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# Calculating scatteing lengths for D_{2}O

Calculating SLD values for D_{2}O in a few steps:

- Open NIST tabular values

- Press on H and find the coherent scattering lenght (Coh b) for deuterium (D =
^{2}H), i.e. 6.671 fm (fm = femtometer).

- Go back to the periodic table and find the coherent scattering lenght (Coh b) for oxygen (O). This time, use the value for O (5.803 fm), which is for the average mix of isotopes of O. In this case, Coh b for O is the same as for
^{16}O, as O is on average 99.8%^{16}O (see the conc column). - The coherent scattering lenght for D
_{2}O is the sum: b = 2$\cdot$6.671 fm + 5.803 fm = 19.145 fm.