The reaction 7Li(3He, p)9Be has been used to measure excitations and intrinsic widths of levels in 9Be below the 7Li + d threshold.Previously unreported levels have been found at excitations of (13.78 ± .03) MeV and (16.671 ± .008) MeV with widths of (590 ± 60) keV and (41 ± 4) keV respectively.Two overlapping levels have been found at (11.81 ± .02) MeV and (11.29 ± .03) MeV with widths of (400 ± 30) keV and (620 ± 70) keV respectively.Branching ratios from 9Be levels populated in this reaction to the ground and first excited states of 8Be have been measured by observing the associated protons in coincidence with the decay neutrons.Branching ratios were found to be:
Excitation in 9Be .... Branching Ratio.......... Final Nucleus.........
(MeV) .......................... (percent) .....................................
.. 2.43 ........................... 7.5 ± 1.5 .............. 8Be(g.s.)
.. 3.03 ........................... 87 ± 13......................................
.. 4.65 ........................... 13 ± 4.......................................
.. 6.76 .............................. ≤ 2 ......................................
.. 11.29 ...............................≤ 2 ......................................
.. 11.81 ...............................≤ 3 ......................................
..6.76 ........................... .41 ≤ B.R. ≤ .69 ....... 8Be(2+)
.. 11.29 ........................... 14 ± 4 .......................................
.. 11.81 ........................... 12 ± 4 .......................................
Corresponding reduced widths for neutron emission are calculated and a comparison of the results with the expectations of current nuclear models is made.In particular the measured branching ratio to 8Be(g.s.) from 9Be(2.43 MeV) corresponds to an f-wave reduced with θ2f = 2.1 x 10-2, in units of ħ2/mR2, with R = 4.35 fm.A comparison of this value with that predicted by a Nilsson model calculation, in which 9Be is taken to be a deformed nucleus, is discussed.The measured value for θ2f is found to be consistent with that expected on the basis of measured E2-transition rates between rotational levels in 9Be.
