ADOPTED LEVELS for 4H
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 | Adopted Levels (PDF version)
| Q(β-)=2.220×104 keV 10 | S(n)= -1.60×103 keV 10 | ||||
| Reference: 2012WA38 |
| References: | |||
| A | 4He(π-,X) | B | 4He(n,p) |
| E(level) (keV) | XREF | Jπ(level) | T1/2(level) |
| 0.0 | A | 2- | % n = 100 |
| 310 | AB | 1- | 6.73 MeV % n = 100 |
| 2080 | 0- | 8.92 MeV % n = 100 | |
| 2830 | AB | 1- | 12.99 MeV % n = 100 |
E(level): Level energies from an R-matrix calculation
Additional Level Data and Comments:
| E(level) | Jπ(level) | T1/2(level) | Comments |
| 0.0 | 2- | % n = 100 | T=1, Γ=5.42 MEV 3.19 MeV above the N+3H mass. |
| 310 | 1- | 6.73 MeV % n = 100 | T=1 Strength is primarily 3p1. |
| 2830 | 1- | 12.99 MeV % n = 100 | T=1 Strength is primarily 1p1. |
The stability of the first excited state of 8Li against decay into decay into 4He+4H (1988Aj01) sets an upper limit for B(4H)|<3.53 MeV (see refs in 1992Ti02). This also sets a lower limit to the β- decay energy 4H-->4He of 17.06 MeV. The upper limit of the β- decay energy would be 20.60 MeV, if 4H is stable against decay into 3H+n. Estimates for the expected half-life of the β decay: if Jπ(4H)=0-, 1-, 2-, T1/2|>10 min; if Jπ (4H)=0+, 1+, T1/2|>0.03 s (see discussion in 1992Ti02). Experimentally there is no evidence for any β- decay of 4H, nor has particle stable 4H been observed. Evidence for a particle-unstable state of 4H has been obtained in 7Li(π-,t)3H+n at 8 MeV 3 above the unbound 3H+n mass with a width of 4 MeV. For other theoretical work see (1976Ja24, 1983Va31, 1985Ba39, 1988Go27).
The level structure presented here is obtained from a charge-symmetric reflection of the R-matrix parameters for 4Li after shifting all the p-3He E(|l) values by the internal Coulomb energy difference ΔE(Coulomb)=-0.86 MeV. The parameters then account well for measurements of the n-3H total cross section (1980Ph01) and coherent scattering length (1985Ra32), as is reported in (1990Ha23). The Breit-Wigner resonance parameters from that analysis for channel radius a(n-t)=4.9 fm are given. The levels are located substantially lower in energy than they were in the previous compilation (1973Fi04), as will be true for all the t=1 levels of the α=4 system. The 4Li analysis unambiguously determined the lower 1- level to be predominantly 3p1 and the upper one to be mainly 1p1; that order is preserved, of course, in the 4H levels. In addition to the given levels, the analysis predicts very broad positive-parity states at excitation energies in the range 14-22 MeV, having widths much greater than the excitation energy, as well as antibound p-wave states approximately 13 MeV below the 2- ground state. Parameters were not given for these states because there is no clear evidence for them in the data.
The structure given by the s-matrix poles is quite different, however. The p-wave resonances occur in a different order, and the positive-parity levels (especially for 0+ and 1+) are much narrower and lower in energy. It is possible that these differences in the s-matrix and K(R)-matrix pole structures, which are not yet fully understood, could explain the puzzling differences that occur when these resonances are observed in the spectra of multi-body final states.
Q-value: Note: Current evaluation has used the following Q record $ 23.51×103 11-2.91×103 11 1997Au07