科研之友
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摘要
The partially deuterated linear isomer HDCCC of the ubiquitous cyclic carbene (c-C3H2) was observed in the starless cores TMC-1C and L1544 at 96.9 GHz, and a confirming line was observed in TMC-1 at 19.38 GHz. To aid the identification in these narrow line sources, four centimetre-wave rotational transitions (two in the previously reported K-a = 0 ladder and two new ones in the K-a = 1 ladder) and 23 transitions in the millimetre band between 96 and 272 GHz were measured in high-resolution laboratory spectra. Ten spectroscopic constants in a standard asymmetric top Hamiltonian allow the main transitions of astronomical interest in the K-a <= 3 rotational ladders to be calculated to within 0.1 km s(-1) in radial velocity up to 400 GHz. Conclusive identification of the two astronomical lines of HDCCC was provided by the VLSR, which is the same as for the normal isotopic species (H2CCC) in the three narrow line sources. In these sources, deuterium fractionation in singly substituted H2CCC (HDCCC/H2CCC similar to 4-19%) is comparable to that in c-C3H2 (c-C3H2/c-C3HD similar to 5-17%) and similarly in doubly deuterated c-C3H2 (c-C3D2/c-C3HD similar to 3-17%), implying that the efficiency of the deuteration processes in the H2CCC and c-C3H2 isomers are comparable in dark clouds.
- 出版日期2016-2
- 单位国家自然科学基金委员会
