Two-state wave packet for strong field-free molecular orientation

Area of Science:

• Molecular Physics
• Quantum Control
• Laser Spectroscopy

Background:

• Controlling molecular orientation is crucial for advanced applications.
• Achieving field-free orientation minimizes external influences.
• Carbonyl sulfide (COS) is a linear molecule suitable for rotational studies.

Purpose of the Study:

• To demonstrate strong laser-field-free orientation of ground-state carbonyl sulfide molecules.
• To investigate the role of laser pulse edges in creating rotational superpositions.
• To achieve a high degree of molecular orientation without a permanent external field.

Main Methods:

• Utilizing a 485-picosecond (ps)-long nonresonant laser pulse.
• Applying a weak static electric field to aid orientation.
• Creating a coherent superposition of two rotational states using laser pulse edges.

Main Results:

• Achieved strong transient molecular orientation with revivals after the laser pulse.
• Experimentally determined degree of orientation ⟨cosθ⟩≈0.6.
• Demonstrated that orientation can be achieved completely field-free by switching off the static electric field.

Conclusions:

• Strong laser-field-free molecular orientation is achievable in carbonyl sulfide.
• Transient revivals of orientation are driven by rotational state superposition.
• The method shows potential for precise, field-free molecular alignment and control.