Techniques for achieving complete quantum control over atoms have been developed and perfected over the past four decades with great success. This work has led to multiple Nobel prizes and has been the catalyst for rapid advances in a broad array of research fields. A natural progression forward is to develop control over molecules. Compared to atoms, molecules have an increased complexity in their internal structure due to their additional degrees of freedom of rotations and vibrations. Control over these additional degrees of freedom would allow for the study of chemistry with unprecedented detail, the study of new many-body effects, and more precise tests of fundamental physics. The work in this thesis represents a step forward in the goal of having complete quantum control over a molecule. We demonstrate rotational cooling on the silicon monoxide cation (SiO$^+$) via optical pumping with a spectrally pulse-shaped broadband laser. Cooling is achieved on a 100 ms time scale and attains a ground state population of 94(3)\% ($T=0.53(6)$ K). I also describe a novel approach to pulse shaping for populating arbitrary rovibrational states of molecules with diagonal Franck-Condon Factors (FCFs). This technique is demonstrated on SiO$^+$ and is used to achieve steady state preparation of so-called molecular super-rotors. We demonstrate a narrow rotational population distribution ($\Delta N=3$) around arbitrary targeted rotational states between $N=0$ and $N=65$. Control is accomplished through asymmetric pumping of transitions that add and remove angular momentum such that population is stochastically driven into a target rotational state. Furthermore, preliminary results demonstrating selective population of the first excited vibrational state are also presented. The full preparation process for the control experiments of SiO$^+$ is also described. We characterize the photoionization spectrum of neutral SiO for the purpose of loading an ion trap, we measure the SiO$^+$ optical branching ratios and lifetimes of states relevant to laser control, and we characterize the dissociating $X^2\Sigma^+\rightarrow C^2\Pi$ transition for state readout. Finally, we characterize the reaction rate of trapped SiO$^+$ with the background UHV environment. These steps described for SiO$^+$ are crucial for demonstrating control, and such a process could be generalized to other molecules of interest. In the remaining portions of the thesis I detail a proposal for optically pumping another molecule with diagonal FCFs, TeH$^+$, for the purpose of detecting a variation in the proton-to-electron mass ratio.

Creator

• Stollenwerk, Patrick R

DOI

• https://doi.org/10.21985/n2-n4ag-c149

Subject

• Molecular physics
• Quantum physics
• Atomic physics

Language

• en

Alternate Identifier

• etdadmin_upload_718268
• http://dissertations.umi.com/northwestern:14994

Keyword

• laser cooling
• quantum state control
• Ion traps
• SiO+

Date created

• 2020-01-01

Resource type

• Dissertation

Rights statement

• In Copyright