 | Dynamic Nuclear Polarization Induced by Laser and Microwave
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| | Kazuyuki Takeda1), Kiyonori Takegoshi2) and Takehiko Terao1)2) |
| 1) JST-CREST
2) Department of Chemistry, Graduate School of Science, Kyoto University |
| | We are investigating a possibility of improving the NMR sensitivity using photo-excited electron spins. For this purpose, we are making fundamental studies on a dynamic nuclear polarization (DNP) technique by cross polarization with electron spins in the photo-excited triplet state on the basis of the Shmidt’s work [1]. The proton polarization obtained in a single crystal of either undeuterated or deuterated naphthalene doped with pentacene is essentially the same with the electron polarization of about 63%, indicating that the theoretically maximum polarization has been attained in the present experiment for the first time. The buildup time in deuterated naphthalene (357 s) is much shorter than in normal naphthalene (7890 s). We also succeeded in the DNP experiments in powder samples by limiting the field sweep range to the sharp peak width [2]. Even in the 60 mg powder sample of 99.2% deuterated naphthalene, a spectrum of the residual protons could be observed with high sensitivity in a single scan in the field of 0.3 T. Furthermore, we have created polarization at a low field and observed the spectrum at a high field using a sample shuttle system to improve the resolution. These results may be useful for improving the NMR sensitivity in chemically and biologically interesting systems and initializing the NMR quantum computer. |
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