Spectroscopy and dynamics of cold and ultracold molecules

近十年来，受超冷原子领域突破的启发，冷分子研究发展迅速。由于明显的量子效应出现在低温下的热平均中，冷分子的行为预计与高温下的分子大不相同。分子具有许多原子所不具备的特殊特征，如旋转和振动运动、更远距离的多极相互作用和更丰富的化学反应。因此，冷分子的集合是化学和物理学新领域的宝库；通过其他方式完全无法获得。由于即使在1k下也很难制造分子，所以我在过去五年的研究主要集中在开发新的实验技术来制造冷分子。最近，我们在世界上首次成功地用磁阱捕获了冷多原子自由基。基于我们已经建立的技术和新的原创思想，我们将继续在冷分子的前沿研究，旨在在这一新兴领域取得重大突破。

Cold molecule research has grown rapidly in the last ten years, inspired by the breakthroughs in the field of ultra cold atoms. Since pronounced quantum effects emerge from thermal averages at low temperatures, cold molecules are expected to behave quite differently from those at high temperatures. Molecules have many special features that atoms do not have, i.e. rotational and vibrational motions, longer range multipole interactions, and richer chemical reactivities. Ensembles of cold molecules are therefore a treasury of new frontiers in both chemistry and physics; completely unavailable by any other means. Since it is still difficult to create molecules even at 1 K, my research in the last five years has mainly focused on developing new experimental techniques to create cold molecules. Very recently we have succeeded in trapping cold polyatomic free radicals in a magnetic trap for the first time in the world. Based on the techniques we have established and new original ideas, we will continue on the cutting edge research on cold molecules, aiming to achieve major breakthroughs in this newly emerging field. My project in the next five years will consist of five topics: 1) Development of techniques to make ultracold molecules below 1 mK, 2) Detailed study of cold collisions and reactions, 3) Ultra-high resolution spectroscopy of cold molecules, 4) Coherent control of cold molecules by laser fields, and 5) Spectroscopy and dynamics of cold molecules in quantum condensed phases. Through these studies, new phenomena intrinsic to cold molecules will be investigated, such as quantum tunneling effects and the wave nature of molecules. Experiments on cold collisions and reactive scattering would take us into a strange new world in chemistry, namely ultracold chemistry, which may be relevant to interstellar chemistry. Coherent control such as the enantiomeric purification of racemic mixtures by laser fields is an important application of cold molecules to be tackled, which would make an impact in analytical and pharmaceutical science. Other applications include the observation of small energy differences in chiral molecules, and the development of quantum simulators/computers. The former would contribute to the understanding of the origin of life, and the latter to the material and information sciences. Furthermore, we will challenge the creation of a molecular Bose-Einstein condensate, a new phase of the molecular matter wave which has never been observed. Studies of cold molecules open unlimited possibilities, in terms of not only basic natural sciences, but also practical applications contributing to the broad scientific community, which offer a completely new field of research in physics and chemistry.