THEORETICAL CHEMISTRY: MOLECULAR SPECTROSCOPY AND DYNAMICS 263 CHIMIA 2004, 58, No. 5 Chimia 58 (2004) 263–275 © Schweizerische Chemische Gesellschaft ISSN 0009–4293 EDITORIAL AND REVIEW Theoretical Chemistry: Molecular Spectroscopy and Dynamics 39th Symposium on Theoretical Chemistry 2003 (STC 2003) 28 September to 2 October 2003, Gwatt, Lake Thun, Switzerland# Fabio Mariottia, Martin Quacka*, Martin Willekea, and Jürgen Stohnerb Abstract: We provide a short review of the scientific meeting defined by the title of this article, which may at the same time serve as a compact review of the field with a substantial number of references to recent work. Exciting new developments in experiments on high-resolution molecular spectra and their analysis as well as new theoret- ical developments in the calculations of such spectra and the related time-independent and time-dependent quan- tum dynamics of molecules have led to new answers but also to new questions in the fields of molecular kinetics, molecular reaction dynamics, molecular chaos and statistical mechanics as well as fundamental symmetries in mo- lecular processes. Particular stress is placed on fundamental aspects and new directions. Keywords: Chemical reaction kinetics · Molecular dynamics · Molecular spectroscopy · Quantum chemistry · Theoretical chemistry Introduction Arbeitsgemeinschaft Theoretische Chemie (AGTC) of the Deutsche Bunsenge- The present Special Issue of CHIMIA is sellschaft (DBG), the Deutsche Physikali- devoted to the scientific subject as men- sche Gesellschaft (DPG), and the Ge- tioned in the title of this review and which sellschaft Deutscher Chemiker (GDCh). was also the topic of a scientific meeting in About 170 participants attended the sympo- Gwatt, on the shore of Lake Thun in the fall sium which offered 28 lectures of 45 min of 2003. The 39th Symposium on Theoret- each and two poster sessions with a total of ical Chemistry (STC 2003) was the latest in about 125 posters. The main theme of the an annual series of meetings with a long tra- meeting STC 2003 is at the heart of the in- dition in Europe and in Switzerland. In- teractions of experiment and theory in deed, it was the tenth time that the meeting chemistry, as the location was in the heart returned to Switzerland with the following of Switzerland, near the capital and the previous times, locations, and chairmen: Bernese mountains (indeed, the Abstract *Correspondence: Prof. M. Quack aPhysical Chemistry 1966 Zürich (Heinrich Labhart), 1969 Book included some basic history of ETH Zürich (Hönggerberg) Spiez (Georges Wagnière), 1972 Genève Switzerland [1]). Molecular Spectroscopy CH-8093 Zürich (Laurens Jansen), 1976 Basel (Martin Jun- has always had a special relation to Theo- Tel.: +41 1 632 44 21 gen), 1980 Wildhaus (Klaus Müller), 1984 retical Chemistry, and the theme of the Fax: +41 1 632 10 21 E-Mail: [email protected] Emmetten (Ulrich Müller-Herold), 1988 meeting follows an earlier one about a http://www.ir.ethz.ch/ Pontresina (Karl Lendi), 1994 Fiesch decade ago [2]. In the present short review bInst. of Chemistry and Biological Chemistry (Hanspeter Huber), 1998 Gwatt (Walter we introduce this special issue of CHIMIA ZHW Winterthur CH 8401-Winterthur Thiel). This time, the meeting was organ- by summarizing the lectures and some of ized by Hans-Peter Lüthi and Martin Quack the discussions of the meeting with fairly # A Symposium under the Auspices of the Division from the Swiss Federal Institute of Technol- extensive references, and thus this may al- Chemical Research of the Swiss Chemical Society ogy (ETH) Zürich and Jürgen Stohner from so serve as a very compact review of the (SCS) and the Arbeitsgemeinschaft Theoretische Chemie (DBG, DPG, GDCh) with Conference Chairmen the Zürich University of Applied Sciences current status of at least part of the field. Hans Peter Lüthi and Martin Quack (ETH Zürich) and Winterthur (ZHW) under the Auspices of This is then complemented by a small se- Jürgen Stohner (Zürich University of Applied Sciences the Division Chemical Research (DCR) of lection of papers from some of the invited Winterthur) the Swiss Chemical Society (SCS) and the speakers. It was not possible here to include THEORETICAL CHEMISTRY: MOLECULAR SPECTROSCOPY AND DYNAMICS 264 CHIMIA 2004, 58, No. 5 more for reasons of space and cost, but we C8H10), permanent dipole and quadrupole Session 2 hope that our review provides at least some potentials, and adiabatic channels including insight into those aspects not represented in centrifugal potentials. Jürgen Troe dis- This session chaired by Werner Kutzel- the following papers. These include at least cussed also certain reactions of great im- nigg, University of Bochum (Fig. 3) start- contributions from several groups at Swiss portance for the chemistry of the atmos- ed on Monday with a talk given by Wim universities as well as one from Germany phere such as H + O2 (and isotopomeric Klopper, University of Karlsruhe (Fig. 4) and two from France. Given the theme of versions with D, T, Mu) and OH + OH. In on ‘Explicitly-Correlated