Coherent excitation of a molecular ensemble coupled to a common radiation mode can lead to the collective emission of radiation known as superradiance. This collective emission only occurs if there is an entanglement between the molecules in their ground and excited state and can therefore serve as a macroscopic measure of coherence in the ensemble. Reported here are wave packet propagations for various pyrazine models of increasing complexity and molecular ensembles thereof. We show that ensemble coherence upon photoexcitation can prevail up to relatively long time scales, although the effect can diminish quickly with increasing ensemble size. Coherence can also build up over time and even reemerge after the molecules have passed through a conical intersection. The effect of the pump-pulse characteristics on the collective response of the molecular ensemble is also studied. A broad-band pulse imprints a large amount of initial coherence to the system, as compared to a longer pulse with a smaller spread in the frequency domain. However, the differential effects arising from a different pulse duration and coherent bandwidth become less prominent if the emission of light from the ensemble takes place after a non-adiabatic decay process.

中文翻译：

---

腔中有机分子的多光子激发-超辐射作为相干性的量度

与共同辐射模式耦合的分子集合体的相干激发会导致被称为超辐射的辐射的集体发射。仅当分子在其基态和受激态之间存在纠缠时才发生这种集体发射，因此可以用作整体中相干性的宏观度量。这里报道的是各种吡嗪模型的波包传播，这些吡嗪模型的复杂性及其分子集合不断增加。我们表明，在光激发下，整体相干可以在相对较长的时间尺度上占主导地位，尽管随着整体尺寸的增加，其影响会迅速减小。相干性还可以随着时间的流逝而建立，甚至在分子通过圆锥形相交点后重新出现。还研究了泵浦脉冲特性对分子整体响应的影响。与更长的脉冲相比，宽带脉冲在系统上具有大量的初始相干性，而在频域中扩展性较小。但是，如果在非绝热衰减过程之后发生合奏发出的光，则由不同的脉冲持续时间和相干带宽引起的微分效应变得不太明显。