Self-Referenced Coherent Diffraction X-Ray Movie of Ångstrom- and Femtosecond-Scale Atomic Motion

Area of Science:

• Chemical Physics
• Molecular Dynamics
• X-ray Science

Background:

• Understanding ultrafast molecular dynamics is crucial for controlling chemical reactions.
• Previous methods lacked the spatial and temporal resolution to observe atomic motion in real-time.
• Laser-induced excitation provides a means to initiate molecular motion.

Purpose of the Study:

• To develop and demonstrate a novel technique for imaging intramolecular motion with high fidelity.
• To achieve femtosecond and ångstrom-scale resolution in observing atomic movements within molecules.
• To visualize the dynamics of molecular dissociation and rotation.

Main Methods:

• Utilized time-resolved femtosecond X-ray diffraction (TR-FXD) on laser-excited molecular iodine.
• Employed X-ray interference, using the initial charge distribution as a local oscillator for heterodyne amplification.
• Retrieved real-space movies of atomic motion from diffraction patterns.

Main Results:

• Successfully generated movies of intramolecular motion with 30 fs temporal and 0.3 Å spatial resolution.
• Observed coherent vibrational motion, dissociation, and rotational dephasing in molecular iodine.
• Demonstrated the high sensitivity and fidelity of the heterodyne X-ray interference method for molecular imaging.

Conclusions:

• The novel heterodyne X-ray interference technique provides unprecedented insight into ultrafast molecular dynamics.
• This method opens new avenues for studying chemical reactions and molecular processes at the atomic level.
• The observed phenomena highlight the complex dynamics occurring during molecular excitation and dissociation.