About Calculator X-Mass

Calculator X-Mass is a tool designed to help scientists prepare samples for X-ray Absorption Fine Structure (XAFS) experiments. It determines the ideal sample and diluent mass required to achieve a perfect absorption edge step, which is critical for collecting high-quality data in transmission mode.

The calculations are based on the standard "Edge Step Method" and use atomic scattering factors (f2) to determine the mass attenuation coefficients for any given material and energy.

Calculation Method

The mass is calculated to achieve a specific jump in absorption (`Δμt`) at the element's edge. The required mass per unit area is computed to provide the target edge step (`Δμd`):

m/A = Δμd / (Δ(μ/ρ)_elem × f)

where `f` is the mass fraction of the element and `Δ(μ/ρ)elem` is the change in its absorption across the edge.

Explanation of Terms

• Δμt (or Δμd) — Target Edge Step
  The desired jump in absorption at the edge. A value of 1.0 is standard for good signal-to-noise. This is the primary target for the calculation.
• m/A — mass per unit area
  The amount of sample (in g/cm²) needed to achieve the target edge step.
• f — mass fraction of the element
  The weight fraction of the element of interest in the compound (e.g., Fe fraction in Fe₂O₃ is ~0.70).
• Δ(μ/ρ)_elem — elemental absorption change
  The change in the mass attenuation coefficient (cm²/g) of the element of interest across its absorption edge.
• μt — Total Absorption
  An informational value showing the total absorption of the sample at the edge energy. For concentrated samples, this will be higher than the edge step.