School of Physical Sciences and NCPST, Dublin City University, Dublin 9, Ireland.
Phys Rev Lett. 2010 Jul 2;105(1):013001. doi: 10.1103/PhysRevLett.105.013001. Epub 2010 Jun 29.
We have observed the simultaneous inner-shell absorption of two extreme-ultraviolet photons by a Xe atom in an experiment performed at the short-wavelength free electron laser facility FLASH. Photoelectron spectroscopy permitted us to unambiguously identify a feature resulting from the ionization of a single electron of the 4d subshell of Xe by two photons each of energy (93±1) eV. The feature's intensity has a quadratic dependence on the pulse energy. The results are discussed and interpreted within the framework of recent results of ion spectroscopy experiments of Xe obtained at ultrahigh irradiance in the extreme-ultraviolet regime.
我们在 FLASH 短波长自由电子激光装置上进行的实验中观察到 Xe 原子同时内壳层吸收两个极紫外光子。光电子能谱使我们能够明确地识别出由 Xe 的 4d 亚壳层的单个电子被两个每个能量为（93±1）电子伏特的光子电离而产生的特征。该特征的强度与脉冲能量呈二次函数关系。结果在极紫外区超高辐照度下获得的 Xe 离子光谱实验的最新结果的框架内进行了讨论和解释。
