Spectroscopy of trapped ultracold complex molecular ions

这个项目的目的是首次展示在超低动能和几乎没有碰撞的情况下复杂分子离子的激光光谱。最近，我们证明了将复杂分子离子(含有数十个原子)的外部自由度冷却到接近100MK的温度是可能的。所采用的方法是在射频离子陷阱中用激光冷却原子离子进行共振冷却。在这种条件下，分子离子被嵌入有序结构(库仑晶体)中，在那里它们可以储存几分钟到几个小时。UVH环境提供了几乎没有碰撞的情况，首次实现了对弱速率过程的研究。作为一个目标，我们试图确定几个物种在极低强度和连续波照射下的光碎裂率，即在线性方案中。第二个目标是展示振动光谱。振动激发的检测不能通过荧光来执行，而必须间接地检测。为此，将探索三种不同的技术。为了扩大光谱种类的范围，我们将在两种新的模式下研究交感冷却的可行性：(I)非常大的、高度带电的(质子化)蛋白质，例如细胞色素-C和去肌红蛋白分子(质量分别为13000 Amu和17.000 Amu)，以及(Ii)含有过渡金属原子的有机金属络合物，例如氧镍络合物。后者对寻找分子中的宇称破坏(PV)效应很感兴趣。

The aim of this project is to demonstrate, for the first time to our knowledge, laser spectroscopy of complex molecular ions in the regime of ultralow kinetic energy and in a near-absence of collisions.Very recently, we have demonstrated that it is possible to cool the external degrees of freedom of complex molecular ions (with tens of atoms) to temperatures near 100 mK. The employed method is sympathetic cooling by laser-cooled atomic ions in a radiofrequency ion trap. Under such conditions, the molecular ions are embedded in ordered structures (Coulomb crystals), where they can be stored for several minutes up to hours. The UVH environment provides near-absence of collisions, enabling, for the first time, the study of processes with weak rates. As one goal, we seek to determine the photofragmentation rates of several species at very low intensities and continuous-wave irradiation, i.e. in the linear regime.A second goal is the demonstration of vibrational spectroscopy. The detection of a vibrational excitation cannot be performed via fluorescence, but has to be detected indirectly. Three different techniques will be explored to this end. An appropriate test molecule is protonated tyrosine.In order to enlarge the range of species that can be spectroscopied, we will investigate the feasibility of sympathetic cooling in two new regimes: (i) very large, highly-charged (protonated) proteins, such as, e.g. Cytochrome-C and Apomyoglobin molecules (mass (13000 amu and (17.000 amu, respectively), and (II) organometallic complexes containing transition metal atoms, e.g. oxorhenium complexes. The latter are of interest for the search for parity violating (PV) effects in molecules.