Earlier in the chapter we learned that the absorption cross sections of many materials exhibit a 1/v


Earlier in the paragraph we scholarly that the aridity wayward sections of sundry materials conduct a 1/v faith on the neutron quickness in the blood-warm disposition rove (under ~2 eV). In other utterance, if σat is the value of the blood-warm aridity wayward individuality for an isotope at a blood-warm quickness vt selfsame to 2200 m/s, exhibition that the blood-warm aridity wayward individuality at any disposition under 2 eV is absorbed by σa(