(See Energy Level Diagrams for 20Ne)
GENERAL: See 3 [Electromagnetic Transitions in A = 20] (in PDF or PS), 20.16 [General Table] (in PDF or PS), 20.17 [Table of Energy Levels] (in PDF or PS) and 20.18 [Radiative decays in 20Ne] (in PDF or PS).
μ1.63 = 1.08 ± 0.08 nm (1989RA17).
B(E2)(↑) [0 → 1.63] = 0.0330 ± 0.0015 e2 · b2 (1978GR06). See also (1987RA01).
Intrinsic hexadecapole moment: Q4.25 = 0.022 ± 0.003 e2 · b2 (1978GR06).
μ4.25 = 0.52 ± 0.60 nm (1989RA17).
Isotopic abundance: (90.51 ± 0.09)% (1984DE53).
Observation of 20Ne in this reaction and measurement of the cross section was reported by (1990BEYY).
Excitation functions have been measured for E(10B) = 6 to 30 MeV (reaction (a)) and 6 to 20 MeV (reaction (b)). Large resonant structures are observed in reaction (b), particularly at Ex ≈ 38 MeV (α0) and 38.6 MeV (α to 16O* (7.0, 10.3, 16.2 (u)), Γ ≈ 0.6 MeV. See also (1983KAZF) and (1978AJ03). More recently, cross sections for fusion of 10B + 10B were measured for E(10B) = 1.5 - 5 MeV/nucleon, and evidence for fissionlike decay of 20Ne was observed (1989SZ01). Mass distributions from the sequential decay of the compound nucleus measured at E(10B) ≈ 110 MeV show no evidence for nuclear structure effects (1993SZ02).
Angular distributions of α-particles to many states of 20Ne below Ex = 10.7 MeV have been measured at E(14N) = 23.5 to 35 MeV. See also (1978AJ03, 1983AJ01). Numerical calculations of differential cross sections using CWBA and DWBA are reported by (1990OS1B).
At E(16O) = 19.5 to 42 MeV angular distributions for the 6Li ions corresponding to transitions to 20Ne*(0, 1.63, 4.25, 4.97, 5.62 + 5.79, 6.7 - 7.2) are in good agreement with Hauser-Feshbach calculations. See also (1978AJ03, 1985ST1B).
At E(11B) = 115 MeV, angular distributions are reported to 20Ne*(7.16, 8.78, 10.26, 11.95, 15.4). 20Ne*(8.78, 15.4, 17.3, 21.0 ± 0.07, 22.78 ± 0.06) are particularly strongly populated. It is suggested that these five states have Jπ = 6+, 7-, (8+), 9-, and 9-: see (1983AJ01).
At E(9Be) = 16 and 24 MeV, angular distributions have been measured for 20Ne*(7.3 ± 0.4, 9.2 ± 0.4, 10.9 ± 0.3, 12.2 ± 0.3, 15.7 ± 0.3): see (1983AJ01).
At E(12C) = 45 MeV the population of states of 20Ne with Ex = 8.46, 8.78, 9.03, 10.61, 10.67, 10.99, 11.01, 11.66, 11.94, 12.14, 12.39, 12.58, 12.73, 13.05, 13.17, 13.34 [7-], 13.69, 13.91, 14.29, 14.36, 14.81, 15.17 [6+], 15.38 [7-], 15.71 [(7,8)], 15.89[(7)], 16.16, 16.22, 16.51 [(8)], 16.73, 17.39 [9-], 18.18 and 18.32 MeV is reported (1976KL03). [Values in brackets are Jπ suggested on basis of Hauser-Feshbach calculations. The underlined states are well resolved: the authors indicate ± 20 keV for such states.] The relative intensities of the groups to 20Ne*(17.39, 15.38) [Jπ = 9-, 7-] argue against the existence of a superband: see (1978AJ03). See also (1983AJ01).
