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Resolved Sideband Spectroscopy for the Detection of Weak Optical Transitions

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Doctoral thesis

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This thesis reports on the setup of a new ion trap apparatus designed for experiments with single 40Ca ions to perform molecular spectroscopy. The calcium ion is laser cooled, allowing for sympathetic cooling of the nonfluorescing molecular ion. The aim of these experiments is to explore loading and identifying molecular ions in RF-Paul traps, as well as developing new spectroscopic tools to measure transitions of molecular ions via the fluorescence of co-trapped 40Ca ions. Ground state cooling of a mixed ion pair is implemented as a first step towards increasing the sensitivity of our technique to the level necessary to measure transitions with low scattering rates like those present in molecular ions. Doppler cooling on the S12-P12 transition of the calcium ion results in the formation of a Coulomb crystal, the behavior of which may be used to infer properties of the molecular ion. Following cooling, sideband spectroscopy on the narrow S12-D52 quadrupole transition of calcium may be used to identify the mass of single molecular ions. This method is verified via a non-destructive measurement on 40CaH and 40Ca61O. The normal modes of the Coulomb crystal can also be used to extract information from the target ion to the control ion. By driving the blue side of a transition, laser induced heating can be put into the two ion system, which leads to changes in fluorescence of the 40Ca ion, first demonstrated with two Ca isotopes. Increasing the sensitivity of this technique requires ground state cooling of both the 40Ca ion and the ion of interest, enabling the transfer of the ions motional state into the ground state with high probability. This thesis demonstrates ground state cooling of the atomic ion and sympathetic cooling of a second ion 44Ca.

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  • Atomic and Molecular Physics and Spectroscopy

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