A Search for Vibrationally Excited SiC2ν3= 1 toward IRC+10216

Five rotational transitions of vibrationally excited SiC 2 in the ν 3 = 1 antisymmetric mode were sought toward IRC+10216: 4 14 -3 13 , 5 15 -4 14 , 6 15 -5 14 , 7 17 -6 16 , and 7 35 -6 34 . All five spectra show emission features. However, the 5 15 -4 14 and 7 35 -6 34 transitions are noticeably lower in intensity compared to the other three. In addition, the 4 14 -3 13 , 6 15 -5 14 , and 7 17 -6 16 transitions have wider line widths than expected. For these reasons, we conclude that our detection of vibrationally excited SiC 2 is tentative. The ratio of column densities of vibrationally excited SiC 2 to ground state SiC 2 is N (ν 3 = 1)/ N (ν 3 = 0) ≲ 0.024.