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The characterization of tellurium selenide in its electronic ground state (X0 + ∑ − ) was possible by using LASER-ablation to isolate the diatomic in a pulsed molecular beam and by applying Fourier transform microwave spectroscopy to obtain the pure rotational spectrum. Employing a global multi-isotopologue analysis to transitions of 43 isotopologues of TeSe in seven vibrational states spectroscopic Dunham parameters Y l , m , Born–Oppenheimer breakdown coefficients δ l , m , the equilibrium bond lengths r e , as well as the vibration parameters ω e and ω e x e were obtained for all analysed isotopologues. For low vibrational states, the Morse-potential function describes the TeSe-potential very well and provides an estimate of the maximum dissociation energy for this semi-metal compound. In addition, the isotopologue independent molecular constants U l , m and the corresponding Born–Oppenheimer breakdown coefficients Δ l , m were determined. Quite large coefficients Δ 0 , 1 Te and Δ 0 , 1 Se were necessary for Watson's reference isotopologue independent analysis. This is rationalized by the interaction between the two sublevels of the electronic 3 Σ-state. Also the magnetic spin–rotation coupling constants that were achieved for some of the isotopologues reflect this electronic ground state. Field shift effects are found to be negligible.

The Fourier transform rotational spectra of the normal and the 13 C species of the 1:1 complex between difluoromethane and water have been measured. The rotational transitions are split into two component lines, due to the internal rotation of the water moiety. The barrier to this motion has been estimated to be 340(20) cm −1 . An improved structure of the complex has been obtained.

In this article, we present a setup for Stark-effect measurements using a Fourier transform-microwave (FTMW) spectrometer with coaxially oriented beam-resonator arrangement (COBRA). The open Fabry–Perot-type arrangement of spherical mirrors provides the possibility to mount the reflectors electrically insulated. Since no electrical surface currents of the resonator are inhibited, the propagation of the microwave field remains unaffected. If the microwave antennas and the valve are mounted at the same mirror, the other reflector can be set to a static high voltage potential. Together with a number of coaxially arranged circular electrodes a homogeneous field along the resonator axis can be achieved, allowing accurate Stark-effect measurements with COBRA-FTMW spectrometers. The arrangement is suitable even at low frequencies, where a parallel plate arrangement for Stark-effect measurement would increasingly interfere with the microwave field. The design of the coaxially aligned electrodes for Stark-effect a...

Zum diesjahrigen Fruhjahrssymposium der Jungchemiker kamen mehr als 200 Teilnehmer nach Dresden. Darunter waren neben Nachwuchschemikern aus Osteuropa Gaste aus den USA, die sich im Rahmen des Austauschs zwischen den Jungchemikern der North Eastern Section der ACS und der GDCh in Deutschland aufhielten.

The pure rotational spectra of 41 isotopic species of PbSe and PbTe have been measured in their X 1Sigma+ electronic state with a resonator pulsed-jet Fourier transform microwave spectrometer. The molecules were prepared by laser ablation of suitable target rods and stabilised in supersonic jets of noble gas. Global multi-isotopologue analyses yielded spectroscopic Dunham parameters Y01, Y11, Y21, Y31, Y02, and Y12 for both species, as well as effective Born-Oppenheimer breakdown (BOB) coefficients delta01 for Pb, Se and Te. Unusual large values of the BOB parameters for Pb have been rationalized in terms of finite nuclear size (field shift) effect. A direct fit of the same data sets to an appropriate radial Hamiltonian yielded analytic potential energy functions and BOB radial functions for the X 1Sigma+ electronic state of both PbSe and PbTe. Additionally, the magnetic hyperfine interactions produced by the uneven mass number A nuclei 207Pb, 77Se, 123Te, and 125Te were observed, yielding first determinations of the corresponding nuclear spin-rotation coupling constants.

The rotational spectrum of the molecular complex difluorodimethylsilane–argon has been investigated by pulsed jet absorption millimeter wave and pulsed supersonic jet Fourier transform microwave spectroscopy. The absolute energy minimum corresponds to a conformation with the argon atom lying in the F–Si–F plane of symmetry of difluorodimethylsilane. This is confirmed by the analysis of the observed splitting due to the internal rotation of two equivalent methyl groups. The V 3 barrier to the internal rotation of the two methyl groups has been determined to be 4.857(5) kJ/mol. The distance of Ar from the center of mass of difluorodimethylsilane is 4.07 A, with Ar–Si line forming an angle of 60.6° with the C–Si–C bisector. The zero point dissociation energy is estimated, from the centrifugal distortion constant D J , to be 2.75 kJ/mol.

Calcium or sodium atoms are added to selenium clusters in the reaction channel of a dual laser vaporization source to study the dependence of the product structures on the number and the valence of the metal atoms. Stabilities of product clusters are investigated by photofragmentation experiments. Several Ca M Se N clusters show special stabilities for compositions that can be related to bulklike cuboid structures, while no pattern of geometrical stabilities is found for Na M Se N clusters. Keeping a low sodium concentration in the reaction channel generates predominantly Na 2 Se N clusters. They are deposited in a nitrogen matrix and investigated by Raman spectroscopy. A low-frequency Raman band is found which is consistent with calculated frequencies of selenium chains terminated at each end by one sodium atom and bent into horseshoe shapes by an attractive interaction between the two sodium atoms. Structural models for the metal/selenium clusters are discussed which are based on the idea of an electron transfer from the metal atoms to the selenium clusters according to the metal valences.

The rotational spectrum of the molecular complex dimethylsilane– argon was investigated by free-jet absorption millimeterwave and molecular-beam Fourier transform spectroscopy. The absolute energy minimum corresponds to a conformation in which the argon atom lies in the plane of symmetry of dimethylsilane, perpendicular to the CSiC plane. The distance of Ar from the center of mass of dimethylsilane is 3.90 B, and the Ar atom is tilted 148 away from the Si atom. The zero-point dissociation energy was estimated from the centrifugal distortion constant DJ to be 2.2 kJmol1. Small splitting, due to tunneling of the Ar atom and internal rotation of the two methyl groups, was observed, measured, and used to determine the potential energy surface for these motions.

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