Comparison of the l-Si₂C₂A–E bands (red dashed curves) with the reduced optical spectrum of IRAS 12311−3509 (see Lloyd Evans et al. 2000). The simulated spectra of SiC₂ and C₂ bands (thin black curves) are also plotted, with the 2, 2, and 3 bands of SiC₂ (a, b, and c, respectively). A rotational temperature of ∼300 K is used in the spectral simulations of l-Si₂C₂, SiC₂, and C₂. The peak postions of the l-Si₂C₂ band B and the C₂ (1, 1) Swan bandhead are indicated by vertical solid and dot lines, respectively.