Persistent Ground-State Planar Alignment of Iodine Molecule through Resonant Excitation

Area of Science:

• Physical Chemistry
• Molecular Physics
• Laser Spectroscopy

Background:

• Molecular alignment is crucial for understanding and controlling chemical reactions.
• Previous methods often require cryogenic temperatures or complex experimental setups.
• Laser-induced alignment offers a pathway to manipulate molecular orientation.

Purpose of the Study:

• To demonstrate the generation of persistent planar molecular alignment.
• To investigate the dynamics of iodine (I_{2}) molecules under resonant femtosecond laser excitation.
• To understand the role of initial molecular orientation in laser-induced alignment.

Main Methods:

• Subjecting a warm gas sample of I_{2} molecules to a resonant femtosecond laser pulse.
• Optically probing the I_{2} molecules in their vibronic ground states.
• Analyzing the spatial distribution of molecular axes relative to the laser field direction.

Main Results:

• Observed persistent planar molecular alignment, where molecular axes delocalized near a plane.
• The alignment plane was orthogonal to the direction of the laser field.
• Demonstrated that resonant excitation preferentially affects molecules with specific initial orientations.

Conclusions:

• Femtosecond laser pulses can induce persistent planar alignment in warm molecular gases.
• The observed alignment is a result of one-photon resonant excitation.
• Initial molecular alignment along the laser field is a key factor in this phenomenon.