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18Ne (1995TI07)

(See Energy Level Diagrams for 18Ne)

GENERAL: See Table 3 preview 3 [Electromagnetic Transitions in A = 18-19] (in PDF or PS), Table 18.35 preview 18.35 [General Table] (in PDF or PS) and Table 18.36 preview 18.36 [Table of Energy Levels] (in PDF or PS).

For B(E2) of 18Ne*(1.89) and other parameters see (1987RA01) and Table 2 preview 2 in the Introduction.

1. 18Ne(β+)18F Qm = 4.446

The half-life of 18Ne is 1672 ± 8 ms: see (1978AJ03) and (1983AD03). The decay is primarily to 18F*(0, 1.04, 1.70 MeV). In addition there is an extremely weak branch [(2.07 ± 0.28) × 10-3%] to 18F* (1.08 MeV) [Jπ = 0-; T = 0] (1983AD03): see Table 18.33 preview 18.33 (in PDF or PS) for the parameters of the decay. The parity mixing in the 18F*(1.04, 1.08) 0+ - 0- doublet has been studied by (1983AD03). It has been proposed as a probe of T-odd nuclear forces (1992HE12). See also (1982HE04). For the earlier work see (1983AJ01, 1987AJ02).

2. 12C(12C, 6He)18Ne Qm = -22.913

This reaction was studied at 6He angles from 0° to 10° with a magnetic spectrometer (1992HAZZ). New levels at Ex > 6 MeV, including 18Ne*(6.15, 7.35 MeV), were found. Astrophysical implications are discussed.

3. 14O(α, γ)18Ne Qm = 5.112

The thermonuclear reaction rates for this reaction have been estimated (1987WI11) using information from the isobaric analog 18O. A new 18Ne level at Ex = 6.15 MeV (see 16O(3He, n)) has been observed (1990GAZW) which may play a role in 14O + α burning. See also (1988CA26).

4. 14O(α, p)17F Qm = 1.190

This reaction is considered important in the generation of Z ≥ 10 nuclei from products in the hot CNO cycle. Microscopic multichannel calculations for this reaction are discussed in (1988FU02, 1989FU01).

5. 16O(3He, n)18Ne Qm = -3.196

See Table 18.38 preview 18.38 (in PDF or PS). See also (1983AJ01).

Recent work reported in (1991GA03) found that the 3+ level in 18Ne predicted by (1988WI08) occurs at Ex = 4.561 ± 0.009 MeV. Astrophysical consequences are discussed. New levels in 18Ne at Ex ≥ 6 MeV observed in 16O(3He, n) were reported in (1990GAZW). [See discussion under 14O(α, γ)18Ne.] See also (1989GAZW, 1990GAZR). For applied work related to this reaction see (1991GU05, 1992DI04).

6. 16O(α, nn)18Ne Qm = -23.773

See (1991GU05) for measurements at Eα = 40 MeV.

7. 16O(10B, 8Li)18Ne Qm = -18.951

At E(10B) = 100 MeV, the angular distribution to 18Ne*(3.38) [(d5/2)24+ state], which is preferentially populated, has been studied. 18Ne*(1.89) is also observed (see (1983AJ01)). See also (1983OS07).

8. 16O(12C, 10Be)18Ne Qm = -22.663

Measurements at E(12C) = 480 MeV are reported in (1988KR11, 1988ME10). The 4+ level at Ex = 3.38 MeV is observed.

9. 18O(π+, π-)18Ne Qm = -6.101

Angular distributions have been studied at E(π+) = 164 and 292 MeV [see (1983AJ01)] and at 48.3 MeV (1985AL15; to 18Neg.s.) and 100 to 292 MeV (1985SE08; to 18Neg.s.). The excitation functions for production of 18Ne*(0, 1.89) have been measured for E(π+) = 80 to 292 MeV: see (1983AJ01, 1985SE08). See also (1987AJ02).

The behavior of double charge exchange (DCX) cross sections at low energies (50 ± 30 MeV) was reviewed in (1987PA1H, 1988SE1A, 1989BA1R). See also the review of (1989ST1H). Measurements at energies of 300 - 500 MeV above the Δ(1232) resonance were reported in (1989WI02). More recently a search for an η bound state in this reaction is described in (1992JOZZ, 1993JO03).

The contribution of the two-nucleon pion absorption emission mechanism is discussed in (1990CH14). See also (1989CH1O, 1990CH1U) and see (1989YU1A). A quark-antiquark annihilation mechanism is proposed in (1989CH21). A two-amplitude model for the DCX energy dependence is described in (1989FO02). In other recent work, the contribution of sequential charge exchange and δ-nucleon charge exchange is examined in (1993GI03). Absorption contributions near Tπ = 50 MeV are evaluated by (1992OS05). High energy DCX and isovector renormalization is calculated and compared with data in (1993OS01). See also (1992MA46) for a discussion of dibaryon effects.

10. 20Ne(p, t)18Ne Qm = -20.022

Observed triton groups are displayed in Table 18.38 preview 18.38 (in PDF or PS) as are Jπ derived from DWBA analysis of angular distributions: The 0+3 state, identified at Ex = 4.59 MeV, appears to have a largely s21/2 configuration based on its large downward shift with respect to the analog state in 18O (1981NE09).

11. 20Ne(3He, nα)18Ne Qm = -7.926

See (1991GU05).