Spectroscopy of trapped ultracold complex molecular ions

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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.