Double and triple (α, α, γ) correlations and γ-ray branching measurements [see 20.18 (in PDF or PS)] lead to the Jπ assignments shown in 20.19 (in PDF or PS). See 20.20 (in PDF or PS) for assignments to rotational bands. Angular distributions for many states have been reported at E(12C) = 4.9 to 51 MeV [see (1978AJ03, 1983AJ01, 1987AJ02)], at 5.2 to 5.8 MeV (1988BA12; α0), and at 69.5 MeV (1985XI1B). At E(12C) = 38 to 64 MeV, 20Ne*(7.17, 7.83, 8.54, 8.78, 9.03, 11.95, 12.13, 12.59, 13.90) are strongly populated and subsequently decay to 16Og.s. (1987RA02). Alpha decay of the Jπ = 6+ level at Ex = 15.16 MeV and the Jπ = 8+ level at Ex = 18.54 MeV to the first excited state of 16O was studied by (1992LA01). See 20.19 (in PDF or PS). For γ-decay measurements see (1987FI01), 20.19 (in PDF or PS) and (1978AJ03). Resonant characteristics of statistical fluctuations in 12C(12C, α)20Ne leading to the 12 lowest 20Ne states were studied by (1993GA02).
The yields of various groups of α-particles and their relevance to states of 24Mg, and fusion cross sections, have been studied by many groups: see (1978AJ03, 1983AJ01, 1987AJ02).
Sub-Coulomb cross sections calculated in a statistical framework are discussed in (1990KH05). A review of the state of theory and experiments on 12C + 12C reactions with formation of molecular states is presented in (1987DA1L).
See also (1987ER1B, 1988GO1G, 1988DE18, 1991SZ02).
Angular distributions of the 6Li ions to many states of 20Ne below 17.5 MeV have been reported for E(14N) = 30 to 78 MeV and E(12C) = 67.2 MeV. At the latter energy 20Ne*(16.67, 17.38, 18.11, 19.16, 19.6) are particularly strongly populated: see (1978AJ03). For reaction (b) to 20Neg.s. see the angular correlation measurements at E(14N) = 30 - 42 MeV reported by (1988AR24, 1994ZU03), and see the review of (1987GO12). An analysis of differential cross sections and angular correlation functions within a compound nuclear model is described in (1994BE55). Earlier work is cited in (1987AJ02). See also (1988BEYB, 1989BEXN, 1992ARZX).
Reaction (a) was studied at 150 MeV in a search for high-spin α-cluster resonances in 20Ne. A broad 10+ resonance was located at 27.5 MeV (1988AL07). See also (1988CAZV, 1994RA04).
Excitation functions in the range Ecm = 25.7 - 38.6 MeV were measured by (1993ES01). See also the comment (1993ZH21) and reply (1993ES03) on the work. Excitation functions for reaction (a) leading to members of the 20Ne ground state rotational band were measured for Ecm = 22 - 29 MeV by (1995SU06).
A triple coincidence measurement of reaction (b) through the 20Ne 6+ level at Ex = 8.78 MeV was reported by (1989WUZZ). α - α coincidence measurements by (1994KU18) at Ecm = 26.9 MeV were used to study the connection of highly deformed isomeric states in 28Si, 24Mg and 20Ne.
This reaction was studied with the use of molecular orbital theory (1988DI08).
For cross sections see (1986CU02).
See reaction 9.
For yields of 1.63 MeV γ-rays see (1982DE39).
Spectra were measured for E(20Ne) = 150 MeV/nucleon (1992EGZZ).
Observed resonances in the yield of capture γ-rays over the range Eα = 0.8 to 10 MeV are displayed in 20.21 (in PDF or PS). For a discussion of 20Ne*(11.26) [Jπ = 1+; T = 1], to which excitation by this reaction is parity forbidden, see (1983FI02). See also (1984BU01). Total cross sections have been measured in the range Ecm = 1.7 to 2.35 MeV. Assuming that S does not vary with energy over that interval, the astrophysical factor for non-resonant capture to 20Neg.s. is 0.26 ± 0.07 MeV · b. An estimate of 0.7 ± 0.3 MeV · b for S at 300 keV is deduced (1987HA24). A comment (1988BA26) on this work summarizes the status of theoretical descriptions of 16O(α, γ)20Ne and discusses the (1987HA24) result in the light of a microscopic calculation. See also 20.21 (in PDF or PS). For other papers on astrophysical considerations see (1985CA41, 1988CA26, 1990BL1K, 1991RA1C). For earlier work, see (1987AJ02).
A microscopic description of the α + 16O system in a multicluster model is discussed in (1994DU09). An anharmonic oscillating model description is presented in (1993CSZU).
For reaction (a) see (1990KOZG).
For reaction (b) see (1986KA36). A theoretical study of clustering in Yrast states is described in (1995KA53).
