inversion layer at the surface that prevents electrical contact to the bulk. Capacitance-voltage measurements indicate a net concentration of ionized acceptors below the -type surface. Irradiation with 2 MeV He+ ions is used to convert the bulk of InN:Mg from p to n-type, at which point photoluminescence is recovered. The conversion is well explained by a model assuming two parallel conducting layers (the surface and the bulk) in the films.