Table 1 The scattering properties of the helium isotopes in the solid and liquid states at a temperature of 1 K58,59

From: Density profile of 3He in a nanoscale 3He-4He superfluid film determined by neutron scattering

Isotope

b (fm)

Density (g/cm3)

nSLD (×10−6 Å−2)

3He @ 1K

5.74-1.483i

0.08172

0.9366

4He @ 1K

3.26

0.14511

0.7117

Solid 4He

3.26

0.187

0.9172

  1. b is the bound coherent scattering length in femtometres (fm)22. nSLD is the scattering length density defined as the product Nb where N is the number density of the material in question in atoms per Å319,22. Note the large imaginary component of b for 3He, indicating its large absorption cross section for neutrons, a feature that is absent for 4He. 4He and 3He scattering length densities as a function of temperature are presented in Supplementary Note 1.
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