Research

Universität Hannover, Germany ;   UBC, Vancouver, Canada ;   JPL, Pasadena, CA, USA ;   Universität Köln, Germany.
    I am interested in the spectroscopic characterization of small, often very reactive molecules, particularly those of atmospheric or astrophysical and astrochemical interest. The spectroscopic techniques include rotational as well as low and high resolution infrared spectroscopy. And as a chemist, I am not afraid of synthesizing these molecules on a preparative scale or in situ. Throughout my scientific career, force field and quantum chemical calculations (ab initio, DFT) played an important role. Some more detail are in the following sections.

    Initially, I have studied mathematics and chemistry to become a teacher. During universitiy years, the emphasis was on mathematics, while it was on chemistry during the practical period in school.

    I began the studies to get my PhD in chemistry at the Universität Hannover, Germany, in 1988. I worked in the group of Prof. Helge Willner in the inorganic chemistry institute. The main objectives were the sythesis and characterization of chlorine oxides, preferrably those which may play a role in atmospheric chemistry and which were not known experimentally at that time. Using a halogen exchange reaction, I was able to obtain chloryl chloride, ClClO2 for the first time. The reaction proceeds schematically via
FClO2  +  XCl  __>  ClClO2  +  XF ;
where XCl can be, for example, AlCl3, BCl3, or HCl. ClClO2 was characterized by IR and UV/vis spectroscopy in neon and argon matrices and also in the gas phase. From the 35/37Cl and 16/18O isotopic shifts of n5 and n6 structural parameters of ClClO2 could be derived.
    It was impossible to synthesize the molecule on a preparative scale; thus, it has to be generated in situ. However, ClClO2 isolated in an argon matrix can be photo-isomerized to chlorine chlorite, ClOClO, and subsequently to dichlorine peroxide, ClOOCl. Both molecules were identified and characterized by IR spectroscopy.
Publications related to ClClO2.
    Other projects included the spectroscopic characterization of OClO and ClOO in a neon matrix, the preparation of covalent perchlorates XOClO3 (X = H, F, Cl) for an electron diffraction study, the preparation of FCl18O3 for a high resolution infrared study, and the participation in the spectroscopic characterization of CrF4 and CrF5.
Other publications related to work in Hannover.

    I moved to Vancouver, BC, Canada, in spring 1993 in order to work as a postdoc at the University of British Columbia. I worked in the group of Prof. Michael C. L. Gerry using microwave Fourier transform spectroscopy. The structural parameters of, e.g., SO2ClF and FClO3 have been determined. While six isotopomers of the former were studied in natural isotopic composition, a mixture of FCl16O218O and FCl16O3 was synthesized for the latter study. In all of the studies, the analysis and interpretation of the hyperfine structure was of great interest for me. Examples are the determination of the complete 35Cl quadrupole tensor for SOCl2, and the investigation of the unusual 19F paramagnetic shielding in BrF, IF, and SF2. The SF2 project was carried out together with Bethany Brupbacher-Gatehouse who is now at the Eidgenössische Technische Hochschule in Zürich, Switzerland.
Publications related to work in Vancouver.

    From spring 1995 to summer 1997 I obtained a stipend from the National Research Council to work at the Jet Propulsion Laboratory (JPL), Pasadena, CA, USA, as a NASA-NRC Resident Research Associate. While you may well know that JPL is heavily involved in NASA's unmanned space missions, it also an important place for Earth sciences, including atmospheric chemistry. I used submillimeter and millimeter spectroscopy to investigate molecules of atmospheric interest, often in collaboration with Dr. Edward A. Cohen. The first high resolution spectra of Br2O, OBrO, and ClClO2 have been obtained and analyzed. The spectroscopic constants were used to derive structural parameters and harmonic force constants and to gain insight into the halogen bonds from the hyperfine constants.
     Further projects were, e. g., the investigations of ClONO2 (chlorine nitrate) and OClO. For the latter molecule, an anharmonic (quartic) force field was derived in collaboration with G. Ole Sørensen. I also contributed to the JPL submillimeter, millimeter, and microwave catalog which contains line features for atmospheric chemists and radioastronomers.
Publications related to work in Pasadena.

     I have been at the I. Physikalische Institut of the Universität zu Köln, Germany in the group of Prof. Gisbert Winnewisser since summer 1997. The spectroscopic tools are similar to those used at JPL, however, the frequency range is extended even further. To a large extent, I am studying molecules of astrophysical and astrochemical interest, such as NH2 and various isotopomers of SO2 and H2CO (formaldehyde).
     In addition, I have continued to study halogen containing molecules, such as chlorosyl fluoride, FClO, chloryl fluoride, FClO2, and chlorine trifluoride, ClF3. For FClO, I have obtained the first high-resolution IR, microwave, millimeter and submillimeter spectra at the Universität/GH Wuppertal, Germany (Prof. Hans Bürger), at the Eidgenössische Technische Hochschule, Zürich, Switzerland (Prof. Alfred Bauder), at JPL, and in Köln, respectively. Furthermore, experimental structural parameters have been derived for the first time.
     Several recent projects involve vibration rotation interaction. They include for exaple ClClO2 with E. A. Cohen and D. Christen; FClO; FClO2 with J.-M. Flaud and H. Bürger; ethylene glycol with D. Christen and L. H. Coudert; and CH3CCH with P. Pracna.
     An additional project I am working on, is the Cologne Database for Molecular Spectroscopy which includes data related to work in Köln that might be of use for other spectroscopists, line predictions of atoms and molecules for radioastronomers, and some examples and hints to the SPFIT / SPCAT programs.
Publications related to work in Köln.