The ortho-para ratio of water vapor in comet P/Halley
The ortho-para ratio of water vapor in comet P/Halley
复制标题
P/哈雷彗星中水蒸气的邻位比
DOI：
10.1007/978-3-642-82971-0_76
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
H. Larson
中科院分区：
文献类型：
--
作者：
M. Mumma;H. Weaver;H. Larson
在彗星彗发中，正、仲水的丰度比是一个不变量，给出了热平衡时正、仲水的丰度比与温度的关系，并定义了核自旋温度。讨论了彗星冰的物理温度与核自旋温度之间的关系，并探讨了利用观测到的正-对比来推断彗核性质的前景。本文给出了哈雷彗星2.7 μm附近ν_3波段高分辨红外光谱的正-对位比。在UT 1985年12月24.1日，它是2.73±0.17，在UT 1986年3月22.7/26.7日，它是3.23± 0.37。误差估计包含一个相当大的主观成分的大气透射率，并可能会减少等待进一步建模。在67%的置信限下，近日点前的核自旋温度为35 K（+9 K，-5 K），近日点后的核自旋温度大于40 K。这两个数字是一致的模拟值的平衡温度的哈雷核在远日点（~47 K）。然而，在95%的置信限下，它们也与超过50 K的温度完全一致，对应于约3.0的邻-对位比。
The abundance ratio of ortho-H2O to para-H2O is shown to be an invariant in the cometary coma, its dependence on temperature in thermal equilibrium is given, and the nuclear-spin-temperature is defined. The relation between the physical temperature of the cometary ice and the nuclear-spin-temperature is discussed, and the prospects for using the observed ortho-para ratio to infer properties of the cometary nucleus are explored. The ortho-para ratio in Halley’s comet, derived from high resolution infrared spectra of theν3-band near 2.7 μm wavelength, is given. On UT 1985 December 24.1, it was 2.73±0.17, and on UT 1986 March 22.7/26.7, it was 3.23± 0.37. The error estimates contain a sizeable subjective component for atmospheric transmittance, and may be reduced pending further modelling. The nuclear-spin-temperature was 35 K (+9 K, −5 K) pre-perihelion, and >40 K post-perihelion, at the 67% confidence limit. Both numbers are consistent with modelled values of the equilibrium temperature of Halley’s nucleus at aphelion (~47 K). However, at the 95% confidence limit they are also fully consistent with temperatures exceeding 50 K, corresponding to an ortho-para ratio of ~3.0.