中国物理B ›› 2020, Vol. 29 ›› Issue (9): 93201-093201.doi: 10.1088/1674-1056/ab9431
Ya-Nan Sun(孙亚楠), Yan-Hui Wang(王艳辉), Le-Le Song(宋乐乐), Hai-Bin Du(杜海滨), Xiao-Chun Wang(王晓春), Lan-Lai He(赫兰海), Si-Zuo Luo(罗嗣佐), Qin Yang(杨钦), Jing Leng(冷静), Fu-Chun Liu(刘福春)
Ya-Nan Sun(孙亚楠)1,4, Yan-Hui Wang(王艳辉)2, Le-Le Song(宋乐乐)1,3, Hai-Bin Du(杜海滨)5, Xiao-Chun Wang(王晓春)1,4, Lan-Lai He(赫兰海)1,4, Si-Zuo Luo(罗嗣佐)1,4, Qin Yang(杨钦)1,4, Jing Leng(冷静)1,4, Fu-Chun Liu(刘福春)1,4
摘要: The ionization processes of NH3 molecule are studied by photoelectron velocity map imaging technique in a linearly polarized 400-nm femtosecond laser field. The two-dimensional photoelectron images from ammonia molecules under different laser intensities are obtained. In the slow electron region, the values of kinetic energy of photoelectrons corresponding to peaks 1, 2, 3, and 4 are 0.27, 0.86, 1.16, and 1.6 eV, respectively. With both the kinetic energy and angular distribution of photoelectrons from NH3 molecules, we can confirm that the two-photon excited intermediate Rydberg state is A~1 A2" (v2'=3) state for photoelectron peaks 2, 3, 4, and the three peaks are marked as 1223 (2 + 2), 1123 (2 + 2), and 1023 (2 + 2) multi-photon processes, respectively. Then, peak 1 is found by adding a hexapole between the source chamber and the detection chamber to realize the rotational state selection and beam focusing. Peak 1 is labeled as the 1323 (3 + 1) multi-photon process through the intermediate Rydberg state E~1A1'. The phenomena of channel switching are found in the slow electron kinetic energy distributions. Our calculations and experimental results indicate that the stretching vibrational mode of ammonia molecules varies with channels, while the umbrella vibration does not. In addition, we consider and discuss the ac-Stark effect in a strong laser field. Peaks 5 and 6 are marked as (2 + 2 + 1) and (2 + 2 + 2) above threshold ionization processes in the fast electron region.
中图分类号: (Multiphoton ionization and excitation to highly excited states)