Generation and manipulation of ultra-cold molecules by coherent photoassociation

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Cold molecules were produced by buffer gas cooling and selected by Stark velocity filter.At first stage, He buffer gas in the collision cell at the temperature of liquid nitrogen was prepared for cooling the target molecules by thermal collision. The target gas after the collision cell was transferred to high vacuum chamber to detect time of flight spectrum. The molecule was distinguished by mass spectrometer from the buffer gas. From the observed time of flight spectrum we could see the effective cooling of the molecule which was introduced at the room temperature. In the case of acetaldehyde, molecular beam of 130K was obtained.In the next stage, slow moving molecules in the thermal Maxwel-Bolzmann distribution were selected by quadra-pole electric field. High-voltage of 200kV/cm was applied to the 1mm gap of the electrodes. As a result, the lower filed seeking states of the ND_3 molecule were successfully selected with the velocity corresponding temperature of 8 K. The higher field seeking states were also selected by the wire electrode for the first time.And finally, laser cooling technique was also reinvestigated in order to apply for molecular system in the future. Rb atom was trapped by magneto optical trap at the temperature of micro K By these studies, the way to ultra cold molecules is developed. It would be significant because the way is applicable to general molecules with permanent dipole moment