High resolution microwave spectroscopy

这项研究利用气体分子的旋转速度来确定它们的几何形状。使用的方法类似于敲钟，拍子敲击钟，钟就会以其形状、大小和组成特征的音调（频率）响起。在我们的研究中，拍子被微波脉冲取代，这给分子带来了额外的能量。当分子失去这种能量时，它们发射的微波辐射的特征频率也由它们的形状、大小和组成决定。我们用频率的模式（频谱）来确定分子的几何形状。此外，我们可以如此精确地测量频率，以至于我们可以（并且确实）使用基本模式的微小变化来确定分子的柔韧性，以及获得分子中电子（将分子粘合在一起的胶水）如何排列的信息。我们正在研究含金属的小分子。它们是通过用激光汽化固体金属，并允许蒸汽与含有惰性气体（例如氩气）的另一种物质反应来制备的。然后将得到的混合物作为射流注入抽真空的细胞中。这个过程使分子保持足够长的时间，以便对它们进行研究。我们正在研究的一些特殊化合物中，惰性气体与金属的结合非常强烈，这种结合可以被认为是化学结合！在其他工作中，我们评估了一些非常精确的参数，特别是键长，在物理上有多大的意义。

This research uses the speeds of rotation of gaseous molecules to determine their geometries.  The method used is analogous to ringing a bell, in which a clapper hits the bell, which then rings at tones (frequencies) characteristic of its shape, size and composition.  In our research the clapper is replaced by a pulse of microwaves which gives the molecules extra energy.  As the molecules lose this energy they emit microwave radiation at characteristic frequencies dictated also by their shape, size and composition.  We use the patterns of the frequencies (the spectrum) to determine the molecular geometries.  Furthermore, we can measure the frequencies so precisely that we can (and do) use small variations from the basic patterns to determine how flexible the molecules are, as well as to obtain information on how the electrons in the molecules (the glue holding the molecule together) are arranged. We are studying small molecules containing metals.  They are prepared by vaporizing solid metal with a laser, and allowing the vapour to react with another substance contained in a noble gas (e.g. argon).  The resulting mixture is then injected as a jet into an evacuated cell.  This procedure holds the molecules long enough for them to be studied. Some specific compounds we are studying are those in which noble gases attach themselves to metals so strongly that the bonding can be considered chemical bonding!  In other work we assess how meaningful physically some of our very precise parameters, particularly bond lengths, really are.