Mainz 1997 – wissenschaftliches Programm

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A: Atomphysik

A 11: Poster II

A 11.14: Poster

Dienstag, 4. März 1997, 18:00–20:00, Poster II

Broadening and shift of ion motional frequency response induced by spatial dissymmetries in a Paul trap — •Nicolas Papageorgiou, Joëlle Rocher, Michel Vedel, and Fernande Vedel — Université de Provence, PI2M (URA 773), Case C21, F-13397 Marseille Cedex 20

Quadrupole ion traps are actually used for fundamental and industrial research. High resolution laser spectroscopy, metrologyand high resolution mass spectrometry are three major applications of the trap. In a mathematically pure quadrupole ion trap the equations of ion motion are linear with space in all three directions. eal traps however have geometrical defects. The ”pure” quadrupole trapping field is ”contaminated” by higher multipoles of all orders and ion motion equations become non linear. As a result experimental measurements on the trapped ions can be eventually limited in resolution. On the other hand non-linearities in ion motion and the possibility to observe one or many ions for long time are useful for studying non-linear dynamic behavior of isolated micro- or meso-systems. The ion motion can be excited in a resonant way. We have studied the absorption of motional energy by a technique of resonant ejection and report results on the lineshape, shift and width of the absorption signals. These characteristics give quantitative and qualitative informations about the real ion trap geometry. Furthermore we report frequency broadening and shift of the absorption lineshape which is not induced by collisions but is due to spatial dissymetries.