论文标题
X射线自由电子激光器诱导的液体喷射爆炸和冲击波的分子模拟
Molecular Simulations of Liquid Jet Explosions and Shock Waves Induced by X-Ray Free-Electron Lasers
论文作者
论文摘要
X射线自由电子激光器（XFELS）产生具有高光彩和短脉冲持续时间的X射线脉冲。这些特性可以对生物分子纳米晶体进行结构研究，并允许将生物分子的动力学分解为飞秒时间尺度。液体喷气机被广泛用于将样品输送到Xfel束中。 X射线脉冲的影响会导致液体射流的蒸发和爆炸，而膨胀的气体会触发沿着喷气式飞机行驶的冲击波序列的形成，这可能会在探测之前会影响生物分子样品。在这里，我们使用分子动力学模拟来揭示X射线冲击后冲击波的结构动力学。对射流中的密度的分析显示，靠近爆炸中心的冲击波，以超音速速度沿着喷气机行驶，并呈指数衰减，衰减长度与射流直径成正比。在第一次冲击波后形成的尾随冲击波类似于实验中的冲击波列。尽管在模拟中使用了纯粹的经典模型，但所得的爆炸几何形状和冲击波动力学与实验发现非常相似，它们强调了原子细节对于对冲击波衰减进行建模的重要性。
X-ray free-electron lasers (XFELs) produce X-ray pulses with high brilliance and short pulse duration. These properties enable structural investigations of biomolecular nanocrystals, and they allow resolving the dynamics of biomolecules down to the femtosecond timescale. Liquid jets are widely used to deliver samples into the XFEL beam. The impact of the X-ray pulse leads to vaporization and explosion of the liquid jet, while the expanding gas triggers the formation of shock wave trains traveling along the jet, which may affect biomolecular samples before they have been probed. Here, we used molecular dynamics simulations to reveal the structural dynamics of shock waves after an X-ray impact. Analysis of the density in the jet revealed shock waves that form close to the explosion center, travel along the jet with supersonic velocities and decay exponentially with an attenuation length proportional to the jet diameter. A trailing shock wave formed after the first shock wave, similar to the shock wave trains in experiments. Although using purely classical models in the simulations, the resulting explosion geometry and shock wave dynamics closely resemble experimental findings, and they highlight the importance of atomistic details for modeling shock wave attenuation.
