| 太阳原始星云原子团簇的初步研究 |
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| 引用本文： | 周瑶琪,张南.太阳原始星云原子团簇的初步研究[J].大地构造与成矿学,1994,18(1):85-95. |
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| 作者姓名： | 周瑶琪 张南 |
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| 摘 要： | 选用Ａｌｌｅｎｄｅ和宁强两块ＣＶ３陨石，在分子团簇串级飞行时间质谱装置上。用激光溅射模拟太阳原始星云在高能环境下的Ｓｉ－０，Ｆｅ－０和Ｍｇ－０原子团簇的形成和分布，对模拟过程所产上的原子团簇系列的结构和稳定性，以及可能的天体化学意义进行了初步探讨。
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| 关 键 词： | 太阳原始星云，原子团簇、CV3陨石 |
AN APPROACH OF THE ATOMIC CLUSTERS IN THE PREMITIVE SOLAR NEBULA |
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| Abstract: | he formation and distribution of Si-O, Fe-O, and Mg-O atomie clusters at a high energy environment of primitive solar nebula were studied by means of a simulation experiment of the laser ablation on two CV3 chondrites (Allende and Ningqing).A Time-of-Flight Maass Spectrometer (TOFMS) (Fig.V-1-1) was used in the simulation experiment.Because of the simple multiple relationship between mass of the four main elements,there are some troubes in the explanation of the mass peaks.In order to solve the problem,we adopted three supplementary measures:(a)compared with the negative ion TOFMS of the meteorite sample,because the clusters of Fe and Mg are difficult to produce negative ions in comparison with the clusters of Siand O; (b) compared with the result of experiments using samples containing only Si and O but not Fe and Mg.It would help us to underotand the distribution of the series of Si-O elusters;(c) we calculated theoritically the collision probability (P_K)among K atoms and the probability (P_1) of Fe_aMg_bSi_cO_d among the K atoms ceollision events in the Fe:Mg:Si:O=1:l:l:4 solar nebula system and in the Si:O=l:2 comparitive system.If the Pk×P1 of a certain cluster is too small,it can be considered that the cluster forms only a little or does not form at all. The atomie clusters appearing on the TOFMS are either of high structural stability,or has a large collison probability.The comprohesive explanation results of the TOFMS of some main atomie clusters produeed in the simulation experiments with Allende and Ningqiang are listed in Table V-l-2.From it we can see that the peaks with messes of 148,164,180,200,204,220,228,248 and 264 a.m.u. are elear. They are mainly the atomic clusters of Si-O and Fe-O. Among all these atomic clusters,Si3O4,Si3O6 and Fe3O2 clusters are the relatively most stable ones.Because no one bas ever studied oxide atomic clusters, especially the Si-O clusters,we developed an empirical rule:18-12-6 Electron Rule, which can be generalized as following:i, When the number of valence electrons in cluster is multiple of both 18 and 12 at the same time,the atomic cluster is the most stable;ii,Its total number of valence electrons being a muluple of 18, 12 and 6, the stability of the atomic cluster decreases successively.The theoritical background of the 18-12-6 Electron Rule is closely related with the nine atomic orbitals (one s + three p + five d) of each atom in its valence-shell.The molecular orbitals of the oxide cluster must be a multiple of 9.During the process of cluster formation,usually three atomie orbitals each atom are used for the formation of skeletal molecularr orbitals,and the others are oecupied by ligand bonding and nonbonding electrons.So the number of fulling the molecular orbitals of the oxide cluster is certainly a multiple of 2 x 9 (completely filled), 2 x (3+3)(the skeletal molecular orbitals are completely filled in the case of that the number of atoms of the cluster is even),and 2 x 3 (the skeletal molecular orbitals are completely filled in the case of that the number of atoms is odd). When the valence clectrons of the atomic cluster happens to the multiple of 6, 12, and 18, its stability will increase successively.Si-O clusters with higher stability produced in the simulation experiment are: Si_3O_4, Si_3O_5,Si_3O_6 and Si_3O_9,Their total valence electrons are 36, 42, 48 and 66, which are the multiple of 18, 6, 12 and 6 respectively.Among them the valence elcetrons of Si3O4 is a multiple of both 18 and 12 at the same time, hence it is most stable. The Fe-O elustero with relatively high stability produced in the simulation experiment are Fe_3O_2,F_e3O_4, Fe_3O_5 and Fe_3O_6, their valence electrons are the multiple of 18,12,6 and 12 respcetively. Among them the valcnce electrons of Fe_3O_2 is a multiple of both 18 and 12 at the same time, bence the stability of Fe_3O_2 is also the highest.The mass peak of Fe_3O_3 did not appear in the experinient, because its valence electrons is 42, neither multiple of 18 nor that of 12, so its stability is lower than that of other Fe-O clu |
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| Keywords: | premitive solar nebula atomic cluster CV3 chondrite TOFMS |
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