ADOPTED LEVELS for 4Li

Authors: J. H. Kelley, D. R. Tilley, H.R. Weller and G.M. Hale  Citation: Nucl. Physics A541 1 (1992)  Cutoff date: 8-OCT-1991

Full ENSDF file

S(n)= 1.14E4 keV SYS(p)= -3.10E3 keV 22
Reference: 2012WA38

References:
  A  3He(p,p) 

E(level)
(keV)
XREFJπ(level) T1/2(level)
     0.0A 2- % p = 100
   320A 1- 7.35 MeV
% p = 100
  2080A 0- 9.35 MeV
% p = 100
  2850A 1- 13.51 MeV
% p = 100
E(level): Level energies from an R-matrix calculation

Additional Level data and comments:

E(level)Comments
     0.0T=1, Γ=6.03 MEV
4.07 MeV above the p+3He mass.
E(level):
   320T=1
Strength is primarily 3p1.
E(level):
  2850T=1
Strength is primarily 1p1.
E(level):

General Comments:

The stability of 8B against particle decay into 4He+4Li, sets an upper limit of 1.7 MeV on the separation energy of 4Li into p+3He (1952Sh44). The instability of 4h against particle decay (discussion in 1992Ti02) makes the particle stability of 4Li very unlikely, since the Coulomb energy of 4Li is approximately 1.7 MeV larger than that of 4He (1963We10), and the nuclear energies should be identical because of charge symmetry. Indeed all decisive tests of the stability of 4Li have failed. Searches for its β decay have given negative results (discussion in 1992Ti02). Indirect proof of the non-existence of 4Li can be provided by a measurement of the solar neutrino flux which would be strongly influenced by the existence of 4Li. See 1968Me03. For other theoretical work on 4Li see 1979Hu02, 1981Ka39, 1988Co15.
The level structure of 4Li presented here is based on an R-matrix analysis (discussed in 1992Ti02) that gives a good representation of all the p+3He scattering data at proton energies below 20 MeV. Breit-Wigner resonance parameters from the analysis are given. The spin-correlation and 3He analyzing-power data included in the p-3He analysis determined that the lower 1- level is primarily in the 3p state, while the upper 1- is primarily in the 1p state, removing the ambiguities in the earlier phase-shift solutions, as was discussed in 1973Fi04.
As in the case of the 4h levels, which were based on the 4Li parameters, all the levels are at least 1 MeV lower than they were in 1973Fi04. The only significant difference between the 4h and 4Li levels is the position of the ground state above the nucleon-trinucleon threshold, as would be expected from the simple model used to obtain the 4h parameters. Again, the parameters predict very broad, positive- parity, t=1 states in the Eex=15-20 MeV range and antibound p-wave states that cannot yet be identified in the data. The known t=1 levels in the α=4 nuclei are summarized in the isobar diagram of 1992Ti02 fig.4.
The s-matrix poles resulting from the analysis are all far from the real axis with large decay widths, while their residues are relatively small, leading to small values of the strengths. Although the connection is not clear, the small residues for these poles may be connected with the anomalously small widths that have been observed in 1990Br14 and 1990Br17 that detect 4Li states in the particle spectra of breakup reactions. It may even be possible that these experiments are not detecting the 2- and 1- states as they assume, but positive parity states (0+ and 1+) whose s-matrix poles are much lower in energy than are the K(R)-matrix poles.
Q-value: Note: Current evaluation has used the following Q record