Subnanosecond phase transition dynamics in laser-shocked iron.

Area of Science:

• Materials Science
• Condensed Matter Physics
• High-Pressure Physics

Background:

• Iron's sociotechnological and planetary importance necessitates understanding its structural transitions.
• Previous studies lacked detailed insights into iron's dynamic structural changes under extreme conditions.

Purpose of the Study:

• To investigate the subnanosecond structural dynamics of iron during compression and release.
• To identify the phase transitions and structural evolution of iron at high strain rates.

Main Methods:

• Utilized a combined short pulse optical laser and ultrashort free electron laser (FEL) pulse.
• Acquired high-quality X-ray diffraction data at 50-picosecond intervals up to 2500 picoseconds.

Main Results:

• Observed a three-wave structure during initial compression and a two-wave structure during decaying shock.
• Identified transitions involving alpha (α), gamma (γ), and epsilon (ε) iron phases.
• Detected negative lattice pressures and formation of expanded phases during rarefaction, followed by γ-phase recovery.

Conclusions:

• Provided unprecedented atomistic insights into iron's lattice compression and release dynamics.
• Demonstrated the capability to measure ultrafast structural evolution in materials.
• Advanced understanding of iron's behavior under extreme dynamic conditions.