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1037the only negative ion which has been identified in HC1 by previous workers is Cl~. Charge transfer would not be expected to play a significant role if this were the ion in our experiment. The observed value of 0.71 ±0.02 cm 2 /v-sec is to be contrasted with that of 0.88 expected if Eq. (14) is applicable. This suggests that an orientation-dependent R~* interaction is important in this case, so that the mobility should vary as T 1/6 . If, however, these forces averaged out, so that only the INTRODUCTION R ADIATIVE capture of neutrons by Li 7 leads to an unstable isotope, Li 8 , which decays with about a 0.9 sec half-life by emitting electrons with a maximum energy of 13 Mev. 1 The residual nucleus, Be 8 , further decays into two alpha particles in about 10~1 5 second. Since the spin and parity of the ground state of Li 8 are 2, even, 2 and the spin and parity of the ground state of Li 7 are f, odd, the excited state of Li 8 formed by s-wave neutron capture in Li 7 will decay to the ground state by electric dipole emission. Calculations of the cross section for this process have been made by Thomas 3 and his results predict a cross section which decreases smoothly with increasing neutron energy. However, a maximum in the capture cross section might be expected near 250 kev because of a resonance in the total cross section of Li 7 at this energy. 4 The 2.28-Mev state in Li 8 , which is responsible for this resonance, has spin 3 and even parity and may decay to the ground state by 1 W. F. Hornyak and T.

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