Excitation functions have been measured over a wide range of energies for elastically and inelastically scattered α-particles and γ-rays from the decay of 16O*(6.13, 6.92, 7.13) [see (1978AJ03, 1983AJ01)] and (1986LE23; 1.8 to 4.8 MeV; α0), (1985JA17; 2.0 to 3.6 MeV; α0), (1983CA1F, 1985CA09; 9.2 to 13.5 MeV; α0), (1992LA01; 10.2 to 18 MeV; α1) and (1979BI10, 1984RI06; 14.6 to 20.4 MeV; α0 → α5). See also (1983FR14, 1985ISZU) and 16O in (1993TI07).
A number of anomalies are observed: see 20.22 (in PDF or PS). Kπ parameter assignments derived from this and other work are displayed in 20.20 (in PDF or PS) (1984RI07). See also (1983MI22, 1990WE14, 1992AR18). Backscattering cross section measurements and other application-related studies are reported in (1990LE06, 1991LE33, 1992DE10, 1993CH48, 1993SO19). For reaction (b) see 12C in (1985AJ01).
In theoretical work related to 16O(α, α)16O, studies have been reported for: optical potentials in the range Eα = 0 - 150 MeV (1993AB02, 1995MI13), phase equivalent complex potentials (1996BA26), quadrupole resonances (1993BY03), a single-folding potential model (1993LI25, 1993YA08), an R-matrix analysis of elastic cross sections in the range Eα = 2 - 9 MeV (1994SH35), the orthogonality condition model (1987SA55), Yrast structure change of 20Ne (1987KA24), microscopic cluster theory (1987TA1C), core-plus-alpha states in terms of vibron models (1988CS01), distribution of α-particle strength (1988LE05), α cluster formation in the cluster-orbital shell model (1990HA38), the microscopic complex effective interaction for α - 16O (1991YA08), and the generator-coordinate description (1987RE04, 1992KR12).
Deuteron groups have been observed to many states of 20Ne: see 20.23 (in PDF or PS). Angular distributions have been measured for E(6Li) = 5.5 to 75.4 MeV: see (1978AJ03, 1983AJ01, 1984MO08). Measurements of angular diestribution at E(6Li) = 22 MeV provided data that were used to determine the ratios of α-particle widths in 19Ne relative to 20Ne (1995MA28) and to obtain alpha spectroscopic factors for 20Ne states up to Ex = 6 MeV (1996MA07). Angular correlations [(d, α0) to 16Og.s.] have been measured at E(6Li) = 60, 75, and 95 MeV (1982AR20, 1988ARZU). An experimental study of the competition between evaporation and direct transfer is described in (1995XE01). See also references cited in (1987AJ02).
In theoretical work published since the previous review, Hauser-Feshbach theory was applied to this reaction by (1987AR13), and angular distributions were analyzed with DWBA formalism by (1992RA22). See also (1994OS05).
States observed in this reaction are displayed in 20.23 (in PDF or PS). Angular distributions have been measured at E(7Li) = 15 to 68 MeV: see (1978AJ03, 1983AJ01). See also (1986CO15). The reaction 7Li(16O, t)20Ne was used in a lifetime measurement by (1995YU05).
Theoretical work related to this reaction includes studies on: the form of the α particle potential in direct α-transfer reactions (1986GR29, 1988GR1I), a Hauser Feshbach theory application (1987AR13), the optical potential (1989BE51), clustering phenomena and shell effects (1988RA1G), DWBA analysis (1992RA22).
Angular distributions in reaction (a) have been measured for E(16O) = 27.1 to 53.0 MeV and for E(12C) = 22.7 to 78 MeV [see (1978AJ03, 1983AJ01)] as well as at E(12C) = 109 MeV (1984MU04, 1985MU14; 20Ne*(1.63, 4.25, 5.79, 7.16, 8.78, 10.26, 11.95, 12.59, 15.34, 15.87, 17.30, 21.08, 22.87); σ(θ) at several angles; EFR-DWBA analysis). See also (1988CAZV). Γα0/Γ are displayed in 20.23 (in PDF or PS): see (1983AJ01, 1987AJ02) and (1983SH26). Spectroscopic factors were extracted in a direct reaction study reported by (1989OS02). Evidence for 10+ strength at Ex = 27.5 MeV is reported by (1988AL07). See also (1983DEZW). For discussion of 28Si states reached in this reaction see (1993ES01, 1993ES03, 1993ZH21). See also the discussion of instrumentation development for 8Be detection reported in (1991SU15). For reaction (b) see (1978AJ03) and (1986CA19). For reaction (c) and for a discussion of 24Mg states reached in this reaction see (1983SH26, 1984MU04). See also (1985BE37, 1986BE19, 1987SU03).
