Ultrafast Probing of Core Hole Localization in N ₂

Abstract

Although valence electrons are clearly delocalized in molecular bonding frameworks, chemists and physicists have long debated the question of whether the core vacancy created in a homonuclear diatomic molecule by absorption of a single x-ray photon is localized on one atom or delocalized over both. We have been able to clarify this question with an experiment that uses Auger electron angular emission patterns from molecular nitrogen after inner-shell ionization as an ultrafast probe of hole localization. The experiment, along with the accompanying theory, shows that observation of symmetry breaking (localization) or preservation (delocalization) depends on how the quantum entangled Bell state created by Auger decay is detected by the measurement.

Strong-field control and spectroscopy of attosecond electron-hole dynamics in molecules

“…Again, the answer requires the analysis of the entanglement between the parent ion and the liberated electron (see ref. 27 for a similar example in the core-hole localization in N 2 ). The symmetry is broken by the direction of the electron escape, characterized by the final momentum p. Its angle relative to the molecular axis Shown is the degree of control over strong-field ionization amplitudes, as a function of molecular alignment angle ⌰: green and blue curves show control over electron detachment from ⌸ vs. ⌺ orbital, the red curve shows control over electron detachment from bonding (channel à ) vs. nonbonding (channel-X ) orbital.…”

Non-linear processes in the interaction of atoms and molecules with intense EUV and X-ray fields from SASE free electron lasers (FELs)

“…The study of atomic and molecular inner-shell photoionization with conventional xray sources allowed the investigation of single-photon absorption and the understanding of single core holes ionization [97,98]. These studies enabled a rich physics dominated by electron correlation phenomena.…”

Ionization of one- and three-dimensionally-oriented asymmetric-top molecules by intense circularly polarized femtosecond laser pulses

“…This is possible if ionization leads to fragmentation of the molecule and the electrons can be measured in coincidence with fragment ions recoiling in directions that directly reflect the molecular orientation at the moment of ionization, a condition often referred to as the axial recoil limit. Such coincidence methods have been applied successfully, predominantly to small molecules where synchrotron radiation removes an inner shell electron [6][7][8][9] but also to situations where valence electrons are removed by UV radiation [10][11][12].…”