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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >An electronic time scale in chemistry
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An electronic time scale in chemistry

机译：电子化学时标

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Ultrafast, subfemtosecond charge migration in small peptides is discussed on the basis of computational studies and compared with the selective bond dissociation after ionization as observed by Schlag and Weinkauf. The reported relaxation could be probed in real time if the removal of an electron could be achieved on the attosecond time scale. Then the mean field seen by an electron would be changing rapidly enough to initiate the migration. Tyrosine-terminated tetrapeptides have a particularly fast charge migration where in < 1 fs the charge arrives at the other end. A femtosecond pulse can be used to observe the somewhat slower relaxation induced by correlation between electrons of different spins. A slower relaxation also is indicated when removing a deeper-lying valence electron. When a chromophoric amino acid is at one end of the peptide, the charge can migrate all along the peptide backbone up to the N end, but site-selective ionization is probably easier to detect for tryptophan than for tyrosine.
机译：在计算研究的基础上，讨论了小肽中的超快速亚飞秒电荷迁移，并与电离后的选择性键解离（如Schlag和Weinkauf所观察到的）进行了比较。如果可以在十亿分之一秒的时间范围内实现电子的去除，则可以实时探测所报告的弛豫。然后，电子看到的平均场将迅速变化，足以引发迁移。酪氨酸末端的四肽具有特别快的电荷迁移，电荷在<1 fs内到达另一端。飞秒脉冲可用于观察由不同自旋的电子之间的相关性引起的稍慢的弛豫。当移出更深的价电子时，也显示出较慢的松弛。当发色氨基酸位于肽的一端时，电荷可沿肽主链全部迁移至N端，但是色氨酸的检测比酪氨酸的检测更容易进行。

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