At E(13C) = 105 MeV angular distributions to 20Ne*(1.63, 4.25, 8.78, 11.95, 15.34, 21.0) have been studied by (1979BR03): the first four states are the 2+, 4+, 6+, and 8+ members of the 0+1 band; the two higher states [Jπ = 7-, 9-] belong to the 0- band for which the band head is 20Ne*(5.79). In addition, distributions are reported to 20Ne*(12.59, 15.9, 17.3) [Jπ = 6+, 8+, 8+] (1979BR03). See also (1985MU14). Spectroscopic factors were extracted in a direct reaction study reported by (1989OS02). For fusion cross sections see (1986PA10).
Angular distributions have been reported to a number of states of 20Ne at E(16O) = 23.9 to 95.2 MeV [see (1978AJ03, 1983AJ01)] and at E(16O) = 26, 28, and 30 MeV (1986CA24). (1983ME13) have studied the quasi-elastic spectrum at E(16O) = 50, 60, 68, and 72 MeV. Measurements of the energy dependence for E(16O) = 51 - 66 MeV were performed by (1996FR09). For excitation functions see (1986CA24; 20Ne*(0, 1.63)). See also (1982KO1C, 1984ME10, 1985ST1B, 1982KO1D, 1984AP03, 1984KO13).
Studies of the direct-reaction mechanism for this reaction have been carried out by (1988GA1L, 1988GA19, 1989OS02, 1990OS03). See also (1988AU03) and references cited in (1987AJ02).
The excitation function for α0 shows a resonance corresponding to 20Ne*(28.): see (1978AJ03). Measurements of Ay at E(3He) = 33 MeV, have been reported for the elastic scattering [reaction (a)] (1983LE03) and for many α-groups [see 16O in (1993TI07)] (1982KA12). For the earlier work and for other channels see (1983AJ01, 1987AJ02).
Neutron emission from this reaction was measured for Eα = 5.15 and 5.49 MeV by (1987SM09). Excitation functions were measured at astrophysical energies and S-factor curves were determined by (1995KU1H). See also work cited in (1978AJ03). In a recent theoretical study, the three-cluster generator coordinate method was applied to calculation of the low energy cross section by (1993DE32).
At E = 115 MeV the 8+ state at Ex = 11.95 MeV is strongly populated in both reactions: see (1983AJ01).
Angular distributions have been measured for E(3He) = 2.8 to 18.3 MeV. States of 20Ne observed in this reaction are displayed in 20.23 (in PDF or PS) of (1983AJ01). These include a state at Ex = 16.7329 ± 0.0027 MeV, Γcm = 2.0 ± 0.5 keV: Jπ = 0+, T = 2. Differential cross sections were measured at E(3He) = 30 MeV by (1995FUZT).
The previous review (1987AJ02), observed that over the range Ep = 2.9 to 12.8 MeV, the γ0 and γ1 yields are dominated by the E1 giant resonance (Γ ≈ 6 MeV) with the γ1 giant resonance displaced upward in energy. Strong well-correlated structures are observed with characteristic widths Γ ≈ 175 keV. Angular distributions taken over the energy range do not vary greatly with energy. They are incompatible with γ0 and γ1 coming from the same levels in 20Ne. The 90° γ0 yield for Ep = 3.5 to 10 MeV has been measured: the results are interpreted in terms of four primary doorway states at Ex = 16.7, 17.8, 19.1 and 20.2 MeV. See also (1985WAZV; Ep = 5.9 to 10.3 MeV; E2 strength; prelim.). See also (1986OUZZ).
More recently, polarized and unpolarized angular distributions were measured for Ep = 16.1 - 23.0 MeV (1988KU08). Data for (p, γ1) were also presented and a doorway state calculation was discussed. Cross section and analyzing powers for (p, γ0γ1) were measured in the range Ep = 3.5 - 13.3 MeV by (1988WA13) in a study of the E2 strength in 20Ne. See also the review of giant resonance work in (1988HA12).
