Observations of D/H ratios in H2O, HCl, and HF on Venus and new DCl and DF line strengths☆
Observations of D/H ratios in H2O, HCl, and HF on Venus and new DCl and DF line strengths☆
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金星上H2O、HCl、HF中的D/H比观测以及新的DCl、DF线强度☆
DOI：
10.1016/j.icarus.2013.02.010
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发表时间：
2013
期刊：
影响因子：
3.2
通讯作者：
L. Rothman
中科院分区：
文献类型：
--
作者：
V. Krasnopolsky;D. Belyaev;I. Gordon;Gang Li;L. Rothman
使用半经验偶极矩函数计算了D35 Cl和DF的基本带中的谱线强度，该偶极矩函数来自H35 Cl和HF的振转谱线强度的最准确和精确的测量。以这种方式获得的氘代物质的值是上级的任何可用的测量或计算数据的日期。我们对金星上H2O、HCl和HF的D/H比的研究是基于NASA IRTF的CSHELL摄谱仪进行的空间分辨高分辨率光谱学。在金星上使用R5（1-0）线在3024.054cm− 1搜索DF，结果DF混合比为0.23±0.11ppb，相当于标准平均海水（SMOW）中的（D/H）HF=420±200倍。金星上的H2O丰度是用3022.366和3025.761cm− 1的线反演的，这两条线是在0.3pr. mm的异常低的架空大地含水量下观测到的。与2722 cm −1附近的HDO同时观测相比，这导致（D/H）H2O=95±15倍SMOW。对2141.540cm−1处D35 Cl R4（1-0）谱线观测的再分析（Krasnopolsky，V.A. [2012年b]。Icarus 219，244-249）使用改进的谱线强度和更彻底的光谱平均给出（D/H）HCl=190±50倍SMOW。在74公里处测得的（D/H）H2O=95±15与De Bergh等人观测到的120±40（De Bergh，C.，Bezard，B.，欧文，T.，Crisp，D.，Maillard，J.P.，Lutz，B.L. [1991年]。Science 251，547-549）从地面到中间层，云下有利于恒定的（D/H）H_2 O，这与理论预测雅阁。D/H 100消除了Krasnopolsky观测中H2O丰度之间的2倍差异（Krasnopolsky，V.A. [2010年b]。Icarus 209，314-322）和金星快车最低点观测（Cottini，V.，Ignatiev，N.I.，Piccioni，G.，Drossart，P.，Grassi，D.，Markiewicz，W. J.[2012年]。伊卡洛斯217，561-569）。在我们的观测中，HDO和H2O谱线的等效宽度是相似的;因此，它们的比值中的一些误差被抵消了。HCl在中间层中的光化学作用倾向于使D富集在HCl中，并使其耗尽在H2O中。这可以解释在HCl和H2O中观察到的D/H之间的双重差异。另一种解释是基于Bjoraker等人在中间层中观察到的（D/H）H2O 200（Bjoraker，G.L.，拉尔森，H. P.，妈妈M. J.蒂默曼河，Montani，J.L. [1992]。公牛。上午。Soc.24，995）和Fedorova等人（Fedorova，A.等J. Geophys. Res. 113，E00 B22）。这意味着H2O和HCl之间的D有效交换，并且两种物质中的D/H几乎相等。然而，这需要从低层大气到中间层的D/H增加两倍。这种增加没有理论支持;此外，凝结过程通常会耗尽云层上方的D/H。HF的光化学尚未被研究过，它主要在低热层进行，HF中的D/H可能与H2O中的D/H非常不同。总的来说，金星上所有含氢物种的D/H观测数据有助于解决金星上氘分馏问题。
Intensities of the spectral lines in the fundamental bands of D35Cl and DF were calculated using the semi-empirical dipole moment functions derived from the most accurate and precise measurements of intensities of the ro-vibrational lines of H35Cl and HF. Values obtained in this way for the deuterated species are superior to any available measured or calculated data to date. Our study of the D/H ratios in H2O, HCl, and HF on Venus is based on spatially-resolved high-resolution spectroscopy using the CSHELL spectrograph at NASA IRTF. Search for DF on Venus using its R5 (1-0) line at 3024.054cm−1results in a DF mixing ratio of 0.23±0.11ppb that corresponds to (D/H)HF=420±200 times that in the Standard Mean Ocean Water (SMOW). H2O abundances on Venus were retrieved using lines at 3022.366 and 3025.761cm−1that were observed at an exceptionally low overhead telluric water abundance of 0.3pr.mm. The measured H2O mixing ratios at 74km vary insignificantly between 55°S and 55°N with a mean value of 3.2ppm. When compared with simultaneous observations of HDO near 2722cm−1, this results in (D/H)H2O=95±15 times SMOW. Reanalysis of the observation of the D35Cl R4 (1-0) line at 2141.540cm−1(Krasnopolsky, V.A. [2012b]. Icarus 219, 244–249) using the improved line strength and more thorough averaging of the spectra gives (D/H)HCl=190±50 times SMOW. The similarity of the measured (D/H)H2O=95±15 at 74km with 120±40 observed by De Bergh et al. (De Bergh, C., Bezard, B., Owen, T., Crisp, D., Maillard, J.P., Lutz, B.L. [1991]. Science 251, 547–549) below the clouds favors the constant (D/H)H2Ofrom the surface to the mesosphere, in accord with the prediction by theory. D/H≈100 removes a difference of a factor of 2 between H2O abundances in the observations by Krasnopolsky (Krasnopolsky, V.A. [2010b]. Icarus 209, 314–322) and the Venus Express nadir observations (Cottini, V., Ignatiev, N.I., Piccioni, G., Drossart, P., Grassi, D., Markiewicz, W.J. [2012]. Icarus 217, 561–569). Equivalent widths of the HDO and H2O lines are similar in our observations; therefore some errors cancel out in their ratios. Photochemistry of HCl in the mesosphere tends to enrich D in HCl and deplete it in H2O. This may be an explanation of the twofold difference between the observed D/H in HCl and H2O. An alternative explanation is based on (D/H)H2O≈200 observed in the mesosphere by Bjoraker et al. (Bjoraker, G.L., Larson, H.P., Mumma, M.J., Timmermann, R., Montani, J.L. [1992]. Bull. Am. Astron. Soc. 24, 995) and Fedorova et al. (Fedorova, A. et al. J. Geophys. Res. 113, E00B22). This means an effective exchange of D between H2O and HCl and almost equal D/H in both species. However, this requires a twofold increase in D/H from the lower atmosphere to the mesosphere. This increase is not supported by theory; furthermore, condensation processes usually deplete D/H above the clouds. Photochemistry of HF has not been studied; it proceeds mostly in the lower thermosphere, and D/H in HF may be very different from that in H2O. Overall, the observational data on D/H in all hydrogen-bearing species on Venus are helpful to solve the problem of deuterium fractionation on Venus.