Laser Centre Vrije Universiteit, de Boelelaan 1081, NL-1081 HV Amsterdam, The Netherlands.
Faraday Discuss. 2009;142:25-36; discussion 93-111. doi: 10.1039/b819099b.
The recently demonstrated methods to cool and manipulate neutral molecules offer new possibilities for precision tests of fundamental physics theories. We here discuss the possibility of testing the time-invariance of fundamental constants using near degeneracies between rotational levels in the fine structure ladders of molecular radicals. We show that such a degeneracy occurs between the J = 6, Q2 1 and the J = 8, Q = 0 levels of the various natural isotopomers of carbon monoxide in its a 3pi state. As a result, the 2-photon transition that connects these states is 300 times more sensitive to a variation of m(p)/m(e) than a pure rotational transition. We present a molecular beam apparatus that might be used to measure these transitions with a fractional accuracy of 10(-12). Ultimately, the precision of an experiment on metastable CO will be limited by the lifetime of the a 3pi state. We will discuss other possible molecules that have a suitable level structure and can be cooled using one of the existing methods.
最近展示的冷却和操纵中性分子的方法为基础物理理论的精密测试提供了新的可能性。在这里，我们讨论了使用分子自由基精细结构梯级中的旋转能级之间的近简并来测试基本常数的时间不变性的可能性。我们表明，在其 a 3pi 态的各种天然同位素的一氧化碳中，J = 6，Q2 1 和 J = 8，Q = 0 能级之间存在这种简并。因此，连接这些状态的 2 光子跃迁对 m(p)/m(e)的变化的灵敏度比纯旋转跃迁高 300 倍。我们提出了一种分子束装置，该装置可以用于以 10(-12)的分数精度测量这些跃迁。最终，CO 的亚稳态实验的精度将受到 a 3pi 态寿命的限制。我们将讨论其他具有合适能级结构且可以使用现有方法之一冷却的可能分子。
