Astronomical Detection of Rhomboidal S[CLC]i[/CLC]C[TINF]3[/TINF]

Abstract

Seven rotational transitions of SiC 3 , a planar, highly polar ring molecule, have been detected in the millimeter-wave band in the expanding envelope of the evolved carbon star IRC ϩ10216. On the assumption that SiC 3 has the same 40Љ diameter shell as SiCC, the mean column density of SiC 3 is cm . The rotational 12 Ϫ2 4.3 # 10 excitation of SiC 3 is similar to that of SiCC, with a low rotational temperature within the K-stacks of 10–20 K and a high rotational temperature across the K-stacks of roughly 50 K, which is probably close to the kinetic temperature of the shell.