We present a comparative investigation on static equilibrium and transient structural dynamics of nanocrystalline gold films on silicon nitride supports performed at various in situ temperatures and by ultrafast laser excitations in a four-dimensional ultrafast transmission electron microscope (4D-UTEM). The change of relative diffraction intensity and lattice spacing with rising temperatures was systematically measured for {220} Debye–Scherrer rings via the in situ heating technique, which leads to a precise determination of the actual Debye temperature and a finding of significant depression of lattice expansions in the films. The diffraction intensity/lattice spacing–temperature relationship calibrated by the static, thermally equilibrium observations was then employed for investigating ultrafast transient dynamics on the same specimen region. The electron–phonon coupling constant g was determined to be 7.2 × 10¹⁵ W/m³ K in combination with simple two-temperature model analysis. We found a marked variation of temperature rise maximum (at quasi-equilibrium states) in between the temporal evolutions of lattice spacing and diffraction intensity, a phenomenon which may only be explained by the effect of nonthermal equilibrium relaxation dynamics following femtosecond laser excitations. The method demonstrated here can thus be applied to quantitative evaluations of nonthermal equilibrium contributions during the electron–lattice thermalization.

中文翻译：

---

通过结合原位热加热和飞秒激光激发在4D透射电子显微镜中揭示纳米晶体膜中的电子-声子相互作用和晶格动力学

我们目前在各种原位温度下，通过在四维超快透射电子显微镜（4D-UTEM）中通过超快激光激发，对氮化硅载体上的纳米晶体金膜的静态平衡和瞬态结构动力学进行了比较研究。通过原位加热技术系统地测量了{220} Debye-Scherrer环的相对衍射强度和晶格间距随温度升高的变化，从而可以精确确定实际的德拜温度，并发现晶格膨胀的显着降低在电影中。然后通过静态，热平衡观测值校准的衍射强度/晶格间距与温度的关系，用于研究同一样本区域上的超快速瞬态动力学。克经测定为7.2×10 ¹⁵ W /米³ K的与简单的两温度模型分析组合。我们发现在晶格间距和衍射强度的时间演化之间最大的温升最大值（在准平衡态）有明显的变化，这种现象只能由飞秒激光激发后的非热平衡弛豫动力学的影响来解释。因此，这里展示的方法可以用于电子-晶格热化过程中非热平衡贡献的定量评估。