The yield curve for 11.2 MeV γ-rays [from the decay of 20Ne*(11.26), Jπ = 1+, T = 1, to the ground state] displays a resonance at Ep = 4.090 ± 0.005 MeV [20Ne*(16.73)]. The 11.2 MeV γ-rays are isotropic which is consistent with the presumed 0+ character of this lowest T = 2 state in 20Ne: ΓpΓγ/Γ ≈ 0.5 eV. Since Γp/Γ (from the elastic scattering) is ≈ 0.1, Γγ ≈ 5 eV. For Ep = 5.65 to 6.21 MeV, the γ0 and γ1 yields are not resonant but the yield of 10.6 MeV γ-rays is resonant at 5.879 ± 0.007 MeV [Γcm = 9.5 ± 3 keV, Γp0Γγ/Γ ≈ 0.05 eV; Γγ ≈ 0.3 eV]. The 10.6 MeV γ-ray is due to the cascade decay of 20Ne*(18.43), Jπ = 2+, T = 2 via 20Ne*(12.22) to the 2+ state at 1.63 MeV. For the upper limits to the strengths of the transitions to various states of 20Ne from the 0+ and 2+ T = 2 states, see (1983AJ01). Internal pair conversion of the GDR at Ex ≈ 18 MeV was observed by (1989MOZY). Resonances observed in the capture reaction are displayed in 20.24 (in PDF or PS). For references see (1978AJ03, 1983AJ01). See also the astrophysics-related work in (1987RO25, 1988CA26). A study of absolute thick-target yields for elemental analysis at Ep = 7, 9 MeV is reported in (1987RA23).
The elastic scattering has been studied in the range Ep = 0.5 to 7.5 MeV and 24.9 to 46.3 MeV [see (1978AJ03)] and at Ep = 1.5 to 3.5 MeV (1985OU01, 1986OUZZ, 1986OU01). See also the measurements for Ep = 0.85 - 1.01 MeV at θ lab = 165° by (1989KN01), and the work reported in (1994CO12) in which a 19F radioactive beam was used in scattering off polyethelyne targets. The observed anomalies are displayed in 20.25 (in PDF or PS).
Resonances for inelastic scattering [p1 and p2] are listed in 20.26 (in PDF or PS). In general the resonances observed are identical with those reported from other 19F + p reactions, although the relative intensities differ greatly. Cross sections for production of 110 and 197 keV γ-rays are reported for Ep = 0.5 to 4.3 MeV by (1986CHYY). See also (1983LE28; astrophysics) and (1986BA88). For reaction (b) see (1986KA1U; applied) and 18F.
Observed resonances are displayed in 20.30 (in PDF or PS) of (1978AJ03). See also (1984BA1R, 1985CA41). The transfer polarization coefficient for Ep = 120, 160 MeV at θ = 0° was measured by (1990HUZY). Total cross sections for production of 19Ne measured by the activation method are reported by (1990WA10).
Many resonances occur in this reaction. They are displayed in 20.27 (in PDF or PS), 20.29 (in PDF or PS), and 20.28 (in PDF or PS) depending on whether they are observed in the α0 yield [20.23], in the α1 [or απ] yield to 16O*(6.05) [20.24] or in the α2, α3, and α4 yields [or in the yield of the γ-rays from 16O*(6.13, 6.92, 7.12) [20.25]]. See also Tables 2 and 3 in (1993DA23) which list a number of new resonances for Ep = 0.3 - 3.0 MeV. Resonances for α0 and α1 are required to have even J, even π or odd J, odd π, while the α2, α3, and α4 resonances are all odd-even or even-odd, with the exception of the T = 2 resonance.
Listings of the earlier yield studies are given in (1972AJ02, 1978AJ03, 1983AJ01). A detailed discussion of the evidence leading to many of the Jπ assignments is given in (1959AJ76). For values of θ2 see 20.28 (in PDF or PS) in (1978AJ03). Other measurements are reported by (1985OU01; 1.5 to 2.1 MeV; α0 → α3) and (1984IN04; 4.15 to 13 MeV; α0 → α5). In the latter work there are no marked correlations between the different channels.
Longitudinally and transversely polarized protons with Ep ≈ 0.67 MeV have been used to study 20Ne*(13.48) [Jπ = 1+; T = 1] via a parity- (and isospin-) forbidden α-transition. The state is not excited. The upper limits for the process, and their significance in the determination of fπ, the weak pion-nucleon coupling constant, are discussed by (1983KN01, 1986KN1C, 1990KN01). See also (1983AJ01, 1984KN1A).
