Spectroscopic Studies of Unimolecular Reaction Dynamics of Vibronically State-selected Molecules

为了研究振动状态选择乙炔的振动动力学，各种光谱技术已经被应用。(1)乙炔的A^1A_u态的未分级nv_3'+v_4‘/v_6‘ （n=0,1,2,3）振动态的振动能级系统，可从X^1Σ_g^+态的v_3’态的选定旋转能级J ’得到。nv_3‘+v_6’和nv_3‘+v_4’态通过a轴和b轴科里奥利相互作用相互耦合。(2) 3v_3‘+v_6’态的旋转能级大部分分裂为两个或多个能级，而3v_3‘+v_4’态的旋转能级则为单个能级。溢出能级的荧光衰减显示弱磁场下的量子拍。这表明能级分裂是由S-T相互作用引起的。由于v_6‘在平面内，而v_4’在平面外，激励态的S-T相互作用发生在平面几何结构中。(3)应用h原子作用光谱研究了47000 ~ 50600 cm^<-1>范围内激发态下乙炔的预解离效率。在超过弯曲振动反转势垒（约48000 cm^<-1>）的状态下，预解离得到增强。

In order to investigate vibrational dynamics of vibronically state-selected acetylene, various spectroscopic techniques have been applied.(1) The rovibronic level system of the ungerade nv_3'+v_4'/v_6' (n=0,1,2,3) vibrational states in the A^1A_u state of acetylene which are accessible from the selected rotational level J" of the v_3" state in the X^1Σ_g^+ state. The nv_3'+v_6' and nv_3'+v_4' state are found to couple with each other by the a-and b-axis Coriolis interactions.(2) Most of rotational levels of the 3v_3'+v_6' state split into two or more levels, while those of the 3v_3'+v_4' state are single. The fluorescence decay from the spilit levels shows a quantum beat under a weak magnetic field. This indicates that the level splitting is attributable to the S-T interaction. Since the v_6' mode is in-plane while the v_4'is out-of-plane, the S-T interaction occurs in the planar geometry of the excited acetylene.(3) The H-atom action spectroscopy has been applied to investigate the predissociation efficiency of acetylene excited in the gerade vibrational states in the region of 47000〜50600 cm^<-1>. The predissociation is enhanced in the states exceeding the inversion barrier of the bending vibration which is located around 48000 cm^<-1>.