Vastel Charlotte, Phillips T G, Caselli P, Ceccarelli C, Pagani L
California Institute of Technology, Padasena, CA 91125, USA.
Philos Trans A Math Phys Eng Sci. 2006 Nov 15;364(1848):3081-90. doi: 10.1098/rsta.2006.1880.
Deuterium enhancement of monodeuterated species has been recognized for more than 30 years as a result of chemical fractionation that results from the difference in zero-point energies of deuterated and hydrogenated molecules. The key reaction is the deuteron exchange in the reaction between HD, the reservoir of deuterium in dark interstellar clouds, and the H3+ molecular ion, leading to the production of H2D+ molecule, and the low temperature in dark interstellar clouds favours this production. Furthermore, the presence of multiply deuterated species have incited our group to proceed further and consider the subsequent reaction of H2D+ with HD, leading to D2H+, which can further react with HD to produce D3+. In pre-stellar cores, where CO was found to be depleted, this production should be increased as CO would normally destroy H3+. The first model including D2H+ and D3+ predicted that these molecules should be as abundant as H2D+. The first detection of the D2H+ was made possible by the recent laboratory measurement for the frequency of the fundamental line of para-D2H+. Here, we present observations of H2D+ and D2H+ towards a sample of dark clouds and pre-stellar cores and show how the distribution of ortho-H2D+ (1(1,0)-1(1,1)) can trace the deuterium factory in pre-stellar cores. We also present how future instrumentation will improve our knowledge concerning the deuterium enhancement of H3+.
由于氘代和氢化分子零点能量的差异导致化学分馏，单氘代物种的氘增强现象已被认识超过30年。关键反应是HD（暗星际云中的氘库）与H3 +分子离子之间反应中的氘核交换，导致产生H2D +分子，而暗星际云中的低温有利于这种产生。此外，多重氘代物种的存在促使我们团队进一步研究，并考虑H2D +与HD的后续反应，生成D2H +，D2H +可进一步与HD反应生成D3 +。在原恒星核中，发现CO被耗尽，由于CO通常会破坏H3 +，这种生成应该会增加。第一个包含D2H +和D3 +的模型预测，这些分子应该与H2D +一样丰富。最近对仲-D2H +基态谱线频率的实验室测量使得首次检测到D2H +成为可能。在这里，我们展示了对一组暗云和原恒星核中H2D +和D2H +的观测，并展示了邻-H2D +（1(1,0)-1(1,1)）的分布如何追踪原恒星核中的氘工厂。我们还展示了未来的仪器将如何提高我们对H3 +氘增强的认识。
