Trapping of Molecules through Stark Effect

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The techniques of conventional laser cooling and trapping are not effective for molecules because the interaction between electromagnetic fields and molecules are usually very weak. The goal of this research project is to develop a 3-dimensional trapping for molecules by use of static electric fields or strong laser radiation. Outcomes of our research are summarized as follows.1. We theoretically investigated dynamics of linear polar molecules in static quadrupole electric fields and their collision process. Classical analysis shows that molecules rotating in a specific direction experience a restoring force toward the center of the field distribution, being 3-dimensionally trapped. The trapping lifetime was formulated in terms of the Majorana transition. We also proposed a method of decelerating molecules with a ring electrode.2. The optical dipole force was used to trap small crystals precipitated from saturated solution. It has been demonstrated that the mechanical force influences dynamics of crystal growth in supersaturated alum solution and produces spherical polycrystals. Precipitated crystals are spatially distributed by their size because of the difference in the gradient force acting on them.3. Laser ablation of molecular crystal was carried out to produce gaseous molecules inside a far-off-resonant optical dipole force trap. Our method is unique in that the trapping laser also works as an ablation light source. The laser ionization and detection of molecules trapped in the focus of CO_2 laser beam are now in progress.