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20Na (1998TI06)
(See Energy Level Diagrams for 20Na)
GENERAL: See 
20.32
[General Table] (in PDF or PS) and 
20.33
[Table of Energy Levels] (in PDF or PS) here.
| 1. 20Na(β+)20Ne | Qm = 13.887 |
20Na decays by positron emission to 20Ne*(1.63) and to
a number of other excited states of 20Ne: see 
20.31 (in PDF or PS) and reaction 59 in 20Ne. The
half-life of 20Na is 447.9 ± 2.3 ms [weighted mean of values quoted in (1978AJ03, 1983CL01, 1989CL02)]; Jπ = 2+: see (1987AJ02). See also (1992KUZO, 1992KUZQ) and (1993BL10; instrumentation).
The beta delayed alpha decay of 20Na has been studied by (1989CL02) [see reaction 2]. See also (1993XU06).
| 2. 12C(10B, nn)20Na | Qm = -10.936 |
Extensive measurements of the decay of 20Na nuclei produced in the 12C(10B, nn) reaction were reported by (1989CL02). Measurements included β+ spectra, β delayed alphas, βνα triple correlation coefficients, branching ratios, 20Ne level energies and the 20Na half-life. Isospin mixing and the weak-vector coupling constant were deduced.
| 3. 12C(14N, 6He)20Na | Qm = -21.576 |
An 82-MeV 14N beam was used by (1993BAZX) to study 20Na states up to Ex = 4.5 MeV. The cross section for the Ex = 2.646 MeV level was determined and the results suggest that state is not the mirror of the 1+ 3.173 MeV state in 20F as had been proposed. The results are consistent with the suggestion that the 2.646 MeV level is the mirror of the 2.966 MeV Jπ = 3+ state in 20F. See, however, reactions 5 and 8.
| 4. 19F(p, π-)20Na | Qm = -140.611 |
Angular distributions and analyzing powers have been studied at Ep = 199.6 MeV to 20Na*(0.74, 1.85, 3.01, 4.11) [probably unresolved]: it is suggested that the latter two have J = 6 or 7 (1987CA05).
| 5. 19Ne(p, γ)20Na | Qm = 2.195 |
The dominant process for the breakout from the HCNO cycle during hot
hydrogen burning in stars in considered to be
15O(α, γ)19Ne(p, γ)20Na
[see references in the following discussion]. Thus the 19Ne(p, γ)20Na reaction rate at stellar temperatures is of
considerable importance. The nuclear levels above the 19Ne(p, γ) threshold are critical for calculation of the reaction rates and
have been the object of several experimental studies by the
20Ne(3He, t) reaction (1988LAZY, 1989KU1D, 1989KU15, 1989SMZZ, 1990LA05, 1992SM03, 1995HO1G, 1995HO25, 1995GO16) as well as by
20Ne(p, n)20Na (1989KU15). See reactions 7, 8, 10 and 
20.35 (in PDF or PS).
The 20Na state at Ex = 2.646 MeV is presumed to be the strongest (p, γ) resonance and it has been the object of several studies [see refs. mentioned above as well as (1992GO10, 1992KU07, 1990DE34)]. See also (1995MI29). Work by (1993BAZX, 1993BR12, 1993CL09) strongly suggests that the state has Jπ = 3+ (the analog of the 20F 3+ state at Ex = 2.966 MeV) rather than 1+ as had been assumed in earlier work. More recent work described in (1994PA42, 1995HU13, 1995PA1K) determined a 90% confidence-level upper limit of 18 meV for the resonance strength of this level and provides arguments against the Jπ = 3+ assignment.
| 6. 19Ne(p, p)19Ne |
Resonances in 20Na above the proton threshold were studied
with radioactive 19Ne beams scattered off polyethelene targets
by (1994CO12). Analysis
by extended Breit Wigner, R-matrix and K-matrix formalism is described. Results are
summarized in 
20.34 (in PDF or PS).
| 7. 20Ne(p, n)20Na | Qm = -14.669 |
Early work on this reaction is described in (1987AJ02). More recently 20Na
levels up to Ex = 3.636 MeV were studied at Ep = 35 MeV by (1989KU15). See
20.35 (in PDF or PS).
The 20Ne(p, n) reaction at Ep = 136 MeV was used in measurements of Gamow-Teller strength (1991AN01) and in a study of isovector stretched-state excitation (1992TA04). A Δl = 2 angular distribution measured at Ep = 135 MeV (1995AN18) for the 20Na state at Ex = 2.645 MeV was determined to be consistent with Jπ = 3+.
A review of spin-isospin response in nuclei based on charge exchange reaction data is presented in (1989RA1G). See also (1987EL14). An analysis leading to total Gamow-Teller strength is described in (1988MA53).
| 8. 20Ne(3He, t)20Na | Qm = -13.906 |
Early work on this reaction is summarized in (1987AJ02). See also (1987EL14). More recent
measurements include those at E(3He) = 55.33 MeV (1988KU23, 1989KU15), at
E(3He) = 25.5 MeV (1988LAZY, 1990LA05), at
E(3He) = 29.7 MeV (1989SMZZ, 1992SM03) and at
E(3He) = 33.4 MeV (1990CL06, 1993CL09). Energy levels and
spin parity assignments obtained from these experiments are displayed in
20.35 (in PDF or PS). See also (1989AR1H, 1989KU1D). A major concern of this work
was the 20Na level at Ex = 2.645 MeV, which is presumed to be the
strongest (p, γ) resonance in 19Ne(p,
γ) [see reaction 5]. Detailed comparison of
data on 20Ne(3He, t)20Na and the analogue reaction
20Ne(t,
3He)20F by (1993BR12) and (1993CL09) has led to the
conclusion that the 2.645 MeV state in 20Na is to be identified with the
Jπ = 3+ state at Ex = 2.966
MeV in 20F. This conclusion is supported by the work of (1993BAZX) [see however the
discussion of reaction 5]. Measurements described in (1995HO1G, 1995HO25) have determined
the γ branching ratio for this state to be
Γγ/Γ ≈ 0.1. A
reanalysis by (1995GO16)
of earlier (3He, t) data has resolved conflicting values of excitation energies
for levels above the proton threshold.
| 9. 20Ne(12C, 12B)20Na | Qm = -27.256 |
A study of the response of nuclei to spin-isospin excitation displayed through charge exchange reactions such as 20Ne(12C, 12B)20Na is described in (1988RO17).
| 10. 20Mg(β+)20Na | Qm = 10.726 |
The 20Mg decay to 20Na has been studied through
β-delayed proton and γ-ray measurements. For the earlier work see (1979MO02, 1987AJ02). More recent studies are described
in (1992KU07, 1992GO10, 1993PIZZ, 1995PI03). Half-lives
measured for this decay are 95 ± 3 ms (1995PI03), 82 ± 4 ms
(1992GO10), 114 ± 17
ms (1992KU07),
95+80-50 ms (1979MO02). See 
20.36 (in PDF or PS) for β-decay
branching ratios and log ft values. A compilation of 20Na levels as
observed in beta decay and other experiments is provided in (1995PI03), and serves as the
basis for 20.33 (in PDF or PS) here.
| 11. 27Al(20Ne, 27Mg)20Na | Qm = -16.497 |
The Δ resonance is very strongly excited in this reaction at E(20Ne) = 950 MeV/A (1986BA16).