Interferences of Ultrashort Free Electron Wave Packets

Abstract

Interferences of free electron wave packets generated by a pair of identical, time-delayed, femtosecond laser pulses which ionize excited atomic potassium have been observed. Two different schemes are investigated: threshold electrons produced by one-photon ionization with parallel laser polarization and above threshold ionization electrons produced by a two-photon transition with crossed laser polarization. Our results show that the temporal coherence of light pulses is transferred to free electron wave packets, thus opening the door to a whole variety of exciting experiments.

Ultrafast Relaxation Dynamics Observed Through Time-Resolved Photoelectron Angular Distributions

“…(1) As the photoelectrons emitted are iso-energetic, the two PE waves will interfere with each other. This interference may manifest itself as a modulation on the energy spectrum 31 or may alter the observed PADs. 27 The latter will depend on the relative phases and amplitudes of outgoing partial waves formed.…”

Attosecond electron wave packet interferometry

“…For example, electrons ionized by a strong laser field have been used to probe molecular structure 8 and molecular ground-state wavefunctions 7 . The new idea put forward in our work is to make use of interferences between continuum electron wave packets 9 that are prepared by a sequence of attosecond laser pulses. This allows us to probe the dynamics of continuum electrons in an infrared (IR) laser field, to investigate the fundamental process of atomic photoionization and to characterize the electronic wave packet created in the process.…”

Strong field quantum control by selective population of dressed states

“…At a delay time of 0.25T B later, the fast photoelectrons are enhanced and show more pronounced interference fringes, whereas the slow photoelectrons are reduced in intensity. The fringe spacing of h/τ corresponding to 45 meV (cf figure 2 at 0.25T B ) is determined by the delay τ between the pulses [47]. The photoelectron spectrum at 0.5T B is very similar to the reference spectrum.…”

“…The photoelectron spectrum depicted in figure 3(e) shows an AT splitting of E = 0.16 eV in agreement with the maximum splitting of the dressed states (ε u −ε l ) shown in figure 3(d). In addition, both AT components show interference fringes with an energy spacing of h/τ which are explained in terms of the final state interference of free electron wavepackets [47]. An alternative interpretation on the basis of the Young double-slit experiment is presented in section 4.3.…”

“…If the second laser pulse ionizes the equally populated dressed states similar to the first pulse ( figure 4(b)), we no longer know whether the electrons are produced during the first or the second laser pulse. Therefore, both AT components show interference fringes due to the final state interference of evolving free electron wavepackets [47]. In the experimental photoelectron spectrum ( figure 2 at 0T B ) the fringes in the fast photoelectrons are visible, whereas the fringes are not resolved in the low energy part of the photoelectron spectrum.…”