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Paul Scherrer Institut PSI Molecular Dynamics

Paul Scherrer Institut
5232 Villigen PSI, Schweiz/Switzerland
Tel. +41 56 310 21 11
Fax. +41 56 310 21 99

E-Mail: peter.radi@psi.ch

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Molecular Beam Apparatus

Polyatomic molecules and radicals are important species in combustion processes. But the investigation of their spectroscopy and dynamics in high temperature environments is often not feasible with conventional laser techniques due to congested spectra. Furthermore, the characterization of transition metal clusters is crucial in order to gain better insights into catalytic systems. The goal of the molecular beam facility at the PSI is to generate vibrationally and rotationally cold polyatomic molecules, (metallic) clusters, and radicals that are suitable for their spectroscopic investigation. We use an advanced non-linear technique in combination with more conventional methods for the measurement of these species in the controlled environment of the molecular beam.

The production of specific transient species in the molecular beam is achieved by laser-vaporization of metals and by pyrolytic, photolytic or discharge sources.


Molecular beam apparatus for multiplex spectroscopy. A molecular beam is generated by supersonic expansion through a pulsed valve which is mounted on an xyz-translation stage. For solid or liquid substances exhibiting a low vapor pressure, the source holder is resistively heatable in two stages by separate heating loops (thermocoax). For example, internally cold H2CO can be obtained by heating a sample of solid para-formaldehyde (≈ 360 K) to liberate the monomer which is co-expanded with He at backing pressures behind the valve of ≈ 1.5 atm. Transient species, like C3, are produced by applying a discharge assembly. Metal clusters are generated by laser vaporization in an home-built high-intensity source.