Absolute density-profile tomography of molecular beams using multiphoton ionization

Area of Science:

• Atomic and Molecular Physics
• Laser-Induced Processes
• Plasma Diagnostics

Background:

• Accurate measurement of molecular beam density is crucial for understanding gas dynamics and chemical reactions.
• Traditional methods often lack precision or require complex setups.
• Multiphoton ionization (MPI) offers a sensitive probe for atomic and molecular species.

Purpose of the Study:

• To present a novel, single-projection tomographic approach for absolute density measurement of rotationally symmetric molecular beams.
• To validate the technique using multiphoton ionization of a xenon beam.
• To simplify the reconstruction of absolute radial density profiles.

Main Methods:

• A single-projection tomographic technique utilizing multiphoton ionization (MPI).
• Requires knowledge of the laser beam's spatial intensity profile and ionization characteristics.
• Derivation of an analytic solution to the Abel transform for Gaussian projected density profiles.

Main Results:

• Successful tomographic reconstruction of a two-dimensional density profile for a xenon beam.
• Achieved a peak density measurement of (4.2+/-0.4)x10^18 m^-3.
• Results were compared favorably with theoretical predictions from the sudden freeze model.

Conclusions:

• The described MPI-based tomographic technique provides a simple and accurate method for absolute density measurements.
• The derived analytic solution simplifies the reconstruction of radial density.
• The technique is versatile and applicable to a wide range of atomic and molecular beams.