Precision atomic beam density characterization by diode laser absorption spectroscopy.

Area of Science:

• Atomic Physics
• Laser Spectroscopy
• Beam Diagnostics

Background:

• Accurate measurement of atomic beam density is essential for fundamental physics research and applications.
• Existing methods for determining atomic beam density can be complex or lack precision.
• Development of simple, accurate, and broadly applicable techniques is needed.

Purpose of the Study:

• To present a straightforward experimental and theoretical method for determining absolute line-of-sight integrated atomic beam densities.
• To validate the technique's accuracy and precision using a thermal lithium beam.
• To demonstrate the method's sensitivity and applicability to low atomic densities.

Main Methods:

• Utilizing resonant laser absorption with a chopped atomic beam.
• Scanning laser frequency across the resonance transition and detecting absorption with a lock-in amplifier.
• Employing wavelength modulation spectroscopy for accuracy confirmation and a double laser beam technique for enhanced sensitivity.

Main Results:

• Achieved better than 5% accuracy and 3% precision for beams with ~1% absorption on a 1-second timescale.
• Demonstrated detection of fractional absorptions as low as 10^-5 on a 1-minute timescale using a double laser beam setup.
• Measured atomic densities as low as 5 × 10^4 atoms cm^-3 for a 9 mm thick lithium beam.

Conclusions:

• The developed resonant laser absorption technique offers a simple, accurate, and precise method for measuring atomic beam densities.
• The technique is highly sensitive, capable of detecting very low atomic densities.
• Its ease of implementation makes it suitable for a wide range of atomic and molecular beam experiments.