凡得瓦爾鍵結弱,預解離常見於凡得瓦爾分子光譜。振動預解離(Vibrational predissociation, VP)可用來研究凡得瓦爾分子內能量轉移。本論文研究C3Ar，?1u的振動能階~1560- 1679 cm-1的振動預解離產物分布，並試著從中歸納振動預解離的趨勢及分子內振動能重組路徑。 本實驗在超音速分子束中光解丙二烯產生C3，經由與惰性氣體之間的碰撞產生C3Ar凡得瓦爾分子。使用染料雷射與Nd:YAG雷射混頻的可調頻紫外雷射光偵測C3Ar，取得其在C_3 A ?-X ? 0 4^+ 0-0 0 0，0 8^- 0-0 0 0，與0 0 2-0 0 0躍遷附近的螢光激發光譜及螢光分光光譜。 從13個C3Ar上態的螢光分光光譜可知，大部分螢光來自C3Ar振動預解離所產生的C3。因振動預解離後?75% 能量轉為C3碎片的振動能，可視為V-V能量轉移;其振動預解離產物分布只有一半可以動量間隙定理(momentum gap law)預測。另外， C3角動量量子數改變|?P|及振動量子數改變|?v|的趨勢也被提出，它們可改變動量間隙定理預測的產物分布。約有一半能階的VP產物分布需要一新的模型。我們在此提出一高斯模型。從本論文碎片放光光譜可以重新估計出C3Ar X ?束縛能(binding energy)必須低於142 cm-1。 ;The van der Waals bond is generally weak, predissociation is often observed in the spectrum of van der Waals molecule. Its vibrational predissociation (VP) could be used to study the energy redistribution within the complex. In this study, the VP products of the ?1u state of the C3Ar levels with vibrational energies of 1560- 1679 cm-1 were investigated in an attempt to obtain the VP propensity rules and the intramolecular vibrational relaxation pathways. The C3Ar van der Waals complexes were stabilized by three-body collisions of Ar, the carrier gas atom, and C3 near the nozzle tip of a supersonic expansion, where the C3 molecule was produced by photolyzing allene by a 193 nm laser light. The complexes were optically excited by a tunable UV laser light by mixing the output of a dye laser and the fundamental of a Nd: YAG laser. The excitation spectra and emission spectra of C3Ar associated with C_3 A ?-X ? 0 8^- 0-0 0 0, 0 4^+ 0-0 0 0, and 0 0 2-0 0 0 bands were recorded and studied. Results from the emission spectra of 13 upper states of C_3 Ar show that most of the fluorescence came from the vibrationally excited C3 fragments by VP processes. Since more than 75% of the excitation energies were remained in the vibration motion of the C3 fragment, these VP processes are considered as the V-V type energy transfer. About half of the obtained branching ratios of the VP products can be fit with a model based upon the momentum gap law. |?v|- and |?P|-propensity rules are also found; they can alter the predictions derived from the momentum gap law. At the other half levels, the branching ratios of their VP products require a new model; a Gaussian function was proposed. The binding energy of the ground electronic state of C3Ar is estimated at ?142 cm-1 from emission spectra obtained in this work.
