摘要：Small silicon-carbon clusters are important gas-phase constituents of stellar atmospheres, and are thought to play a role as potential seeds of the interstellar dusts formed in the envelopes of evolved carbon stars. Here we present the high-resolution optical spectra of the linear SiC2Si molecule (l-Si2C2) studied via laboratory experiments. Thel-Si2C2molecules are generated in a supersonically expanding planar plasma by discharging a silane-acetylene-argon gas mixture. The optical absorption spectra in the 5000−5300 Å region are recorded using sensitive pulsed cavity ring-down spectroscopy. In total, five optical absorption bands belonging to the$ \tilde{C} ^{3}\Sigma_{u} ^{-} $–$ \tilde{X} ^{3}\Sigma_{g} ^{-} $electronic transition system ofl-Si2C2are measured with fully resolved spin splitting fine structures in individual rotational transitions. Accurate spectroscopic constants for both$ \tilde{X} ^{3}\Sigma_{g} ^{-} $and$ \tilde{C} ^{3}\Sigma_{u} ^{-} $states ofl-Si2C2, including the spin-spin interaction constants and spin-rotation interaction constants, are determined from the experimental spectra, which can be used to simulate these optical bands with different temperatures. Using the determined spectroscopic constants, optical spectra ofl-Si2C2simulated with different rotational excitation temperatures are compared to the stellar spectra of evolved carbon stars V Hya and IRAS 12311−23509, where the triatomic SiC2are known to be abundant. Tentative assignments of thel-Si2C2spectral features in the stellar spectra are discussed.
关键词：enmolecular dataISM: moleculesISM: lines and bandsstars: carbon
