Nuclear spin-induced optical rotation in low magnetic field

Abstract

Nuclear spin-induced optical rotation (NSOR) is a method that utilizes a polarized laser light that interacts with the electrons under the influence of nuclear magnetic moments of a molecule. The interaction yields a slight rotation in the polarization of the light beam that is proportional to the distance propagated in the sample medium, the spin polarization of the sample and the NSOR constant of the molecule. This yields information about the hyperfine structure of the molecules. The rotation can be detected by utilizing a set of optics and detectors that capture the x- and y- components of polarization of the laser after the propagation through the sample. The magnitude of the rotation is small, and therefore tricky to capture with samples of lower concentrations, without enhancing the polarization of the molecules under study. The polarization can be enhanced with several hyperpolarization methods. The hyperpolarization technique of choice for the work done for this thesis is SABRE hyperpolarization method that utilizes a transition-metal complex with para-hydrogen to transfer the polarization to the target molecule. This is possible due to the J- coupling network between the target molecule, the transition-metal complex and parahydrogen.

The experimental set-up requires a variety of components which are described in the thesis. One of the main considerations for the set-up are a set of optics for guiding a propagating beam of polarized laser light as well as for the analysis of the rotation induced during the propagation. To observe the rotation, the sample is placed in a set of magnetic fields generated by electromagnets. In addition to the magnetic fields for the measuring of the signal, a polarizing field for the sample must be present. To conduct continuous measurements, a set-up that polarizes the sample and transfers it to the measurement cell is used. The experimental set-up as well as the utilization of it is described in this thesis.

The focus of the work done in this thesis was to experiment with NSOR measurements with an existing instrument and optimize the setup. The other significant consideration was to utilize the SABRE hyperpolarization technique for a variety of samples to determine the suitability of the molecules for NSOR experiments