基于超冷分子高灵敏测量电子质子质量比变化的研究

Precise measurement of optical spectrum, absolute frequency and basic physical constants can be achieved with ultra-high accuracy and resolution based on the combination of femtosecond optical frequency comb and ultra-cold molecules. The ultracold atoms which are cooled with polarization gradient cooling method efficiently loaded into optical dipole trap by magnetic levitation technique. Feshbach resonance molecules in weakly bound states are prepared by controlling the interaction between atoms using Feshbach resonance. The controlled Raman adiabatic transfer channel from weakly bound Feshbach molecules to ground state ultracold molecules is constructed. The two lasers in stimulated Raman adiabatic transfer are simultaneously coherent locked using highly stable optical interferometry cavity. The controlled ultracold ground state molecules are produced. The absolute frequency difference between two lasers are precisely measured by optical frequency comb. Based on the theoretical model of Feshbach state bound energy and ground state hyperfine structure, the binding energy of ground state ultracold molecules with no magnetic is obtained. The energy levels information of the ground state molecules is obtained by changing the frequency of the two Raman laser. The variation of electron proton mass ratio is accurately measured with high precision potential curve data and the selection of optimal energy levels. These studies are of great significance to build a high-precision measurement system, explore new concepts and principles of precision measurement physics and develop more accurate measurement methods and techniques.

利用飞秒光学频率梳和超冷分子的实验结合，可以在最高精度和分辨率水平上实现精密光谱、绝对频率及基本物理常数的测量。本项目利用磁悬浮技术将偏振梯度冷却后的超冷原子高效装载在光学偶极阱中，利用Feshbach调控原子间相互作用，高效制备弱束缚态的Feshbach共振分子。构建弱束缚态Feshbach分子向基态超冷分子转移的受激拉曼绝热转移通道，利用高稳定光学腔对受激拉曼绝热转移的两束激光进行同步相干锁定，制备能级可控的超冷基态分子。采用光学频率梳精密测量两束激光绝对频率差，结合Feshbach态束缚能和基态超精细结构的理论模型获得基态超冷分子在零磁场下的束缚能。通过改变两束激光的频率，获取的基态分子的能级信息。利用高精度的势能曲线数据及选择最优化的能级，精密测量电子质子质量比变化。这些研究对于构建高精度的测量体系，探索精密测量物理新概念和新原理，发展更高精度的测量方法与技术具有重要意义。

项目执行期间，课题组建立了基于飞秒光学频率梳系统和超冷原子分子系统有机结合的研究平台，在此基础上开展了超冷分子和量子精密测量的相关研究工作，完成了项目的计划内容，获得了预期的研究成果。实验上首先将制备的超冷原子样品高效装载到交叉光学偶极阱中，利用高分辨双共振光学泵浦光谱技术测量了原子超精细相互作用常数。通过Feshbach共振精密调控光学偶极阱中超冷原子间相互作用，制备了弱束缚态的超冷分子。利用高稳定光学腔对受激拉曼绝热转移过程的两束激光实现了同步锁定，相干制备了振转能级可控的基态超冷分子，转移效率达到85%以上。利用飞秒光学频率梳输出不同频率的梳齿与受激拉曼绝热转移过程的两束激光拍频，获得了基态超冷分子在零磁场下的束缚能，相对不确定度小于10-9。实验精密调控两束拉曼激光的输出频率，获取了完整的基态超冷分子能级信息。通过超冷分子基单重态/基三重态和激发态能级构建Λ系统，利用不同电子态近简并的振转能级间隔变化测量了电子质子质量比变化，测量的相对误差小于10-16。本项目的相关研究为基于超冷原子分子的量子模拟、量子态操控和量子精密测量的研究提供了技术支持。