Lin Kang, Eckart Sebastian, Hartung Alexander, Trabert Daniel, Fehre Kilian, Rist Jonas, Schmidt Lothar Ph H, Schöffler Markus S, Jahnke Till, Kunitski Maksim, Dörner Reinhard
Institut für Kernphysik, Goethe-Universität, Max-von-Laue-Str. 1, 60438 Frankfurt am Main, Germany.
State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China.
Sci Adv. 2022 Mar 25;8(12):eabn7386. doi: 10.1126/sciadv.abn7386.
The photoelectric effect describes the ejection of an electron upon absorption of one or several photons. The kinetic energy of this electron is determined by the photon energy reduced by the binding energy of the electron and, if strong laser fields are involved, by the ponderomotive potential in addition. It has therefore been widely taken for granted that for atoms and molecules, the photoelectron energy does not depend on the electron's emission direction, but theoretical studies have questioned this since 1990. Here, we provide experimental evidence that the energies of photoelectrons emitted against the light propagation direction are shifted toward higher values, while those electrons that are emitted along the light propagation direction are shifted to lower values. We attribute the energy shift to a nondipole contribution to the ponderomotive potential that is due to the interaction of the moving electrons with the incident photons.
光电效应描述了在吸收一个或几个光子后电子的射出。该电子的动能由光子能量减去电子的束缚能决定，并且如果涉及强激光场，还由有质动力势决定。因此，人们普遍认为对于原子和分子，光电子能量不依赖于电子的发射方向，但自1990年以来理论研究对此提出了质疑。在这里，我们提供了实验证据，即逆着光传播方向发射的光电子能量向更高值偏移，而沿着光传播方向发射的那些电子能量向更低值偏移。我们将这种能量偏移归因于有质动力势的非偶极贡献，这是由于运动电子与入射光子的相互作用所致。
