Young-type interference in projectile-electron loss in energetic ion-molecule collisions

Probing Atomic ‘Quantum Grating’ by Collisions with Charged Particles

The wave function of an atom, which passed through a diffraction grating, is characterized by a regular space structure. Correspondingly, the interaction of another particle with this atom can be viewed as scattering on an ‘atomic quantum grating’ made of just a single atom. Probing this ‘grating’ by collisions with a charged projectile reveals few-body interference phenomena caused by the coherent contributions of its ‘slits’ to the transition amplitude (the superposition principle) and quantum entanglement of the particles involved. In particular, the spectra of electrons emitted from the atom in collisions with swift ions exhibit a pronounced interference pattern whose shape can be extremely sensitive to the collision velocity.

Imaging molecular geometry with electron momentum spectroscopy

Electron momentum spectroscopy is a unique tool for imaging orbital-specific electron density of molecule in momentum space. However, the molecular geometry information is usually veiled due to the single-centered character of momentum space wavefunction of molecular orbital (MO). Here we demonstrate the retrieval of interatomic distances from the multicenter interference effect revealed in the ratios of electron momentum profiles between two MOs with symmetric and anti-symmetric characters. A very sensitive dependence of the oscillation period on interatomic distance is observed, which is used to determine F-F distance in CF₄ and O-O distance in CO₂ with sub-Ångström precision. Thus, using one spectrometer, and in one measurement, the electron density distributions of MOs and the molecular geometry information can be obtained simultaneously. Our approach provides a new robust tool for imaging molecules with high precision and has potential to apply to ultrafast imaging of molecular dynamics if combined with ultrashort electron pulses in the future.

Streaking temporal double-slit interference by an orthogonal two-color laser field

We investigate electron momentum distributions from single ionization of Ar by two orthogonally polarized laser pulses of different color. The two-color scheme is used to experimentally control the interference between electron wave packets released at different times within one laser cycle. This intracycle interference pattern is typically hard to resolve in an experiment. With the two-color control scheme, these features become the dominant contribution to the electron momentum distribution. Furthermore, the second color can be used for streaking of the otherwise interfering wave packets establishing a which-way marker. Our investigation shows that the visibility of the interference fringes depends on the degree of the which-way information determined by the controllable phase between the two pulses.

Observation of the interference effect in vibrationally resolved electron momentum spectroscopy of H2

We report the first measurement on vibrationally resolved electron momentum spectroscopy of H2 by using a high-resolution (e, 2e) spectrometer. The vibrational-specific experimental momentum profiles have been obtained and shown to be in agreement with calculations of (e, 2e) ionization cross sections taking into account the vibrational wave functions. Distinct deviations from Franck-Condon predictions have been observed in vibrational ratios of cross sections, which can readily be ascribed to the Young-type two-center interference. Unlike previous (e, 2e) work, the present observation of an interference effect does not rely on the comparison with the one-center atomic cross section.