Meyer M, Cubaynes D, Glijer D, Dardis J, Hayden P, Hough P, Richardson V, Kennedy E T, Costello J T, Radcliffe P, Düsterer S, Azima A, Li W B, Redlin H, Feldhaus J, Taïeb R, Maquet A, Grum-Grzhimailo A N, Gryzlova E V, Strakhova S I
LIXAM, UMR 8624, CNRS-Université Paris Sud, Bâtiment 350, 91405 Orsay Cedex, France.
Phys Rev Lett. 2008 Nov 7;101(19):193002. doi: 10.1103/PhysRevLett.101.193002.
Two-color multiphoton ionization of atomic helium was investigated by combining extreme ultraviolet (XUV) radiation from the Free Electron Laser in Hamburg with an intense synchronized optical laser. In the photoelectron spectrum, lines associated with direct ionization and above-threshold ionization show strong variations of their amplitudes as a function of both the intensity of the optical dressing field and the relative orientation of the linear polarization vectors of the two fields. The polarization dependence provides direct insight into the symmetry of the outgoing electrons in above-threshold ionization. In the high field regime, the monochromaticity of the XUV radiation enables the unperturbed observation of nonlinear processes in the optical field.
通过将来自汉堡自由电子激光的极紫外（XUV）辐射与强同步光学激光相结合，对原子氦的双色多光子电离进行了研究。在光电子能谱中，与直接电离和阈上电离相关的谱线，其振幅随光学修饰场的强度以及两个场的线性偏振矢量的相对取向而呈现出强烈变化。偏振依赖性为阈上电离中出射电子的对称性提供了直接的洞察。在高场区域，XUV辐射的单色性使得能够在光场中无干扰地观察非线性过程。
