Kouskov V, Sloop D J, Liu S B, Lin T S
Department of Chemistry, Washington University, St. Louis, Missouri, 63130, USA.
J Magn Reson. 1999 Mar;137(1):25-8. doi: 10.1006/jmre.1998.1660.
Properly prepared pulse sequences of microwave and radio frequency have been employed to investigate the effect of polarization transfer from the polarized photo excited triplet state of pentacene in p-terphenyl crystals to the surrounding protons in pulsed ENDOR experiments. The ENDOR signal, measured as the change of electron spin echo (ESE) amplitude, is affected by the mode of RF pulses. When B0 parallelx (the long molecular axis), the ESE amplitude of the high-field transition of the triplet state changes from the maximum positive to zero with a pi RF pulse, and to the maximum negative with a 2pi pulse, while that of the low-field transition changes from nearly zero to the maximum negative as the RF pulse width increases. The effect is attributed to the strong electron spin polarization produced in the creation of the photoexcited triplet state and the subsequent efficient electron- nuclear polarization transfer process.
在脉冲电子核双共振（ENDOR）实验中，已采用适当制备的微波和射频脉冲序列来研究并五苯在对三联苯晶体中的光激发三重态的极化转移对周围质子的影响。作为电子自旋回波（ESE）幅度变化测量的ENDOR信号受射频脉冲模式的影响。当B0平行于x（分子长轴）时，三重态高场跃迁的ESE幅度在施加π射频脉冲时从最大正值变为零，在施加2π脉冲时变为最大负值，而低场跃迁的ESE幅度则随着射频脉冲宽度增加从几乎为零变为最大负值。这种效应归因于光激发三重态产生时产生的强电子自旋极化以及随后有效的电子 - 核极化转移过程。
