Measurement of reflectance by gas ionization.

Area of Science:

• Physics
• Materials Science
• Spectroscopy

Background:

• Accurate reflectance measurements are crucial for characterizing materials, particularly under challenging conditions like high vapor pressure.
• Traditional methods can be limited by sample volatility and photoelectric effects.

Purpose of the Study:

• To develop and validate a new double ionization chamber technique for precise reflectance determination.
• To overcome limitations in measuring reflectance from high vapor pressure samples.

Main Methods:

• Utilizing a double ionization chamber to measure photon beam ionization before and after sample reflection.
• Employing a novel electrometer-ratiometer to compare ionization signals.
• Applying a 20V potential to the sample to mitigate photoelectric current interference up to 26 eV photon energies.

Main Results:

• The current ratio within the ionization chambers declines exponentially with pressure (100-5000 microm).
• Extrapolation of the data to zero pressure accurately yields sample reflectance.
• A reflectance of 12.47% at 841 Å was measured for an evaporated gold film using air as the filling gas.

Conclusions:

• The developed double ionization chamber method offers improved accuracy for reflectance measurements.
• This technique is particularly effective for high vapor pressure samples.
• The method provides a reliable approach for material characterization through reflectance analysis.