EXPERIMENTS OF WATER FORMATION ON WARM SILICATES
EXPERIMENTS OF WATER FORMATION ON WARM SILICATES
复制标题
温硅酸盐成水实验
DOI：
10.1088/0004-637x/788/1/50
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
G. Vidali
中科院分区：
文献类型：
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作者：
Jiao He;G. Vidali
当尘埃颗粒的温度高于它们在稠密云中的温度时，当H、H2和O2在颗粒上的停留时间可以忽略不计时，水的形成仍然应该是可能的，通过OH的氢化和Eley-R理想类型的反应。我们测定了非晶态硅酸盐表面的脱附能至少为143 meV(1656K)。这比之前星际介质化学模型中使用的值高出400K，可能高达410meV(4760K)。这将水在颗粒上有效形成的温度范围从大约30K扩大到至少50K，甚至可能超过100K。我们没有发现水分子在形成时离开表面的证据。相反，通过程序升温脱附实验，我们发现在160K左右无定形硅酸盐的表面形成了水。我们还测量了50K下H和D与无定形硅酸盐表面的一层O_3反应的截面，σH=1.6±0.27 ？2和σD=0.94±0.09 ？2分别小于O_3分子的尺寸，这表明该反应机制比热原子更可能是埃利-R理想的。通过这些实验获得的信息应该有助于理论家评估水在热颗粒上形成的相对贡献与在气相中的贡献。
When dust grains have a higher temperature than they would have in dense clouds, and when H, H2, and O2 have a negligible residence time on grains, the formation of water should still be possible via the hydrogenation of OH and Eley–Rideal-type reactions. We determined that the OH desorption energy from an amorphous silicate surface is at least 143 meV (1656 K). This is 400 K higher than the value previously used in chemical models of the interstellar medium and is possibly as high as 410 meV (4760 K). This extends the temperature range for the efficient formation of water on grains from about 30 K to at least 50 K, and possibly over 100 K. We do not find evidence that water molecules leave the surface upon formation. Instead, through a thermal programmed desorption experiment, we find that water formed on the surface of an amorphous silicate desorbs at around 160 K. We also measured the cross-sections for the reaction of H and D with an O3 layer on an amorphous silicate surface at 50 K. The values of the cross-sections, σH = 1.6 ± 0.27 Å2 and σD = 0.94 ± 0.09 Å2, respectively, are smaller than the size of an O3 molecule, suggesting the reaction mechanism is more likely Eley–Rideal than hot-atom. Information obtained through these experiments should help theorists evaluate the relative contribution of water formation on warm grains versus in the gas phase.
影响因子：
3.2
作者：
Y. Sekine;H. Imanaka;T. Matsui;B. Khare;E. Bakes;Christopher P. McKay;S. Sugita
通讯作者：
Y. Sekine;H. Imanaka;T. Matsui;B. Khare;E. Bakes;Christopher P. McKay;S. Sugita
10 K 量子隧道表面反应 OH + H2 → H2O+ H 的实验研究
DOI：
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发表时间：
2013
期刊：
影响因子：
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作者：
E. Ohtani;S. Kamada;T. Sakai;H. Terasaki;Y. Shibazaki;T. Sakamaki;S. Takahashi;T. Sakairi;H. Fukui;A. Q. Baron;Y. Oba;田中亮吉;Y. Oba
通讯作者：
Y. Oba