In an experiment, cyclo[18]carbon (C₁₈), prepared with low-temperature STM-AFM (scanning tunneling microscopy-atomic force microscopy) from C₂₄O₆, C₂₂O₄, and C₂₀O₂ molecules, have been confirmed being alternating single and triple bonds structure. Nevertheless, the stability of C₁₈ is weak at room temperature in gas. Thus, it is difficult to study the spectrum, orbital, and bonds characters of the C₁₈ molecule in the experiment. In this paper, we have obtained absorption spectrum, orbital, and bonding characters of the C₁₈ molecule in theory. Besides, bonds and spectra of C₂₄O₆, C₂₂O₄, C₂₀O₂, B₉N₉, C₆, C₁₂, C₁₆, and C₂₀ molecules have been investigated to further confirm the structure and the characters of the C₁₈ molecule. The results show that carbon-carbon bonds of C₂₄O₆, C₂₂O₄, and C₂₀O₂ molecules in ring are alternating single and triple bonds except those connected with CO group. B₉N₉ molecule as the isoelectronic structure of C₁₈ has a larger bandgap and shorter wavelength of absorption spectra than those of the C₁₈ molecule. Moreover, all bonds between boron and nitrogen in B₉N₉ molecule are single one. Study bonding characters for C₆, C₁₂, C₁₆, and C₂₀ molecules have confirmed that carbon-carbon bonds of cyclo[n]carbon changed gradually from double bonds to alternating single and triple bonds with increasing n value. The data from theory would give help for future research on C₁₈ and B₉N₉ molecules in experiment.

Theoretical investigation for bond and spectra characters of cyclo[18]carbon (C₁₈), prepared with low-temperature STM-AFM (scanning tunneling microscopy-atomic force microscopy) from C₂₄O₆, C₂₂O₄, and C₂₀O₂ molecules, which have been confirmed being alternating single and triple bonds structure.

中文翻译：

---

sp-杂化环[18]碳（C18）键和光谱的理论研究。

在实验中，用低温STM-AFM（扫描隧道显微镜-原子力显微镜）从C ₂₄ O ₆，C ₂₂ O ₄和C ₂₀ O ₂分子制备的环[18]碳（C ₁₈）具有已经证实是交替的单键和三键结构。然而，C ₁₈在气体中在室温下的稳定性较弱。因此，在实验中难以研究C ₁₈分子的光谱，轨道和键的特性。在理论上，我们已经获得了C ₁₈分子的吸收光谱，轨道和键合特性。此外，C的键和光谱_研究了24 O ₆，C ₂₂ O ₄，C ₂₀ O ₂，B ₉ N ₉，C ₆，C ₁₂，C ₁₆和C ₂₀分子，以进一步证实C ₁₈分子的结构和特性。结果表明，环中的C ₂₄ O ₆，C ₂₂ O ₄和C ₂₀ O ₂分子的碳-碳键为交替的单键和三键，除了与CO基相连的键。B ₉ N ₉分子为C的等电子结构₁₈具有较大的带隙和比与C的吸收光谱的较短波长₁₈分子。此外，B ₉ N ₉分子中硼与氮之间的所有键均为单键。对C ₆，C ₁₂，C ₁₆和C ₂₀分子的键合特性研究表明，环[n]碳的碳-碳键随着n值的增加从双键逐渐变为交替的单键和三键。理论数据可为将来对C ₁₈和B ₉ N _9的研究提供帮助 实验中的分子。

低温STM-AFM（扫描隧道显微镜-原子力显微镜），C ₂₄ O ₆，C ₂₂ O ₄和C ₂₀ O制备的环[18]碳（C ₁₈）键和光谱特征的理论研究_2个分子，已确认是交替的单键和三键结构。