The composition of ices in comet C/1995 O1 (Hale-Bopp) from radio spectroscopy
The composition of ices in comet C/1995 O1 (Hale-Bopp) from radio spectroscopy
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通过射电光谱分析彗星 C/1995 O1（海尔-波普）中的冰成分
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发表时间：
2004
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影响因子：
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通讯作者：
D. Lis
中科院分区：
文献类型：
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作者：
J. Crovisier;D. Bockelée;P. Colom;N. Biver;D. Despois;D. Lis
通过对彗星的射电光谱观测，发现了22种以上的分子、自由基和离子，以及几种同位素，其中大多数是最近在彗星C/1996 B2（百武）和C/1995 O1（海尔-波普）中发现的。其中，有6种分子是首次在海尔-波普彗星的无线电波长光谱调查过程中探测到的（Bockelee-Morvan等人[CITE]），这次调查使用了CSO、IRAM 30米望远镜和Plateau de Bure干涉仪。此外，许多物种的搜索没有成功，其中一些物种的上限很严格。我们在这里提出了这些意见和进一步分析他们的结果的审查。这包括：（1）确定乙醛（CH_3CHO）的检出限，（2）确定乙烯酮（H_2CCO）或甲亚胺（CH_2NH）等小分子物质的检出限，（3）确定HC_5N/HC_3N、乙醇/甲醇、乙酸/甲酸等同系列物质的丰度比，（4）确定Na和HNC等关键彗星物质的前体物质;（v）对从水二聚体（H_2O）_2到甘氨酸等更奇异的物种的限制;（vi）H_2 ^（34）S同位素物种的探测和HDO和DCN的独立观测;（vii）对其他几种氘代物种的限制;（viii）对几种自由基和离子的限制以及对C_2H自由基的试探性探测;（ix）未识别谱线的存在。对于许多物种来说，相对于水，典型的丰度上限为2 - 5 x 10 ^（-4）。对于一些具有高偶极矩的线性分子，得到了更好的上限。但更复杂的分子，如二甲醚或甘氨酸，受到的约束很差。这些结果将为彗星冰的化学成分、彗星物质的形成机制以及内彗发中发生的化学过程提供重要线索。
From radio spectroscopic observations of comets, more than 22 molecules, radicals and ions, plus several isotopologues, were detected, the majority of them being recently revealed in comets C/1996 B2 (Hyakutake) and C/1995 O1 (Hale-Bopp). Among them, 6 molecules were detected for the first time (Bockelee-Morvan et al. [CITE]) in the course of a spectral survey conducted at radio wavelengths in comet Hale-Bopp with the CSO, the IRAM 30-m telescope and Plateau de Bure interferometer. In addition, many species were searched for unsuccessfully, some of them with stringent upper limits. We present here a review of these observations and further analysis of their results. This include: (i) confirmed detection of acetaldehyde (CH_3CHO); (ii) limits on small molecules such as ketene (H_2CCO) or methanimine (CH_2NH); (iii) limits on the abundance ratios in homologous series such as HC_5N/HC_3N, ethanol/methanol, acetic acid/formic acid; (iv) searches for precursors of key cometary species such as atomic Na and HNC; (v) constraints on more exotic species ranging from water dimer (H_2O)_2 to glycine; (vi) detection of the H_2^(34)S isotopic species and independent observations of HDO and DCN; (vii) limits on several other deuterated species; (viii) limits on several radicals and ions and a tentative detection of the C_2H radical; (ix) the presence of unidentified lines. Typical abundance upper limits of 2–5 x 10^(-4) relative to water are achieved for many species. Better upper limits are obtained for some linear molecules with high dipole moments. But more complex molecules such as dimethyl ether or glycine are poorly constrained. These results should give important clues to the chemical composition of cometary ices, to the formation mechanisms of cometary material, and to the chemical processes which occur in the inner coma.