Echo phenomena is a cornerstone in coherent spectroscopy. Echos – often referred to as time-reversal elements - are key ingredients in advanced NMR, EPR, IR, microwave, and laser spectroscopies. In a study, published in Science Advances, iNANO researchers have, for the first time, demonstrated that it is possible to invert effective electron-nuclear spin hyperfine interactions in pulsed DNP and thereby form so-called DNP echos.

The researchers used advanced spin engineering to generate pulse sequences that inverts the sign of the effective hyperfine coupling interaction. The pulse sequences were implemented on a newly built pulsed DNP/EPR spectrometer using fast arbitrary waveform generators on microwave and radio-frequency channels. This enabled experimental observation of the DNP echo phenomena for a sample containing trityl radicals. Echoes formed at the nuclear spin channel (NMR) and electron spin channel (EPR) are illustrated in the figure above.

The realization of DNP echos phenomena may form a breakthrough in the development of pulsed DNP experiments boosting the sensitivity of NMR by orders of magnitude. One could envisage high-sensitivity detection of nuclear spin coupling networks surrounding electron spins. Such experiments could be of great interest for quantum sensing applications.

Study type:
Nanotechnology, Experimental physics

External funding:
This project has received funding from the Novo Nordisk Foundation (NERD grant NNF 22OC0076002), the Swiss National Science Foundation (Postodc Mobility grant 206623), and Aarhus University Research Foundation (AUFF-E-2021-9-22)

Conflicts of interest:
The authors declare no competing financial interest.

Link to the scientific article:
https://www.science.org/doi/10.1126/sciadv.adr2420

Nino Wili, Anders Bodholt Nielsen, José Carvalho, Niels Chr. Nielsen

Contact information:
Dr. Nino Wili
Quad Systems Ltd
Dietlikon, Switzerland
Email: science@nwili.ch

Prof. Niels Chr. Nielsen
iNANO and Department of Chemistry
Aarhus University
Email: ncn@chem.au.dk