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USNDP

18Ne (95TI07)


(See Energy Level Diagrams for 18Ne)

GENERAL: See Tables 18.35 [General Table] (in PDF or PS) and 18.36 [Table of Energy Levels] (in PDF or PS).

For B(E2) of 18Ne*(1.89) and other parameters see (87RA01) and Table 2 in the Introduction.

1. 18Ne(β+)18F Qm = 4.446

The half-life of 18Ne is 1672 ± 8 ms: see (78AJ03) and (83AD03). The decay is primarily to 18F*(0, 1.04, 1.70 MeV). In addition there is an extremely weak branch [(2.07 ± 0.28) x 10-3%] to 18F* (1.08 MeV) [Jπ = 0-; T = 0] (83AD03): see Table 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 (83AD03). It has been proposed as a probe of T-odd nuclear forces (92HE12). See also (82HE04). For the earlier work see (83AJ01, 87AJ02).

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

This reaction was studied at 6He angles from 0° to 10° with a magnetic spectrometer (92HAZZ). 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 (87WI11) using information from the isobaric analog 18O. A new 18Ne level at Ex = 6.15 MeV (see 16O(3He, n)) has been observed (90GAZW) which may play a role in 14O + α burning. See also (88CA1N).

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 (88FU02, 89FU01).

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

See Table 18.38 (in PDF or PS). See also (83AJ01). Recent work reported in (91GA03) found that the 3+ level in 18Ne predicted by (88WI08) 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 (90GAZW). [See discussion under 14O(α, γ)18Ne.] See also (89GAZW, 90GAZR). For applied work related to this reaction see (91GU05, 92DI04).

6. 16O(α, nn)18Ne Qm = -23.773

See (91GU05) 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 (83AJ01)). See also (83OS07).

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

Measurements at E(12C) = 480 MeV are reported in (88KR11, 88ME10). 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 (83AJ01)] and at 48.3 MeV (85AL15; to 18Neg.s.) and 100 to 292 MeV (85SE08; to 18Neg.s.). The excitation functions for production of 18Ne*(0, 1.89) have been measured for E(π+) = 80 to 292 MeV: see (83AJ01, 85SE08). See also (87AJ02).

The behavior of double charge exchange (DCX) cross sections at low energies (50 ± 30 MeV) was reviewed in (87PA1H, 88SE1A, 89BA1R). See also the review of (89ST1H). Measurements at energies of 300 - 500 MeV above the Δ(1232) resonance were reported in (89WI02). More recently a search for an η bound state in this reaction is described in (92JOZZ, 93JO03).

The contribution of the two-nucleon pion absorption emission mechanism is discussed in (90CH14). See also (89CH1O, 90CH1U) and see (89YU1A). A quark-antiquark annihilation mechanism is proposed in (89CH21). A two-amplitude model for the DCX energy dependence is described in (89FO02). In other recent work, the contribution of sequential charge exchange and δ-nucleon charge exchange is examined in (93GI03). Absorption contributions near Tπ = 50 MeV are evaluated by (92OS05). High energy DCX and isovector renormalization is calculated and compared with data in (93OS01). See also (92MA46) for a discussion of dibaryon effects.

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

Observed triton groups are displayed in Table 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 (81NE09).

11. 20Ne(3He, nα)18Ne Qm = -7.926

See (91GU05).