Internal pair conversion for 19F(p, απ) of the 18 MeV GDR in 20Ne was studied by (1989MOZY) at Ep = 5.2 MeV.
A DWBA analysis for energies below the Coulomb barrier is used to determine the astrophysical S-factor in (1991HE16). See also (1993YA18).
Application-related work is reported in (1987EV01, 1989MC04, 1989MC03, 1989TA1N). See also the earlier work cited in (1987AJ02).
Levels of 20Ne derived from this reaction are displayed in 20.31 (in PDF or PS) in (1972AJ02) and 20.34 (in PDF or PS) in (1978AJ03). See also (1983LIZW).
Levels of 20Ne observed in this reaction are displayed in 20.35 (in PDF or PS) in (1978AJ03) and 20.32 (in PDF or PS) in (1983AJ01). Deuteron angular distributions have been studied at E(3He) = 9.5 to 21 MeV: see (1978AJ03). A more recent measurement of differential cross sections at E(3He) = 22.3 MeV and DWBA analysis was reported by (1994ARZY).
The excitation energy difference (ΔEx) between the 1+ and 1-, T = 1 states 20Ne*(11.26, 11.27) is 11.1 ± 0.7 keV (1983FI02). Γγ/Γα = 0.88 ± 0.05 for 20Ne*(12.22) [2+; T = 1] (1984CA08). Using (2J + 1)ΓαΓγ/Γ = 1.41 ± 0.23 eV (1980FI01), Γα = 0.32 ± 0.06 eV for 20Ne*(12.22) (1984CA08). The value of Γγ/Γ of 20Ne*(12.22) implies B(M1) = 0.07 W.u. for the transition from 20Ne*(18.43) [2+; T = 2]. This is much weaker than other isovector M1 transitions in 20Ne and a factor of five lower than predicted by shell model calculations: see (1984CA08).
In recent work at E(3He) = 25 MeV, differential cross sections were measured (1994VE04) for 20Ne levels at Ex = 0, 1.634 MeV. DWBA calculations were carried out and absolute values of C2S were extracted and compared with shell model calculations.
Angular distributions have been measured at Eα = 18.5 and 28.5 MeV: see (1978AJ03, 1983AJ01). The double differential cross section was measured at Eα = 30.3 MeV in a study of the reaction mechanism involving excitation of the 0+, 2+ and 4+ states at Ex = 0, 1.63, 4.25 MeV (1995IG03).
Angular distributions have been studied at E(7Li) = 34 MeV to a number of states of 20Ne. C2S values are consistent with those reported in the (d, n) and (3He, d) reactions: see (1978AJ03).
The decay is primarily to 20Ne*(1.63) with a half-life of 11.163 ± 0.008 s (1992WA04): see reaction 1 in 20F. Besides the principal decay to 20Ne*(1.63) [log f0t = 4.97], 20F also decays to 20Ne*(4.97) [Jπ = 2-] with a branching ratio of (0.0082 ± 0.0006)% (1987AL06) [log f0t = 7.20 ± 0.03; D.E.Alburger and E.K.Warburton, see (1987AJ02)]. The upper limit for the ground-state decay is 0.001% [log f0t > 10.5]. For other values and earlier references see 20.36 (in PDF or PS) in (1978AJ03). The energy of the γ-ray from 20Ne*(1.63) is 1633.602 ± 0.015 keV. Eγ for the 4.97 → 1.63 transition is 3332.54 ± 0.19 keV which gives Ex = 4966.51 ± 0.20 keV based on Ex = 1633.674 ± 0.015 keV for the first excited state. The shape of the β-spectrum is in good agreement with the predictions of CVC (1983AJ01, 1987AJ02, 1989HE11). β-γ angular correlations reported by (1988RO10) are close to the expectations based on CVC theory. For earlier work see (1978AJ03, 1983AJ01, 1987AJ02). The 20F(β-)20Ne decay is thought to play a part in heavy element nucleosynthesis (1988AP1A). See also (1989MA1U, 1989TA26).
