Dynamic nuclear polarisation via the integrated solid effect II: experiments on naphthalene-h8 doped with pentacene-d14
Dynamic nuclear polarisation via the integrated solid effect II: experiments on naphthalene-h8 doped with pentacene-d14
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DOI：
10.1080/00268976.2013.863405
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发表时间：
2014-01-01
影响因子：
1.7
通讯作者：
Wenckebach, W. Th
中科院分区：
文献类型：
--
作者：
Eichhorn, T. R.;van den Brandt, B.;Wenckebach, W. Th
在动态核极化（DNP）中，也称为超极化，向含有核自旋的样品中加入少量未成对电子自旋，并且这些未成对电子自旋的极化通过微波场转移到核自旋上。传统的DNP通过冷却到低温并施加强磁场使稳定的顺磁中心的电子自旋极化。然后使用弱连续波微波场来诱导极化转移。利用在光激发过程中强烈取向的短寿命光激发三重态，可以避免使用复杂的低温设备和强磁体。然而，需要更快的电子自旋极化转移，并且使用诸如通过电子自旋锁定的核取向（NOVEL）和集成固体效应（ISE）等脉冲DNP方法。为了描述在NOVEL和ISE中强微波场下的极化转移，常用的微扰方法不再适用。在之前的论文中，我们提出了一种计算ISE中极化转移的理论方法。在本文中，该理论应用于掺杂并五苯 - d(14)产生光激发三重态的萘 - h(8)体系，并与实验结果进行了比较。
In dynamic nuclear polarisation (DNP), also called hyperpolarisation, a small amount of unpaired electron spins is added to the sample containing the nuclear spins, and the polarisation of these unpaired electron spins is transferred to the nuclear spins by means of a microwave field. Traditional DNP polarises the electron spin of stable paramagnetic centres by cooling down to low temperature and applying a strong magnetic field. Then weak continuous wave microwave fields are used to induce the polarisation transfer. Complicated cryogenic equipment and strong magnets can be avoided using short-lived photo-excited triplet states that are strongly aligned in the optical excitation process. However, a much faster transfer of the electron spin polarisation is needed and pulsed DNP methods like nuclear orientation via electron spin locking (NOVEL) and the integrated solid effect (ISE) are used.To describe the polarisation transfer with the strong microwave fields in NOVEL and ISE, the usual perturbation methods cannot be used anymore. In the previous paper, we presented a theoretical approach to calculate the polarisation transfer in ISE. In the present paper, the theory is applied to the system naphthalene-h(8) doped with pentacene-d(14) yielding the photo-excited triplet states and compared with experimental results.