Study on optically forbidden excited states by photodetachment threshold electron spectroscopy

由于对称选择规则和自旋守恒等限制，有些激发态在光学上是禁止从基态进入的。本研究旨在利用光剥离阈值电子能谱法寻找这些激发态，并结合其他光谱技术阐明它们的性质。(1)氯分子的离子对态：通过B^3II（0^+_）态，用光学-光学双共振识别了由于frank - condon限制而无法从基态进入的0^+_（^3P_0）态。通过微扰促进光学双共振，通过A^3II(1_u)-B'^3II（0^-_）相互作用态获得了0^-_（^3P_1）态。确定了这些激发态的势函数。(2) NO - 3自由基的电子激发态：利用组合差从红外吸收波段确定了NO - 3自由基的分子常数。在红外区发现了对称的更禁激发态（^2E"）。利用Zeeman调制，谱被指定为^2A“_1振动态的平行跃迁，其中e”振动通过激发态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片段的速度沿光解光的电子矢量在266 nm处排列。该波长的光吸收通过2^1A‘-1^1A’跃迁进行，跃迁力矩平行于O-Cl轴。另一方面，在355nm光解时，OH片段垂直于光解光的电子矢量排列，表明发生了1^1A”-1^1A”跃迁。因此，HOCl只能通过单重态激发态进行光解，而HOBr则可以通过三重态进行光解。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