Hyperfine-Structure-Induced Depolarization of Impulsively Aligned I_{2} Molecules

Area of Science:

• Molecular dynamics
• Quantum mechanics
• Laser spectroscopy

Background:

• Rotational wave packets in gas-phase molecules are typically studied for their revival structures.
• Previous observations did not account for complex substructures or decreasing mean alignment.

Purpose of the Study:

• To investigate the complex dynamics of rotational wave packets in I2 molecules.
• To explain the origin of nonperiodic substructures and decreasing mean alignment.

Main Methods:

• Generating rotational wave packets in I2 using a 450 fs laser pulse.
• Measuring time-dependent molecular alignment via Coulomb explosion imaging with a delayed probe pulse.
• Developing a quantum mechanical model incorporating electric quadrupole interaction.

Main Results:

• Observed characteristic revival structures alongside complex nonperiodic substructures.
• Measured a decreasing mean alignment, a novel phenomenon.
• The quantum model accurately reproduced the experimental alignment trace.

Conclusions:

• The complex dynamics arise from coupling between rotational angular momenta and nuclear spins via the electric quadrupole interaction.
• This study reveals new quantum phenomena in molecular rotational dynamics.
• Experimental and theoretical results show excellent agreement, validating the model.