非极性碘分子Rydberg-Stark减速和俘获

Cold substance is currently a hot research topic. The technology for cooling atom is very mature. Scientists around the world are exploring effectively cooling molecules. The temperature of cold molecules prepared by photo-association can reach micro-K magnitude, but usually it is only applicable to weakly bound, easy dissociation of alkali metal molecules. Multistage Stark deceleration has been widely used, but only applicable to polar molecules. Optical cooling is just applicable to a small number of specific molecules, which has simple structure and specific energy-level system. For nonpolar molecules, the desirable cooling method is Rydberg-Stark deceleration. At present, this technology has been successfully applied to the cooling of hydrogen molecules.. In this project we intend to use Rydberg-Stark technology to decelerate and trap molecular iodine. In nature there is only one stable isotope of iodine, and iodine molecular spectroscopy is often used for wavelength calibration. Ultracold molecular iodine in the area of hyperfine spectroscopy has broad application prospects. In the weak field we first excite iodine molecules to the appropriate Rydberg states, which has a huge electric dipole moment, then a Stark deceleration field is applied to cooling the molecules. After that the molecules are trapped in the electrostatic trap. The temperature, density, life time, and so on cold molecular parameters will be measured by field ionization time of flight mass spectrometry. There is no report about cooling molecular iodine.

冷物质是目前研究热点课题，原子冷却技术已非常成熟，人们正在探索有效冷却分子的方法。光缔合制备的冷分子温度可以达微K量级，但通常只适用于弱束缚、易离解的碱金属分子；多级Stark冷却获得了较多应用，但只适用于极性分子；光学冷却适用于结构简单、能级特殊的少数分子。对于非极性分子较理想的冷却方法是Rydberg-Stark减速，这种方法目前已成功应用于氢分子冷却。. 本项目拟采用Rydberg-Stark减速技术对碘分子进行冷却。碘在自然界只有一种稳定的同位素，碘分子光谱常常用于波长标定，超冷碘分子在超精细光谱学方面有广泛应用前景。本项目先把弱场中的碘分子激发到合适的Rydberg态，使其拥有巨大电偶极矩，然后经过一级Stark减速实现冷却，进而俘获在静电阱中。采用场电离飞行时间质谱测量冷分子的温度、密度、寿命等参数。目前还未见冷却碘分子的报道。

建立了分子Rydberg-Stark减速和冷却实验装置，编写了控制整体系统运行的程序，实现了实验数据自动化采集。由于难以克服对重原子和分子减速需要大的电场梯度和真空电极之间易于放电的矛盾，导致实验工作未能实现碘分子的Rydberg-Stark减速。鉴于许多分子的激发态能量和精确的绝热电离能仍然未知，在我们已具备的实验条件下，开展了多原子分子里德堡态的脉冲场电离（质量分辨阈值电离）实验研究，首次测量了许多分子的精确的激发能、绝热电离能和Rydberg态的能级信息。配合密度泛函理论计算和Franck-Condon光谱模拟分析并指认了实验观察到的光谱对应的振动模式。分析了各种取代基对跃迁能和电离能的影响，为相关分子的科学研究和工业生产提供了重要参考资料。. 对于许多多原子分子，由于取代基的相对取向不同导致分子存在异构物。虽然不同的异构物具有相同的质量，但能量和光谱互不相同。异构物的光谱可以通过测量电离能、转动惯量等参数进行分辨。但对于较弱的光谱，很难通过这两种方法毫不含糊地分辨异构物光谱。烧孔光谱是直接分辨异构物光谱的较理想和高效率的方法，我们经过反复尝试，掌握了烧孔光谱的实验技术和方法，对许多分子进行了研究，获得了很好的信噪比和较高的分辨率，为开展复杂分子的研究打下了基础。...