Neutron scattering lengths of the isotopes of thulium,ytterbium and lutetium

Coherent neutron scattering lengths and total cross sections have been measured on samples of ordinary Tm, Yb and Lu and on isotopically enriched compounds. From the experimental data for 0.57 meV neutron energy the following data were obtained: the coherent scattering lengths (in fm) of the bound atoms¹⁶⁹Tm (7.07+0.03);¹⁷⁰Yb (6.8±0.1);¹⁷¹Yb (9.7±0.1);¹⁷²Yb (9.5±0.1);¹⁷³Yb (9.56±0.10);¹⁷⁴Yb (19.2±0.1);¹⁷⁶Yb (8.7± 0.1); Yb (12.41±0.03);¹⁷⁵Lu (7.28±0.09);¹⁷⁶Lu (6.3±0.2) and Lu (7.21±0.03); the thermal absorption cross sections (in barn) for¹⁶⁹Tm (100±2); Yb (34.8±0.8) and Lu (74±2). In combination with the resonance parameters the measured coherent scattering lengths allowed the determination of potential scattering radii R′ which are of particular interest for the permanently deformed and deformable nuclei in the rare-earth region.