| 摘要(英) |
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 Ã1u 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. |
| 參考文獻 |
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