Calculations of the meeting, there is an exceptional propor- the latter case, a global analytical potential Excitation Energies’. The background of tion of experimental work presented in such energy hypersurface exists [10], and the these techniques, which owe much to the a theoretical meeting, which led to many speaker pointed to the need for such poten- chairman and the speaker himself in this stimulating interactions. tial energy hypersurfaces for dynamical session, was lucidly introduced. Explicit- calculations. Beyond the technical aspects, ly-correlated coupled cluster calculations he also provided the audience with a lively up to triple excitations are almost routine Session 1 journey through time and history, mention- in high-quality ab initio studies of poten- ing his early associations with the follow- tial energy hypersurfaces, energetic and After a short welcome by the organizers ing speaker (Martin Jungen), the chairman spectroscopic quantities for molecules and the chairman (Martin Quack) of Ses- and some of the older members in the audi- with less than six atoms [12]. The compu- sion 1, the meeting started already Sunday ence, such as Tino Gäumann, who had not tational accuracy reached demands to con- evening with an opening lecture by Jürgen missed the opportunity to join this event. sider various corrections (e.g. relativistic Troe, University of Göttingen (Fig. 1) on Martin Jungen, University of Basel spin-orbit and non Born-Oppenheimer ‘Reaction Dynamics with Wavepackets, (Fig. 2) talked on ‘What is a Muon Doing in corrections). Very large one-electron basis Adiabatic Channels, and Classical Trajec- Atoms or Molecules?’. The muon µ is an el- sets are needed (with high orbital angular tories’. Whereas quantum scattering calcu- ementary particle belonging to the Lepton lations of inelastic collisions are most accu- family. Its mass is about 207 times the mass rate, the numerical effort is prohibitive for of the electron or about 11% of the atomic larger systems involving many atoms. Cap- mass unit (≈0.11 u). It has a mean lifetime ture rate constants dominate chemical ki- of about 2.2×10–6 s. It decays into an elec- netics of barrierless reactions and statistical tron or positron plus neutrinos and exists as theories, such as the statistical adiabatic particle and anti-particle (µ+ and µ–). µ+ can channel model, have proven useful in this be considered as a light proton, whereas µ– context [3–5]. It has been demonstrated re- could be termed a heavy electron. (µ+e–) cently that the combination of classical tra- can be considered a light isotope of hydro- jectory calculations (with full quantum gen (Muonium, Mu). In a theoretical study, treatment of the capture) with adiabatic ‘exotic’ molecules have been investigated channel calculations describe capture rate which include one µ– particle: (ppµ–)+ + constants even down to very low tempera- (which would correspond to H2 ), – – 2+ 2+ tures (milli Kelvin) where quantum effects (ααµ e ) (corresponding to He2 ). Mar- are expected to be most prominent [6–9]. tin Jungen discussed various aspects of Ingredients for the calculation of capture bonding in these exotic systems as well as rate constants are potential energy surfaces, the role of the Born-Oppenheimer approxi- including for example ion-dipole interac- mation [11]. He also mentioned the potential + + + – + tions for charged reactants (e.g. O2 + importance of (p p µ ) for myonic fusion. Fig. 3. Werner Kutzelnigg, Bochum Fig. 1. Jürgen Troe, Göttingen, explaining Fig. 2. Martin Jungen, Basel, with a picture of Fig. 4. Wim Klopper, Karlsruhe, in his clear reactions lively with both hands, starting to Robert Mulliken in the background, from and highly instructive lecture make a high flight in his lecture whose famous lecture the title of Martin Jungen’s lecture was adapted THEORETICAL CHEMISTRY: MOLECULAR SPECTROSCOPY AND DYNAMICS 265 CHIMIA 2004, 58, No. 5 momentum quantum number l) which are has been used to obtain the OH overtone lows to identify carbon chains through costly or even computationally prohibi- spectrum up to six quanta of OH-stretching their electronic absorption spectrum. The tive, simplified treatments are strongly excitation (about 22000 cm–1) for the two sta- odd chains are more reactive and short- needed to treat even larger molecules. ble HONO isomers. Numerous perturbations lived and are investigated by mass-selec- CC2(R12) and CCSD(R12) are suitable have been identified and analyzed. In combi- tive resonant two-photon ionization tech- methods for larger molecules [13]. The nation with band intensities and intensity dis- niques (R2C2PI, [21]). Understanding the R12 method describes the Coulomb hole tributions this allows a thorough understand- electronic spectra poses a challenge to the- and the electron-cusp correctly by intro- ing of intramolecular dynamics up to very ory since one would require line positions ducing as a scaling factor the inter-elec- high vibrational excitations well into the vis- to better than 1 cm–1 for the carbon chain tron distance.