The photoneutron cross section (bremsstrahlung photons) shows peaks at Ex = 17.78 ± 0.05, 19.00 ± 0.05, 20.15 ± 0.15 [main peak of the GDR], 22.6 ± 0.3, 24.9 ± 0.5 and 27.5 MeV [the latter three states are broad]: the integrated cross section to 28.5 MeV is 58 ± 6 MeV · mb [exhausting ≈ 20% of the dipole sum]. The cross section for (γ, tot) using monoenergetic photons shows a structure at 18 MeV and some fluctuations atop the broad giant dipole resonance, σmax ≈ 7 mb. The double photoneutron cross section, σ(γ, 2n), is dominated by a single peak at Eγ ≈ 20.5 MeV, σmax ≈ 1.1 mb. For references see (1978AJ03, 1983AJ01) and see the atlas of photoneutron cross sections with monoenergetic photons (1988DI02). The significance of reaction (c) to astrophysics is discussed by (1982SA1A, 1984FO1A).
The first 1+; T = 1 state in 20Ne is measured at Ex = 11262.3 ± 1.9 keV. The branchings to 20Ne*(0, 1.63) are (84 ± 5) and (16 ± 5)%, respectively (1983BE19). See also (1984BE26).
The 20Ne charge radius, < r2 >1/2 = 3.004 ± 0.025 fm. Form factors for many excited states of 20Ne with Ex < 8 MeV have been reported: see (1978AJ03).
At Ee = 39 and 56 MeV, the 180° inelastic scattering is dominated by the transition to a Jπ = 1+, T = 1 state at Ex = 11.22 ± 0.05 MeV with Γγ0 = 11.2+2.1-1.8 eV. A subsidiary peak is observed corresponding to a state 0.35 ± 0.03 MeV higher [if Jπ = 1+ or 2+, Γγ0 = 0.65 ± 0.18 or 0.40 ± 0.13 eV]. A number of small peaks are also reported corresponding to Ex ≈ 12.0, 12.9, 13.9, 15.8, 16.9, 18.0 and 19.0 MeV. Prominent electric dipole peaks are reported at Ex = 17.7, 19.1, 20.2, and 23 MeV, in addition to weaker structures between 12.5 and 15 MeV; and prominent electric quadrupole peaks are observed at Ex = 13.0, 13.7, 14.5, 15.0, 15.4 and 16.2 MeV and there is broad quadrupole excitation between 16 and 25 MeV. The GDR cross section integrated from 11 to 25 MeV contains about 65% of the dipole EWSR while over 90% of the isoscalar quadrupole EWSR is exhausted by the strength in the region 10 - 25 MeV.
For 11 < Ex < 24 MeV only two isovector M2 transitions appear: these are to 20Ne*(11.62, 12.10) with B(M2, k)(↑) = 64 ± 13 and 56 ± 13 μ2Nfm2 [orbital contributions are non-negligible]. The M1 transition to 20Ne*(11.26) is also observed but that to 20Ne*(13.48) is not: it is < 0.2 μ2N (1985RA08). For reaction (b) see (1978AJ03).
Reaction (c) has been studied in order to obtain the (γ, α0) cross section in the giant resonance region: the cross section at 90° for Ex = 15 to 24 MeV is dominated by an E1 resonance [1-; T = 1, with an admixture of T = 0 which permits the α0 decay] at Ex = 20 MeV; lesser E1 structures are reported at Ex = 16.7, 17.1, 21 and 22 MeV. A relatively strong 2+; T = 0 resonance appears at Ex = 18.5 MeV, and evidence is reported for increasing E2 strength below 16 MeV. For references to the early work see (1978AJ03, 1987AJ02). For more recent work see the reviews on nuclear dipole excitations (1987BE1G) and status of the shell model (1988BR1P). Other more recent theoretical work includes studies of large basis space effects in electron scattering form factors (1990AM01), correlated charge form factors and densities for s-d shell nuclei (1990MA63), electron scattering multipoles for symplectic shell model application (1992RO08), mass number dependence of the difference between electron- and muon-scattering charge radii (1989AN12), electron scattering from 20Ne in a microscopic boson model (1988KU07, 1988KU22, 1988KU17), and studies of (e, e'γ) reactions and electromagnetic currents in rotational nuclei (1990GA09). See also (1988BR1D, 1988ZH1F, 1990MO1J).
