Alpha-Alpha Scattering at Low Energies
Oct 1, 195611 pages
Published in:
- Phys.Rev. 104 (1956) 123-134
Citations per year
Abstract: (APS)
We have measured the differential cross section for the scattering of alpha particles in helium between laboratory angles of 10 and 80 degrees and in the energy range 150 kev to 3 Mev, using He+ ions from our electrostatic generators. Below 400 kev no nuclear interaction occurs within the accuracy of the experiments (±1%), and Mott's formula for the Coulomb scattering of identical zero-spin particles is verified in detail. Above 400 kev the nuclear s-wave interaction begins to contribute, starting at a phase shift K0 near π, and smoothly decreasing with increasing energy to about 128 degrees at 3 Mev. Starting at 2.5 Mev, a small d-wave phase shift, K2 is found necessary to account for the observed angular distributions, reaching a value of 2.5 degrees at 3 Mev. Absolute values of the cross sections were determined by fitting the relative angular distributions with the single parameter K0 below 2 Mev, and by comparison with Rutherford scattering in argon above 2 Mev. The phase shift analysis was facilitated by a simple mechanical monograph described in Appendix III. A careful survey of the low-energy region containing the ground state of Be8, and the absence of any measurable effect leads to a lower limit for the mean life of the ground state of Be8 of 2×10−16 sec. Combined with a recently established upper limit of 4×10−15 sec, this locates the lifetime to within a factor of twenty.References(24)
Figures(0)