Sören Lehmkuhl received his PhD in chemistry from the RWTH Aachen University on the subject of hyperpolarization with parahydrogen in NMR (nuclear magnetic resonance). In the working group of Prof. Dr. Bernhard Blümich, he worked on a modular immobilization system for hyperpolarization catalysts, a membrane reactor for continuous flow hyperpolarization, the first water hyperpolarization with parahydrogen. Moreover, in cooperation with the group of Prof. Dr. Stephan Appelt, he was part of the team that discovered the parahydrogen fueled NMR RASER (radio wave amplification by stimulated emission of radiation). For these efforts, he was awarded with the Borcher’s Badge for an excellent PhD thesis (summa cum laude).

From March 2019 until September 2021, he helped build up the hyperpolarization laboratory of Prof. Dr. Thomas Theis at the North Carolina State University of Raleigh. During that time he developed parahydrogen based technologies for applications, ranging from miniaturized NMR to in vivo hyperpolarized MRI (Magnetic Resonance Imaging). During the time, he also kept developing the RASER concept.

In June 2021, he was awarded a YIG Prep Pro Fellowship at KIT (Young investigator group preparation program). Over the two year course of this program, he aims to start his own junior research group combining the power of the NMR RASER with micro technologies. To realize this vision, he joined the Institute of Microstructure Technology (IMT) in October 2021.

Previous research

Hyperpolarized NMR and MRI using parahydrogen:

NMR and MRI are analytical tools routinely used in many fields of science and technology today. Applications range from structure or material characterization in chemistry and material science to clinical diagnosis.

To shorten measurement times and increase resolution, NMR and MRI crave for higher sensitivity. The desired high levels of polarization can be accessed by hyperpolarization methods such as parahydrogen based hyperpolarization. In this way, NMR signals many orders of magnitude higher than standard NMR can be generated within seconds. NMR spectra can be recorded during continuous flow conditions, while new parahydrogen is introduced outside of the magnet (e.g. by a membrane reactor).

First setup for continuous flow hyperpolarization with parahydrogen

Images from https://doi.org/10.1016/j.jmr.2018.03.012

The RASER concept:

The RASER is analogous in many ways to its well-known “brother” the Laser, but based on radio waves instead of light. In 2017, such coherent spontaneous emission in an NMR experiment pumped by parahydrogen hyperpolarization was achieved for the first time. This emission can be acquired over long periods of time (in theory indefinitely) as it does not decay in contrast to standard NMR. In this way, unprecedented precision in NMR could be obtained with resolution below the mHz regime. Alternatively, when choosing the right experimental conditions, nonlinear effects can be studied. They range from phenomena such as line collapse, frequency combs, period doubling and ultimately chaos.

Exploring chaos with a RASER

Image from https://doi.org/10.1016/j.jmr.2020.106815