The confinement energy of electrons in an aromatic molecule was studied by indirect and direct methods, namely, temperature-dependent photoluminescence (TDPL) spectroscopy and scanning tunneling microscopy (STM). We observed a decrease in the tetraphenylporphyrin (H₂TPP) PL intensity with increasing temperature. The increase in temperature provides kinetic energy for the electrons to overcome the confinement energy barrier, making recombination via nonradiative pathways more favorable. The results of fitting the integrated TDPL intensity with a modified Arrhenius equation suggest two confinement energy values. We propose that these energy values are related to the size of the delocalized electron cloud along the plane and thickness of the H₂TPP ring. These values quantitatively express an abstract form of the size of the aromatic ring system. These results are in good agreement with the topography images of single H₂TPP molecules and monolayer H₂TPP obtained by a direct probing method using STM. These results are also supported by the porphyrin ring orientation relative to the excited crystal face during the TDPL measurements.

中文翻译：

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通过依赖温度的光致发光光谱进行量子限制探测，揭示卟啉分子的实际大小

通过间接和直接方法，即温度依赖性光致发光（TDPL）光谱和扫描隧道显微镜（STM），研究了芳香族分子中电子的束缚能。我们观察到四苯基卟啉（H ₂ TPP）PL强度随温度升高而降低。温度的升高为电子提供了克服限制能垒的动能，从而使通过非辐射途径的复合更为有利。用修正的Arrhenius方程拟合TDPL积分强度的结果表明了两个约束能量值。我们建议这些能量值与沿着该平面的H _2的厚度和离域电子云的大小有关TPP环。这些值定量表示芳族环系统的大小的抽象形式。这些结果与通过使用STM的直接探测方法获得的单个H ₂ TPP分子和单层H ₂ TPP的形貌图像非常吻合。在TDPL测量中，卟啉环相对于受激晶面的取向也支持了这些结果。