Venâncio Tiago, Engelsberg Mario, Azeredo Rodrigo B V, Colnago Luiz A
Universidade de São Paulo, Instituto de Química de São Carlos, Avenida Trabalhador São-Carlense 400, São Carlos, SP 13560-590, Brazil.
J Magn Reson. 2006 Jul;181(1):29-34. doi: 10.1016/j.jmr.2006.03.011. Epub 2006 Apr 17.
Continuous wave free precession (CWFP) nuclear magnetic resonance is capable of yielding quantitative and easily obtainable information concerning the kinetics of processes that change the relaxation rates of the nuclear spins through the action of some external agent. In the present application, heat flow from a natural rubber sample to a liquid nitrogen thermal bath caused a large temperature gradient leading to a non-equilibrium temperature distribution. The ensuing local changes in the relaxation rates could be monitored by the decay of the CWFP signals and, from the decays, it was possible to ascertain the prevalence of a diffusive process and to obtain an average value for the thermal diffusivity.
连续波自由进动（CWFP）核磁共振能够提供有关动力学过程的定量且易于获取的信息，这些过程通过某些外部因素的作用改变核自旋的弛豫速率。在本应用中，从天然橡胶样品到液氮热浴的热流导致了较大的温度梯度，从而产生了非平衡温度分布。随后弛豫速率的局部变化可以通过CWFP信号的衰减来监测，并且从这些衰减中，可以确定扩散过程的普遍性并获得热扩散率的平均值。
