The Resonance Scattering of Protons by Lithium

The scattering of protons by a thick target of lithium has been studied in the energy region 272-586 kev at an angle of 156°, with a ball counter. The number of counts per microcoulomb at 458 kev is 2.08 times its value at 408 kev, and at 487 kev it has dropped to 1.48 times the value at 408 kev. The energy at which the maximum slope of the thick target curve occurs is within five kev of the energy for the lithium gamma-ray resonance maximum. The fact that the scattering from a beryllium crystal increased smoothly with proton energy throughout the region, showed that the resonance effect is not a peculiarity of the counter. This scattering anomaly indicates: (1) that the gamma-radiation obtained when ${\mathrm{Li}}^7$ is bombarded with 440-kev protons arises from a virtual level of ${\mathrm{Be}}^8$; (2) that the ${\mathrm{Be}}^8$ state is odd; and (3) that there are no odd excited states of the alpha-particle below approximately 13 Mev.