The production of ultracold molecules is one of the most exciting topics in the field of ultracold physics, which has important theoretical values and broad application prospects. We propose an ultracold atom-molecule conversion model in a closed-loop three-level system based on three available transitions, in which the population dynamics depends on three coupling fields and global phase. We investigate the atom-molecule conversion dynamics in the closed-loop three-level system. We show the distribution of population on excited molecular state and ground molecular state with arbitrary proportion can be achieved by adjusting pulse amplitudes of the external fields properly. We also explore the effects of time delay, pulse width and global phase on the conversion process. The results show that, by tuning these parameters, the stable atom-molecule conversion with arbitrary proportion can be realized.

超冷分子的制备是超冷物理领域最令人兴奋的课题之一，具有重要的理论价值和广阔的应用前景。我们提出了一个基于三个可用跃迁的闭环三级系统中的超冷原子-分子转换模型，其中种群动态取决于三个耦合场和全局相位。我们研究了闭环三级系统中的原子-分子转换动力学。我们表明，通过适当调整外场的脉冲幅度，可以实现任意比例的激发态分子态和基态分子态的种群分布。我们还探讨了时间延迟、脉冲宽度和全局相位对转换过程的影响。结果表明，通过调整这些参数，