In this award funded by the Experimental Physical Chemistry Program, Professor Romalis of Princeton University will develop a new detection method for nuclear magnetic resonance (NMR) spectroscopy. NMR is a versatile technique used in clinical medicine, medical research, basic biology, chemistry, and many other fields. It is widely used for studying proteins and other biologically-important molecules, and for non-invasive Magnetic Resonance Imaging (MRI) for medical diagnostics. The vast majority of these applications rely on inductive detection of long-range dipolar magnetic fields created by spin-polarized liquids and solids, the technique prevalent since the inception of NMR. In this project, Professor Romalis will develop a new method for NMR detection using optical rotation of a laser beam passing through the sample. This new method of nuclear spin optical rotation (NSOR) opens a number of new possibilities for NMR spectroscopy and imaging.
Professor Romalis and his students will develop a measurement apparatus that allows detection of NSOR signals in a standard 5-mm NMR probe using an optical cavity to increase the signal-to-noise by a factor of 2000. Four directions for initial exploration of the optical detection method are envisioned:
First, measurements on common fluids will allow basic understanding of the range of NSOR signals and comparison with previous theoretical calculations of this effect. Second, measurements on molecules with strong isolated absorption peaks in the visible spectrum would allow studies of hyperfine interactions near optical centers. Third, measurements on compounds with heavy elements would identify particularly strong NSOR signals that could be used as markers for direct optical imaging of NMR. Fourth, measurements on molecules with several groups of non-equivalent nuclei will explore the specificity of the NSOR signals and their relationship to chemical shifts.
The technical designs will be shared with the community and efforts will be made to commercialize the technology. The project will provide cross-disciplinary training opportunities for students and postdoctoral researchers.
Nuclear magnetic resonance is used in many scientific and medical applications, such as magnetic resonance imaging (MRI). It is usually detected by measuring a voltage induces in a coil of wire. In this project we explored a different method for detecting nuclear magnetic resonance signals by shinning light through the sample. We measure the properties of the light after it passes through the sample and interacts with magnetic nuclei. This method of signal detection provides new information about the chemical evironment and can be used to distinguish different substances. To investigate this phenomenon we constructed a system with mirrors that allows light to pass many times through a sample in order to increase the signal. We then flowed difference chemicals in the system and measured their optical signals. We have shown, for the first time, that optical signals depend on the chemical structure and thus provide different information from that of a signal in a wire coil. We then investigated a more ambitious approach where an optical fiber is used to hold the sample and send light through it. It will allow measurements on a much smaller sample volume. We have obtained preliminary results that showed that this approach is feasible. The majority of this work was conducted by a graduate student. The student has defended his disseratation and received a PhD in Chemistry based on this work. The results have also been published in a scientific article.
