Field-free molecular alignment for studies using x-ray pulses from a synchrotron radiation source

Area of Science:

• Physical Chemistry
• Atomic, Molecular, and Optical Physics
• X-ray Science

Background:

• Intense laser pulses can induce temporary spatial alignment in molecules.
• This molecular alignment could be leveraged for advanced X-ray-based experiments.

Purpose of the Study:

• To theoretically investigate the use of impulsive molecular alignment for X-ray experiments.
• To compare alignment dynamics using different laser pulse durations (10 ps vs. 95 ps).

Main Methods:

• Utilized a linear rigid rotor model for molecular systems of increasing size.
• Employed both quantum density matrix formalism and classical ensemble methods.
• Calculated alignment dynamics and compared outcomes for different laser pulse durations.

Main Results:

• The degree of molecular alignment increases with molecular size, confirmed by both quantum and classical methods.
• Sufficient alignment is achieved for resonant X-ray absorption with current 100 ps X-ray pulses.
• Shorter X-ray pulses (≤1 ps) are necessary for structural studies using elastic X-ray scattering.

Conclusions:

• Impulsive molecular alignment is a viable technique for X-ray spectroscopy.
• Future structural X-ray scattering experiments require ultrashort (≤1 ps) X-ray pulses to benefit from molecular alignment.