Zhou Shushan, Wang Hao, Yu Dongming, Xu Nan, Hu Muhong
School of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029, China.
Molecules. 2025 May 12;30(10):2133. doi: 10.3390/molecules30102133.
High-order harmonic generation provides a powerful tool for probing ultrafast chemical dynamics, such as electron transfer, bond breaking, and molecular structural changes, with attosecond temporal resolution. The strong laser fields used in HHG can also directly influence chemical reaction pathways and rates, enabling coherent control of reaction selectivity. However, enhancing the efficiency of harmonic emission remains a critical challenge in ultrafast science. In this study, we investigate the effects of molecular size and orientation on HHG efficiency using time-dependent density functional theory simulations. By analyzing the linear molecules C18H2, C2H2, and CH under linearly polarized laser fields, we demonstrate that larger molecular sizes significantly enhance harmonic emission intensity. Our results reveal that C18H2, with its larger spatial dimensions, exhibits substantially higher harmonic intensity compared to smaller molecules like C2H2. This enhancement is further supported by examining charge redistribution and bond length changes during the HHG process. Additionally, we validate our findings with CH, a molecule of intermediate size, confirming the correlation between molecular size and harmonic efficiency.
高次谐波产生为探测超快化学动力学提供了一个强大的工具，例如电子转移、键断裂和分子结构变化，具有阿秒级的时间分辨率。高次谐波产生中使用的强激光场也可以直接影响化学反应路径和速率，从而实现对反应选择性的相干控制。然而，提高谐波发射效率仍然是超快科学中的一个关键挑战。在本研究中，我们使用含时密度泛函理论模拟来研究分子大小和取向对高次谐波产生效率的影响。通过分析线性分子C18H2、C2H2和CH在线偏振激光场下的情况，我们证明更大的分子尺寸会显著增强谐波发射强度。我们的结果表明，与C2H2等较小的分子相比，具有更大空间尺寸的C18H2表现出更高的谐波强度。在高次谐波产生过程中通过检查电荷重新分布和键长变化进一步支持了这种增强。此外，我们用中等大小的分子CH验证了我们的发现，证实了分子大小与谐波效率之间的相关性。
