Magnetic Dichroism in the Two- and Three-Photon Ionization of Polarized Lithium

Symmetry breaks and shifts in the angular distributions of electrons emitted in ionization due to intense femtosecond laser fields have proven to provide detailed insights into the atomic break-up dynamics and timing. Prominent examples are “attoclock” experiments where ionization by elliptically polarized light is studied. Shifts in the photoelectron angular distributions are then interpreted in terms of tunneling time. In this contribution, we report on a similar phenomenon that arises in the few-photon ionization of excited and polarized atoms by linearly polarized light. A lithium target is prepared in the 2p (m_l=+1) state and exposed to femtosecond laser pulses with tunable center wavelengths ranging from 665 nm to 800 nm. Depending on the wavelength, the angular distributions feature strong shifts with respect to the laser polarization direction. These observations are interpreted in terms of interfering partial waves with asymmetric m-distributions.