气相凝聚的类富勒烯碳纳米颗粒的远紫外-红外光谱特性
Spectral properties of gas-phase condensed fullerene-like carbon nanoparticles from far-ultraviolet to infrared wavelengths
摘要：
碳固体是星际空间中普遍存在的物质。然而，碳质物质在天体物理环境中以及在陆地气相凝聚反应中的形成途径还不清楚。在不同的淬火气体气氛中，如纯He，He/H $_2$，和He/H $_2$ O在不同的压力下的石墨的激光烧蚀用于合成非常小的，富勒烯样碳纳米颗粒。颗粒的特征在于非常小的直径在1和4 nm之间，并且具有扰乱的洋葱状结构。从冷凝区提取的烟灰颗粒显然代表颗粒冷凝的非常早期的阶段。从远紫外（FUV）（$λ$ =120 nm）到中红外（MIR）（$λ$ =15 ~ $μ$ m）测量了光谱性质。在3.4 ~ $μ$ m范围内，种子状碳烟粒子具有较强的吸收带。用凝聚态粒子的3.4 ~ $μ$ m谱线可以很好地再现星际介质中3.4 ~ $μ$ m谱线的分布和强度，但要拟合星际谱线的强度，还需要保留全部的碳原子。与洋葱状烟灰颗粒可能是星际紫外线（UV）碰撞的载体的假设相反，我们的非常小的洋葱状碳纳米颗粒由于（$π-π$ *）跃迁而没有显示出明显的UV带。
英文摘要：
Carbon solids are ubiquitous material in the interstellar space. However, the formation pathway of carbonaceous matter in astrophysical environments as well as in terrestrial gas-phase condensation reactions is not yet understood. Laser ablation of graphite in different quenching gas atmospheres such as pure He, He/H$_2$, and He/H$_2$O at varying pressures is used to synthesize very small, fullerene-like carbon nanoparticles. The particles are characterized by very small diameters between 1 and 4 nm and a disturbed onion-like structure. The soot particles extracted from the condensation zone obviously represent a very early stage of particle condensation. The spectral properties have been measured from the far-ultraviolet (FUV) ($λ$=120 nm) to the mid-infrared (MIR) ($λ$=15 ~$μ$m). The seed-like soot particles show strong absorption bands in the 3.4 ~$μ$m range. The profile and the intensity pattern of the 3.4 ~$μ$m band of the diffuse interstellar medium can be well reproduced by the measured 3.4 ~$μ$m profile of the condensed particles, however, all the carbon which is left to form solids is needed to fit the intensity of the interstellar bands. In contrast to the assumption that onion-like soot particles could be the carrier of the interstellar ultraviolet (UV) bump, our very small onion-like carbon nanoparticles do not show distinct UV bands due to ($π-π$*) transitions.
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