Chung Simon, Vonk Vedran, Pennicard David, Graafsma Heinz, Stierle Andreas
Centre for X-ray and Nano Science CXNS, Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany.
Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany.
Struct Dyn. 2024 Jul 3;11(4):044301. doi: 10.1063/5.0189052. eCollection 2024 Jul.
Pulsed laser heating of an ensemble of Pd nanoparticles, supported by a MgO substrate, is studied by x-ray diffraction. By time-resolved Bragg peak shift measurements due to thermal lattice expansion, the transient temperature of the Pd nanoparticles is determined, which quickly rises by at least 100 K upon laser excitation and then decays within 90 ns. The diffraction experiments were carried out using a Cu x-ray tube, giving continuous radiation, and the hybrid pixel detector Timepix3 operating with single photon counting in a time-of-arrival mode. This type of detection scheme does not require time-consuming scanning of the pump-probe delay. The experimental time resolution is estimated at 15 ± 5 ns, which is very close to the detector's limit and matches with the 7 ns laser pulse duration. Compared to bulk metal single crystals, it is discussed that the maximum temperature reached by the Pd nanoparticles is higher and their cooling rate is lower. These effects are explained by the oxide support having a lower heat conductivity.
通过X射线衍射研究了由MgO衬底支撑的Pd纳米颗粒集合体的脉冲激光加热。通过热晶格膨胀引起的时间分辨布拉格峰位移测量，确定了Pd纳米颗粒的瞬态温度，在激光激发时该温度迅速升高至少100 K，然后在90 ns内衰减。衍射实验使用产生连续辐射的Cu X射线管以及在到达时间模式下以单光子计数运行的混合像素探测器Timepix3进行。这种检测方案不需要对泵浦-探测延迟进行耗时的扫描。实验时间分辨率估计为15±5 ns，非常接近探测器的极限，并且与7 ns的激光脉冲持续时间相匹配。与块状金属单晶相比，讨论了Pd纳米颗粒达到的最高温度更高且其冷却速率更低。这些效应由具有较低热导率的氧化物载体来解释。
