Spin-lattice relaxation of spin-½ nuclei in solids containing diluted paramagnetic impurity centers. II. Dynamic polarization of nuclear spin system by thermal mixing and solid-state effect

✍ Scribed by E.C. Reynhardt

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 237 KB
• Volume: 19A
• Category: Article
• ISSN: 1546-6086
• DOI: 10.1002/cmr.a.10078

✦ Synopsis

Abstract

Dynamic nuclear polarization of nuclear spins via the solid‐state and thermal mixing effects is discussed. Continuous‐wave S‐ and X‐band microwave radiation have been employed to measure ^13^C signal enhancements and polarization times for ^13^C nuclei in a natural type Ib diamond as a function of magnetic field. It was found that thermal mixing plays an important role in the ^13^C signal enhancement because the central electron spin resonance (ESR) line width H~L~ ≃ H~0~γ~C~/γ~e~, resulting in flip‐flip and flip‐flop forbidden transitions taking place simultaneously. On the other hand, the ^13^C spin‐lattice relaxation rate is determined to a large extent by the solid‐state effect (forbidden transitions). ^13^C polarization rates have also been measured for a suite of natural diamonds. It is shown that the polarization rate is proportional to the paramagnetic impurity concentration, in agreement with the theory. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson 19A: 36–43, 2003.