Evaluation of incoherent scattering intensity by transmission and sample thickness

The H atom has a large incoherent scattering cross section and is a major source of incoherent scattering intensity, (dΣ/dΩ) inc , in small‐angle neutron scattering. By taking account of multiple scattering from H atoms, a useful method (the transmission method or T method) is proposed for the estimation of (dΣ/dΩ) inc for various types of hydrogen‐containing systems. The incoherent scattering intensity is calculated simply from the transmission, T , and the thickness of the sample, t , i.e. (dΣ/dΩ) inc ≅ [exp(Σ tot t ) − 1]/(4π t ) = (1 − T )/(4π t T ), where Σ tot ≡−(ln T )/ t is the macroscopic total cross section per unit volume. This method provides a reasonably accurate value of incoherent scattering intensity for various systems. The validity and the extent of applicability of the T method are examined for several samples, including light/heavy water mixtures, polymer gels and surfactant aqueous dispersions.