Laser techniques for vibrational excitation have been improved. Tunability has reached 1 GHz around each carbon dioxide laser line, stability is better than 0.1 MHz over long periods, laser power is up to 25 W, computer control has been implemented for data handling, for linearisation of tuned frequency intervals and for generation of coherent multicolour laser interaction zones. It is now possible to study chemical reactions with rotationally selected molecules in high vibrational states, with excitation levels of up to 5000 per cm.
Analysis of reactive scattering data has determined a threshold energy of about 0.5 eV for the onset of the reaction sodium plus sulphur hexafluoride to sodium fluoride plus sulphur pentafluoride. A strong influence of vibrational excitation on the reaction probability was found.
Vibrationally excited sulphur hexafluoride molecules were used in scattering experiments to characterize a gallium selenide (001) surface. The azimuth angle was determined from helium atom diffraction measurements. The gallium selenide surface had an anisotropically corrugated nature.
Chemical reactions between vibrationally highly and efficiently excited molecules became possible due to recent developments (Nijmegen) connected to multiphoton excitation of polyatomics. This improved technique shall be applied to a simple system, of which considerable knowledge has been built up in recent years.
The scattering machine (Gottingen) allows differential cross section measurements. Being equipped with a laser for electronic excitation of the atomic beam the influence of this type of excitation can be studied at the same time. Additional options for single photon excitation of the molecule will be applied. Combining the
Nijmegen-Gottingen expertise promises new results in a virgin-field of research.
Funding SchemeCSC - Cost-sharing contracts