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| molecules:ism:sic_2n_1 [2025/09/02 17:07] – mueller | molecules:ism:sic_2n_1 [2025/09/02 17:11] (current) – mueller |
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| //Astron. Astrophys.// **700**, Art. No. L20 (2025).\\ | //Astron. Astrophys.// **700**, Art. No. L20 (2025).\\ |
| Propadienediylidenesilylene and pentatetraenediylidenesilylene, which are also known as silatetratrienediylidene and silahexapentaenediylidene, respectively, were detercted in their <sup>3</sup>Σ<sup>−</sup> ground electronic states in the envelopes of the prototypical carbon-rich late-type AGB star CW Leonis in the course of a molecular line survey in the 31.0 to 50.3 GHz region carried out with the 40 m Yebes telescope. | Propadienediylidenesilylene and pentatetraenediylidenesilylene, which are also known as silatetratrienediylidene and silahexapentaenediylidene, respectively, were detercted in their <sup>3</sup>Σ<sup>−</sup> ground electronic states in the envelopes of the prototypical carbon-rich late-type AGB star CW Leonis in the course of a molecular line survey in the 31.0 to 50.3 GHz region carried out with the 40 m Yebes telescope. |
| In the case of propadienediylidenesilylene (SiC<sub>3</sub>), all three strong fine structure (FS) components with Δ//J// = Δ//N// of the four transitions with 5 ≤ //N// ≤ 9 were covered. Two FS components were heavily blended, the other ones unblended or partially blended, though the ones pertaining to the highest //N// have a rather modest signal-to-noise ratio. In the case of pentatetraenediylidenesilylene (SiC<sub>5</sub>), FS components of transitions with 16 ≤ //N// ≤ 25 were covered. While several of them are severely blended, sufficiently many are unblended or partially blended. The values of //T//<sub>rot</sub> were estimated as ~5 and ~17 K for SiC<sub>3</sub> and SiC<sub>5</sub>, respectively. The abundance ratios of the prolate rhomboidal (bicyclic) SiC<sub>3</sub> to the linear forms of SiC<sub>3</sub> and SiC<sub>5</sub> are about 4 : 2 : 1, where the value of the first species refers to a fit with two temperature components. \\ | In the case of propadienediylidenesilylene (SiC<sub>3</sub>), all three strong fine structure (FS) components with Δ//J// = Δ//N// of the four transitions with 5 ≤ //N// ≤ 9 were covered. Two FS components were heavily blended, the other ones unblended or partially blended, though the ones pertaining to the highest //N// have a rather modest signal-to-noise ratio. In the case of pentatetraenediylidenesilylene (SiC<sub>5</sub>), FS components of transitions with 16 ≤ //N// ≤ 25 were covered. While several of them are severely blended, sufficiently many are unblended or partially blended. The values of //T//<sub>rot</sub> were estimated as ~5 and ~17 K for SiC<sub>3</sub> and SiC<sub>5</sub>, respectively. The abundance ratios of the prolate rhomboidal (bicyclic) SiC<sub>3</sub> to the linear forms of SiC<sub>3</sub> and SiC<sub>5</sub> are roughly 4 : 2 : 1. Similar values are obtained if instead of rhomboidal SiC<sub>3</sub> (linear) SiC<sub>4</sub> is taken.\\ |
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