一、引言随着自然科学的发展,特别是量子物理学的发展,出现了一门崭新的学科——微波波谱学。人们发现,某些粒子(原子或分子)具有简单的微波波谱,其超精细能级之间的跃迁频率(微波频带)受自然因素和外界环境的影响比较小。就考虑能不能利用这种特性作为频率与时间的基准。 1945年美国物理学家哥仑比亚大学的LRabi教授建议利用铯束磁共振的方法,建立原子频率和时间标准。四年之后,美国国家标准局(NBS)首先建立利用氨J=3,K=3吸收线稳定晶振的原子钟。到1952年,世界上第 I. INTRODUCTION With the development of natural sciences, especially the development of quantum physics, a brand new discipline has emerged - microwave spectroscopy. It has been found that some particles (atoms or molecules) have a simple microwave spectrum whose transition frequency (microwave frequency band) between hyperfine levels is less affected by natural factors and the external environment. Consider whether you can use this feature as a benchmark for frequency and time. In 1945, Professor LRabi of Columbia University, an American physicist, proposed using cesium beam magnetic resonance method to establish atomic frequency and time standard. Four years later, the National Bureau of Standards (NBS) first established an atomic clock that stabilizes the crystal using an absorption line of ammonia, J = 3, K = 3. By 1952, the world’s first