High-resolution Doppler spectroscopy of light-dressed states of multi-electron molecules

为了阐明光修饰态在强激光场下多电子分子动力学中的作用，根据O~+碎片离子的动量成像图，研究了强激光场下O~(2+)+→O~++O在795 nm和398 nm激光波长下的离解过程。协方差图的测量是以高动量分辨率进行的，以安全地分配解离路径。从O~(2+)相对于激光偏振方向的各向异性动量分布来看，O_2~(2+)的电子态在解离过程中完全通过平行跃迁耦合。用四重态Π流形中O~(2+)的光修饰势能曲线的序列耦合模型解释了O~(2+)在795 nm和398 nm处的释放动能。观测到的光谱有多条谱线，其中大部分谱线归属于高电荷态碎片离子的电子跃迁，如N^+，N^&lt；2+&gt；，O^+和O^&lt；2+&gt；在409.24 nm处对NⅢ3^2P°→3^2S跃迁进行了高分辨率(~2 cm^~(-1))测量。当激光偏振指向光谱仪时，观察到的光谱呈现双重态，这是由于N^&lt；2+&gt；碎片离子通过N的库仑爆炸而被大量释放的动能的结果。根据由光谱分裂图案估计的动能，发现N^&lt；2+&gt；碎片是通过库仑爆炸过程产生的，NO^&lt；4+&gt；→N^&lt；2+&gt；+O^&lt；2+&gt；

In order to clarify the role of light-dressed states in the dynamics of a multielectron molecule in intense laser fields, the dissociation processes, O_2^+→O^++O, in intense laser fields (100fs, 〜3×10^<14> W/cm^2) are studied at the laser wavelength of 795 nm and 398 nm on the basis of the momentum imaging maps of the O^+ fragment ions. The covariance map measurements are performed with high momentum resolution to assign securely the dissociation pathways. From the anisotropic momentum distribution of O^+ with respect to the laser polarization direction, the electronic states of O_2^+ are found to be coupled exclusively through parallel transitions in the course of the dissociation process. The released kinetic-energy of O^+ for both 795 nm and 398 nm are interpreted consistently by a sequential coupling model of light-dressed potential curves of O_2^+ in the quartet Π- state manifold.The dispersed fluorescence spectra of NO and O_2 were measured in the spectral range between 300 nm and 700 nm using a spectrometer equipped with a intensified CCD camera. The observed spectra exhibits a number of spectral lines, most of which were assigned to the electronic transition of the higher charged fragment ions, such as N^+, N^<2+>, O^+ and O^<2+>. A high-resolution (〜2 cm^<-1> ) measurement was performed for the N III 3^2P°→3^2S transition at 409.24 nm. The observed spectra show a doublet pattern when the laser polarization is directed towards the spectrometer, which is interpreted as a result of a large released kinetic energy imposed on the N^<2+> fragment ion through the Coulomb explosion of NO.Based on the kinetic energy estimated from the split pattern of the spectra, it was found that the N^<2+> fragment was produced through the Coulomb explosion process, NO^<4+>→N^<2+>+O^<2+>.