Predissociation dynamics studied by degenerate four wave mixing spectroscopy

当通过NO分子的C-X双光子跃迁调谐激光频率时，在一个窄的固体角度内，近红外和紫外光辐射沿着激光传播方向发射。结果表明，紫外光是由参数四波混频(PFWM)过程产生。C-X带的激发光谱显示出良好的S/N比，这意味着脉冲宽度调制可以作为一种新的光谱方法来研究双光子共振能级。研究了NO的几个里德堡态的单转动能级的放大自发辐射。紫外光激光器固定在A态的特定旋转分量上。当共线引入第二束激光，并且频率与从A态到高里德堡原子的跃迁共振时，发现在近红外区沿激发光束产生了高方向性的ASE。弥散的ASE谱揭示了从初始填充能级到A态的级联辐射衰变。研究表明，ASE与弱的预解离竞争。

When then laser frequency was tuned through the C-X two-photon transition of NO molecules, near-IR and UV radiation were emitted along the laser propagation direction within a narrow solid angle. It was shown that the UV wave was generated by the parametric four wave mixing (PFWM) process. Excitation spectra for the C-X band exhibited an excellent S/N ratio, implying that PFWM might be utilized as a novel spectroscopic method which can interrogate the two-photon resonant levels.Amplified spontaneous emission (ASE) from single rotational levels of several Rydberg states of NO has been investigated. The UV laser is fixed to a specific rotational component of the A state. When the second laser was introduced collinearly and the frequency was resonant to the transitions fromthe A state to the higher Rydberg members, the highly directional ASE in the near IR region was found to be generated along the excitation laser beams. Dispersed ASE spectra revealed the cascading radiative decay from the initially populated level down to the A state. It was demonstrated that ASE competes with weak predissociation.