We present time-resolved ultraviolet-pump x-ray probe Auger spectra of 2-thiouracil. An ultraviolet induced shift towards higher kinetic energies is observed in the sulfur 2p Auger decay. The difference Auger spectra of pumped and unpumped molecules exhibit ultrafast dynamics in the shift amplitude, in which three phases can be recognized. In the first 100fs, a shift towards higher kinetic energies is observed, followed by a 400fs shift back to lower kinetic energies and a 1ps shift again to higher kinetic energies. We use a simple Coulomb-model, aided by quantum chemical calculations of potential energy states, to deduce a C–S bond expansion within the first 100fs. The bond elongation triggers internal conversion from the photoexcited S₂ to the S₁ state. Based on timescales, the subsequent dynamics can be interpreted in terms of S₁ nuclear relaxation and S₁-triplet internal conversion.

我们提出了时间分辨的2-硫尿嘧啶的紫外线泵浦x射线探针俄歇光谱。在硫2p俄歇衰变中观察到紫外线引起的向更高动能的转变。泵浦和未泵浦分子的俄歇谱差在位移幅度方面表现出超快的动力学特性，其中可以识别出三个相位。在最初的100fs中，观察到向较高动能的转变，然后是400fs移回较低的动能，而1ps再次移至较高的动能。我们使用简单的库仑模型，借助势能态的量子化学计算，推导出前100fs内的CS键扩展。键的延伸触发了从光激发的S ₂到S _1的内部转化状态。基于时间尺度，随后的动力学可以根据S ₁核弛豫和S _1-三胞胎内部转化来解释。