本篇論文主要藉由理論計算研究丙二烯雙聚體離子化後的反應。當實驗系統提供較低游離能量時，丙二烯雙聚體有兩個主要的反應機制，包含：異構化反應及氫解離反應。藉由Ab initio計算已可獲得m/z=80及79物種的結構及能量，並得到反應過程中的過渡狀態。而異構化反應的計算結果經由RRKM的計算可得到反應速率，因此可得到m/z=80物種的相對分佈。

The photodissociation of allene dimer in the region of low excess ionization energy has been investigated. In the low-energy region, there are two reaction channels, dissociation channel and isomerization channel, according to the experimental results. Using ab initio calculations, the structures and energies of the species m/z=80 and 79 have been determined, as well as the transition states of these reactions. The isomerization channel calculation results were used to evaluate the rate constants by RRKM theory. Hence the relative populations of species m/z=80 were obtained.

Ⅰ. Introduction1
Ⅰ.1 Introduction to ion-molecule reactions1
Ⅰ.2 Ion-molecule reactions in allene3
Ⅱ. Theory9
Ⅱ.1 ab initio quantum chemistry9
Ⅱ.2 RRKM theory13
Ⅲ. Results and Discussions25
Ⅲ.1 Neutral allene dimer25
Ⅲ.2 Ionic allene dimer32
Ⅲ.2.1 Vertical transition species32
Ⅲ.2.2 The species m/z=80 and 7934
Ⅲ.2.3 Rate constants of the isomerization and dissociation reactions38
Ⅳ. Conclusion99
Ⅴ. Acknowledgment100

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