乙烯基~2A″电子态的振转分析

Ro-vibrational Analysis of the ~2A″ Electronic State of the Vinyl Radical

通过193nm光解丁烯酮分子产生乙烯基自由基(·C2H3).经射流冷却后,以另一束可调谐激光光解·C2H3,生成的氢原子碎片经共振增强多光子电离(REMPI)过程,记录氢离子信号随光解波长变化,得到21180￣21320cm-1范围内乙烯基A!2A″(!′5,6,8=1)←X!2A′(!″=0)跃迁的振转光谱.结合量化计算和光谱拟合,对该段光谱进行了细致的振转分析,确定了各振动谱带位置,识别了其中主要的转动跃迁.由光谱拟合得到各振动能级的预解离寿命,讨论了其与振动模式及激发转动量子数的依赖关系,证实了理论预测的乙烯基A!2A″电子态的面内解离机制.

Vinyl radical was generated by photolysing methyl vinyl ketone at 193 nm, then was photodissociated by another tunable laser in the 21180-21320 cm^-1 range. The dissociated H atom fragments were ionized and detected by resonance-enhanced multiphoton ionization （REMPI） processes. The ro-vibrational action spectra of the （A）^～^2A″（v′5,6,8=1）←（X）^～^2A′（v″=0） of vinyl radical were recorded by monitoring the H^＋ ion intensity with dissociation laser wavelength. The corresponding analyses were obtained with the aid of quantum chemical calculations and spectroscopic simulations, vibrational bands and main rotational transitions were definitely assigned. Additionally, the predissociative lifetime was derived from the simulated linewidth, and its dependence on the vibrational mode and rotational quantum number was discussed. The in-plane dissociation mechanism of the A^～^2A＂ state predicted by theoretical studies was confirmed.