Magnetic Resonance
Magnetic Resonance
Magnetic Resonance
Preprints
https://doi.org/10.5194/mr-2020-36
https://doi.org/10.5194/mr-2020-36

  15 Dec 2020

15 Dec 2020

Review status: this preprint is currently under review for the journal MR.

Room temperature hyperpolarization of polycrystalline samples with optically polarized triplet electrons: Pentacene or Nitrogen-Vacancy center in diamond?

Koichiro Miyanishi1, Takuya F. Segawa2,3, Kazuyuki Takeda4, Izuru Ohki5, Shinobu Onoda6,7, Takeshi Ohshima6,7, Hiroshi Abe6,7, Hideaki Takashima8, Shigeki Takeuchi8, Alexander I. Shames9, Kohki Morita5, Yu Wang4, Frederick T.-K. So2,6, Daiki Terada2,6, Ryuji Igarashi6,7,10, Akinori Kagawa1,10,11, Masahiro Kitagawa1,11, Norikazu Mizuochi5, Masahiro Shirakawa2,6, and Makoto Negoro6,10,11 Koichiro Miyanishi et al.
  • 1Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
  • 2Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-Ku, Kyoto 615-8510, Japan
  • 3Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
  • 4Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
  • 5Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
  • 6Institute for Quantum Life Science, National Institutes for Quantum and Radiological Science and Technology, 4-9-1, Anagawa, Inage-Ku, Chiba 263-8555, Japan
  • 7Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
  • 8Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
  • 9Department of Physics, Ben-Gurion University of the Negev, 8410501 Beer-Sheva, Israel
  • 10JST, PRESTO, Kawaguchi, Japan
  • 11Quantum Information and Quantum Biology Center, Institute for Open and Transdisciplinary Research Initiatives, Osaka University, Japan

Abstract. We demonstrate room-temperature 13C hyperpolarization by dynamic nuclear polarization (DNP) using optically polarized triplet electron spins in two polycrystalline systems: pentacene-doped [carboxyl-13C] benzoic acid and microdiamonds containing NV- centers. For both samples, the integrated solid effect (ISE) is used to polarize the 13C spin system in magnetic fields of 350–400 mT. In the benzoic acid sample, the 13C spin polarization is enhanced up to 0.12 % through direct electron-to-13C polarization transfer without performing dynamic 1H polarization followed by 1H-13C cross polarization. In addition, ISE has been successfully applied for the first time to polarize naturally abundant 13C spins in a microdiamond sample to 0.01 %. To characterize the buildup of the 13C polarization, we discuss the efficiencies of direct polarization transfer between the electron and 13C spins as well as that of 13Cā€“13C spin diffusion, examining various parameters which are beneficial or detrimental for successful bulk dynamic 13C polarization.

Koichiro Miyanishi et al.

 
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Koichiro Miyanishi et al.

Koichiro Miyanishi et al.

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Short summary
13C spin hyperpolarization using laser irradiation at room temperature is shown in two different systems: 1. Pentacene doped in an organic crystal of benzoic acid and 2. Nitrogen-Vacancy (NV) color centers in microdiamonds. The 13C NMR signal was enhanced by a factor of > 3000 using pentacene and > 300 using NV centers as a polarization source. We analyze the pros and cons of these two systems and discuss their prospects for room-temperature enhancement of NMR signals.