| 摘要 |
<p>A hyperpolarised material contains first and second hyperpolarisable nuclear species and a nuclear spin polarising agent. The first species may be 1H, has a higher magnetic moment (g), and is more abundant than the second species, which may be 13C or 15N. Microwave energy excites electron spin transitions in the polarising agent in a magnetic field (Bo). The first species thereby interacts with the electron spins in the polarising agent to generate hyperpolarisation. The material is then subjected to a lower magnetic field to transfer polarisation by nuclear thermal mixing, and thereby hyperpolarise the second species. The apparatus includes a cryostat (1), a material holder (4), a magnet (2) producing magnetic field (Bo), and a microwave source. A second magnet (6), with an opposed magnetic field, produces a "mixing field", low enough that the Zeeman energy of the two species is comparable to their dipolar interaction energy, and a device moves the material through the mixing field, to transfer nuclear polarisation between the species.</p> |
