Study on optically forbidden excited states by photodetachment threshold electron spectroscopy

由于对称性选择规则和自旋守恒等限制，存在光学上禁止从基态进入的激发态。(1)氯分子的离子对态：通过B^3II(0^+_)态的光学-光学双共振识别了由于Franck-Condon限制而不能从基态进入的0^+_(^3P_0)态。0^-_(^3P_1)态也是通过A^3II(1_U)-B‘^3II(0^-_)相互作用态通过微扰促进的光学双共振获得的。确定了这些激发态的势函数。(2)NO_3自由基的电子激发态：利用组合差分从红外吸收带确定了^2A_2基态的分子常数。对称性…在红外区发现了更多的禁忌激发态(^2e“)。利用塞曼调制，光谱被指定为平行跃迁到^2A“_1振动态，其中e”振动通过激发态中的振动相互作用打破了Born-Oppenheimer近似。(3)HOCl的电子激发态：当我们光解在平流层臭氧平衡中起重要作用的HOCI自由基时，OH碎片显示其速度沿266 nm处的光解光的电子矢量排列。该波长下的光吸收通过2^1a‘-1^1a’跃迁，其跃迁力矩平行于O-Cl轴。另一方面，在355 nm的光解中，OH碎片垂直于光解光的电子矢量排列，表明发生了1^1A“-1^1A‘的转变。因此，HOCl仅通过单重态激发态进行光解，这与HOBr光解离可以通过三重态发生这一事实相反。较少

There are the excited states which are optically forbidden to access from the ground state due to several restrictions, such as the symmetrical selection rules and the spin conservation. This study aimed to find these excited states by photodetachment threshold electron spectroscopy, and to elucidate their nature in combining with other spectroscopic techniques.(1)Ion-pair states of molecular chlorine : The 0^+_(^3P_0) states inaccessible from the ground states due to the Franck-Condon restriction was identified by optical-optical double resonance through the B^3II(0^+_) state.The 0^-_(^3P_1) state was also accessed through the A^3II(1_u)-B'^3II(0^-_) interacting states by perturbation-facilitated optical double resonance. The potential functions of these excited states were determined.(2)Electronically excited states of NO _3 radical : The molecular constants of the ^2A_2 ground stats are determined from the infrared absorption band using the combination differences.The symmetrically … More forbidden excited state (^2E") was found in the infrared region. using the Zeeman modulation, the specturm was assigned as the parallel transition to the ^2A"_1 vibronic state in which the e" vibration broke the Born-oppenheimer approximation through the vibronic interaction in the excited state.(3)Electronically excited states of HOCl : When we photodissociate the HOCI radical which is important in the stratospheric ozone balance, the OH fragment showed its velocity to be aligned along the electronic vector of the photolysis light at 266 nm. The photoabsorption at this wavelength proceeds through 2^1A'-1^1A' transition whose transition moment is parallel to the O-Cl axis. On the other hand, in the photolysis at 355nm, the OH fragments were aligned perpendicular to the electronic vector of photolysis light, indicating that the 1^1A"-1^1A'transition occurred. Consequently, HOCl is photodissociated only through the singlet excited states, which is in contrast with the fact that the photodissociation can occur through a triplet state in the case of HOBr. Less