On Graphene in the Interstellar Medium
On Graphene in the Interstellar Medium
复制标题
论星际介质中的石墨烯
DOI：
10.3847/1538-4357/aa93d5
复制
发表时间：
2017-11-20
影响因子：
4.9
通讯作者：
Zhang, Ke
中科院分区：
文献类型：
--
作者：
Chen, X. H.;Li, Aigen;Zhang, Ke
C-24是一种平面石墨烯，最近由Garcia-Hernandez等人报道存在于几个行星星云中，这一可能的探测激发了我们探索星际介质(ISM)中是否存在石墨烯以及存在多少石墨烯，以及它如何通过紫外线(UV)消光和红外(IR)发射揭示其存在。原则上，星际石墨烯可能来自ISM中丰富的多环芳烃(PAH)分子的光化学处理，因为它们的氢原子完全消失，和/或来自被认为是ISM中主要尘埃物种的石墨，通过颗粒-颗粒碰撞破碎引起的碎裂。量子化学计算和实验室实验都表明，石墨烯中激子主导的电子跃迁在2755埃附近产生了一个强吸收带。我们计算了石墨烯的紫外吸收，并给星际石墨烯丰度设定了类似于5ppm的C/H(即类似于星际总C的1.9%)的上限。我们还模拟了石墨烯C-24在星际辐射场的单星光光子激发下的随机加热，并计算了它的红外发射光谱。我们还推导出石墨烯在ISM中的丰度为
The possible detection of C-24, a planar graphene that was recently reported to be in several planetary nebulae by Garcia-Hernandez et al., inspires us to explore whether and how much graphene could exist in the interstellar medium (ISM) and how it would reveal its presence through its ultraviolet (UV) extinction and infrared (IR) emission. In principle, interstellar graphene could arise from the photochemical processing of polycyclic aromatic hydrocarbon (PAH) molecules, which are abundant in the ISM, due to the complete loss of their hydrogen atoms, and/or from graphite, which is thought to be a major dust species in the ISM, via fragmentation caused by grain-grain collisional shattering. Both quantum-chemical computations and laboratory experiments have shown that the exciton-dominated electronic transitions in graphene cause a strong absorption band near 2755 angstrom. We calculate the UV absorption of graphene and place an upper limit of similar to 5 ppm of C/H (i.e., similar to 1.9% of the total interstellar C) on the interstellar graphene abundance. We also model the stochastic heating of graphene C-24 in the ISM, excited by single starlight photons of the interstellar radiation field and calculate its IR emission spectra. We also derive the abundance of graphene in the ISM to be