Laser spectroscopy of molecules

我们最近已经实现了分子的可靠生产，平移温度在毫开尔文水平。这种超冷分子最有前途的应用之一是高分辨率激光光谱学。据我们所知，在这个项目中，我们将进行这种类型的第一次实验。特别是，我们将展示HD+分子振动跃迁的激光光谱，集中在波长为1.4(m)的泛音跃迁上。HD+分子非常重要，因为它是最简单的分子之一，只包含一个电子。振动跃迁频率的精确测量最终将允许(1)测试分子水平精确计算的理论方法；（ii）证明分子中存在QED效应；（iii）以一种新颖的方法确定电子与质子的质量比，并且可能比其他方法具有更高的精度；（iv）测量核性质，如四极矩，(v)测试核质量比的时间独立性。两年的目标包括实现10-8级的光谱分辨率，这样就可以分辨超精细结构的总体特征，并以类似的精度获得一些旋转-振动过渡频率的绝对测量。这将通过飞秒频率梳来实现。为了确定其准确性，将对系统效应进行调查。在我们的项目中开发的方法也将适用于各种其他分子离子。

We have recently achieved reliable production of molecules with translational temperatures at the millikelvin level. One of the most promising applications for such ultracold molecules is high-resolution laser spectroscopy. In this project we will perform what will be, to our knowledge, the first experiment of this type. In particular, we will demonstrate laser spectroscopy of vibrational transitions in the HD+ molecule, concentrating on an overtone transition at a wavelength of 1.4(m . The HD+ molecule is of fundamental importance because it is one of the simplest molecules, containing just a single electron. Precise measurement of vibrational transition frequencies will ultimately allow (i) to test theoretical methods of precision calculation of molecular levels; (ii) to demonstrate the existence of QED effects in molecules; (iii) to determine the ratio of electron-to-proton mass in a novel way and with potentially higher precision than with alternative methods; (iv) to measure nuclear properties such as quadrupole moments, (v) to test the time-independence of nuclear mass ratios. The two-year goal consists in achieving a spectral resolution at a level of 10-8 such that the gross features of the hyperfine structure can be resolved, and in obtaining an absolute measurement of a few rotational-vibrational transition frequencies with a similar precision. This will be performed by means of a femtosecond frequency comb. An investigation of systematic effects will be performed in order to establish the accuracy. The methods developed in our project will also be applicable to a large variety of other molecular ions.