The Dynamic Nuclear Polarization (DNP) means we has a pumping source to change the population of nuclear spin, then create a polarization. in contrast, Static Nuclear Polarization (SNP) means thermal equilibrium of nuclear state population.
the introduction of the paper gives 7 applications on polarized nuclear spin.i only list some below:
- the angular distribution on radiations can serve as a test on the theory of nuclear interaction
- Polarized target can be used in scatter experiment
- obtain detail information on static and dynamic interaction between nuclear spin and its environment.
- increase the sensitivity of NMR
this paper focus on a general system and represents them by graphs ( called chart in the paper ). the graphs are based on electron spin ½ and nuclear spin also ½.
on section II, it give out the Spin Hamiltonian and use it for the discussion on the population distribution. by that, the author used the rate equations to related the population in each state. Then, he defined the Enhancement of polarization, which is the ratio between the population with saturating radiation to the thermal thermal distribution.
on section III, it mention about the first 2 successful dynamic nuclear polarization experiments around 1953-4. one group polarized the 6Li nucleus in metallic lithium. the other group polarized the 1H in solid DPPH.
The paper gives conditions for DNP, which is coupling between nuclear spin and an unpaired electron spin. the paramagnetic environment can be archived by
- the conduction electron in metals or metal ammonia solution
- the donor or acceptor electrons in semi-conductor
- paramagnetic ions in diamagnetic solid
- paramagnetic ions in solution
- free radical
- color centers
the detection of DNP can be via:
- shift of EPR frequency
- the β asymmetry or γ anisotropy from an oriented radioisotope