Calculadora de Seção de Choque de Reação — Formula

Nuclear Reaction Cross Section

The macroscopic cross section combines the probability of a single nucleus interacting (microscopic cross section) with the number of target nuclei per volume.

Formulas

N = rho × NA / A (atom number density)

Sigma = N × sigma (macroscopic cross section)

Lambda = 1 / Sigma (mean free path)

where sigma is in barns (1 barn = 10⁻²⁴ cm²), NA = 6.022 × 10²³/mol.

Exemplo Resolvido

U-235 (sigma_f = 580 barns, density 19.1 g/cm³, A = 235).

  1. N = 19.1 × 6.022 × 10²³ / 235 = 4.89 × 10²² atoms/cm³
  2. Sigma = 4.89 × 10²² × 580 × 10⁻²⁴ = 28.38 cm⁻¹
  3. Mean free path = 1 / 28.38 = 0.0352 cm