碱金属纳米颗粒的温度依赖性光电离阈值揭示热膨胀和熔化转变
Temperature-dependent photoionization thresholds of alkali-metal nanoparticles reveal thermal expansion and the melting transition
AI总结：
通过高精度测量揭示碱金属纳米颗粒温度依赖性光电离阈值，发现其工作函数随温度变化并揭示熔化转变。
摘要：
对纯钠和钾纳米颗粒的光电离进行高精度测量，使能够准确确定其工作函数随温度变化的函数关系。除了解析并量化温度升高时工作函数的初始逐渐下降，这与热膨胀有关外，实验还发现工作函数随后经历幅度和斜率的显著下降，这标志着纳米颗粒熔化的开始。这表明，通过高分辨率的光电离阈值测量可以检测到结构相变。直径为7-9纳米的纳米颗粒的熔点比本体值降低了近100 K。这种抑制与Gibbs-Thomson方程的预测一致，该方程描述了有限尺寸相变。
英文摘要：
A precision measurement of the photoionization of pure sodium and potassium nanoparticles isolated in a beam enabled an accurate determination of their work functions as a function of temperature. In addition to resolving and quantifying the initial gradual decrease of the work function with temperature, which is associated with thermal expansion, the experiment revealed that the work function then undergoes a distinct drop both in magnitude and in slope that signifies the onset of nanoparticle melting. This establishes that a structural phase transition can be detected via a high-resolution measurement of the photoemission threshold. The melting temperature of nanoparticles with diameters of 7-9 nm is reduced by nearly 100 K relative to the bulk value. This suppression aligns with predictions from the Gibbs-Thomson equation which describes finite-size phase transitions.
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