Double core-hole production in N2: beating the Auger clock.

Area of Science:

• Atomic and Molecular Physics
• Quantum Chemistry
• X-ray Science

Background:

• Core-hole spectroscopy is crucial for understanding molecular electronic structure.
• Creating multiple core holes simultaneously provides insights into electron correlation effects.
• Previous studies have explored single core-hole creation, but double core-hole states remain less understood.

Purpose of the Study:

• To investigate the sequential double K-shell hole creation in N2 molecules.
• To characterize the production and decay dynamics of these double core-hole states.
• To differentiate between two types of double core holes: on the same atom versus on different atoms.

Main Methods:

• Utilizing intense, ultrashort X-ray pulses from the Linac Coherent Light Source (LCLS) free electron laser.
• Employing time-resolved photoelectron spectroscopy and Auger electron spectroscopy.
• Comparing experimental results with theoretical calculations.

Main Results:

• Directly observed the creation of double K-shell holes on the same nitrogen atom in N2.
• Measured the production and decay pathways of these novel molecular states.
• Established an experimental upper limit for the contribution of double core holes on different nitrogen atoms.

Conclusions:

• The study provides the first direct experimental evidence for same-atom double core holes in a molecule.
• Results align well with theoretical predictions, validating models of core-hole interactions.
• Offers new insights into ultrafast electron dynamics and molecular fragmentation processes.