Inelastic pion scattering experiments at Tπ = 120 MeV and 180 MeV indicate a broad 2+ member of the Kπ = 0+4 band in 20Ne (1989BU14, 1995BU01). They report Ex = 9.00 ± 0.18 MeV, Γ = 0.8 MeV, B(E2(↑)) = 40.9 ± 2.0 e2fm4. Several other states in the first four Kπ = 0+ bands were studied by (1995BU01). See 20.30 (in PDF or PS).
For reaction (b), spectra have been measured and analyzed for initial pion momenta of 6.2 GeV/c (1991AM1B, 1992KI31).
An evaluation of neutron-induced reaction cross sections of 20Ne for En = 1 - 30 MeV is presented in (1991RE10). See also (1993DE32) and earlier work cited in (1978AJ03).
Angular distributions of elastically scattered protons and of a number of inelastic groups have been measured for Ep = 2.15 to 65 MeV [see (1978AJ03, 1983AJ01)] and at Ep = 0.8 GeV (1984BL14, 1988BL13; to 20Ne*(0, 1.63, 4.25, 8.7) (u); also Ay). The latter work confirms the large hexadecapole deformation of 20Ne. At Ep = 201 MeV, probable 1+ states at Ex = 11.25 ± 0.01, 13.51 ± 0.03 and 15.72 ± 0.05 MeV are reported by (1987WI03): There does not appear to be any quenching of the M1 strength. In addition 2- states are observed at 11.58 and 12.08 MeV with B(M2) = 64 ± 13 and 56 ± 13 μ2N as is a state of unknown Jπ at Ex ≈ 17 MeV (1987WI03). See also (1988CR1B), the measurements at Ep = 6.4 - 7.7 MeV (1992WI13), measurements at Ep = 60 - 180 MeV (1993PLZY), and the earlier work cited in (1978AJ03). For reaction (b) see (1984CA09, Ep = 101.5 MeV), (1992WI13, Ep = 6.4 - 7.7 MeV), and the earlier experimental and theoretical work cited in (1987AJ02). See also (1993MU28).
Theoretical work reported since the previous compilation includes relativistic DWBA calculations on inelastic scattering at Ep = 200 - 800 MeV (1988JO02), a large-basis-space microscopic-model analysis of 800-MeV inelastic scattering (1991AM1A), studies with a coalescence model of hypernuclear formation and mesonic atom production (1989WA14) in high energy collisions (1988WA16, 1989SA58), analysis of 800-MeV inelastic scattering with the Dirac formalism (1990PH01, 1990PH02, 1992DE31). See also the microscopic three-cluster study of 21-nucleon systems presented in (1993DE32).
Experimental data on multiplicity, correlations, and inclusive spectra of mesons and other particles produced in p + 20Ne reactions at Ep = 300 GeV are presented in (1992YU1A) and compared with model predictions.
For references to work on antiproton interactions see 20.16 (in PDF or PS) and "GENERAL section" here.
Angular distributions of deuterons have been reported at Ed = 10.0 to 52 MeV [see (1978AJ03, 1983AJ01)] and at Ed = 52 MeV (1987NU01). Differential cross sections for elastic and inelastic scattering of tritons (reaction (b)) were measured at Et = 33.4 MeV by (1992HA12) and analyzed by the coupled channels method. Potential parameters, deformation lengths and multipole moments were deduced. See also the calculations for these data described in (1992HA18) in which spin, parity and band assignments are discussed. The calculations suggest the assignments of Kπ = 2-, 2- and 0- respectively to the Jπ = 2-, 3-, 3- states at Ex = 4.97, 5.62 and 5.79 MeV. See also (1978AJ03, 1987AJ02).
Angular distributions have been measured at E(3He) = 10 to 35 MeV and at 68 MeV: see (1978AJ03). See references cited in (1978AJ03). More recently differential cross section for elastic and inelastic scattering of 3He were measured at E(3He) = 33.4 MeV by (1992HA12) and analyzed by the coupled channels method. Comparisons were made with triton scattering. Calculations for these data were described in (1992HA18) in which spin, parity and band assignments are discussed. Elastic scattering measurements at E(3He) = 30 and 45 MeV are described in (1992NAZQ).
Angular distributions have been measured at Eα = 3.8 - 155 MeV [see references cited in (1978AJ03)]. More recently measurements were made at Eα = 54.1 MeV (1987AB03), Eα = 50 MeV (1991FR02) and at Eα = 3.8 - 11 MeV (1991AB05). