<p> Trapped ions can be isolated from external perturbations such as collisions with other atoms or electric and magnetic field inhomogeneities. For this reason, trapped ions can be useful in spectral measurements, quantum information technology and studying quantum behaviour. In this thesis, I discuss a trapped-Mg+ apparatus for studying the quantum mechanics of atoms. I describe the laser interactions that allow us to coherently excite our atoms. I go on to discuss the actual apparatus for trapping ions and making precise measurements, the hyperfine structure of 25 Mg+ and a proposed linewidth measurement. </p> / Thesis / Master of Science (MSc)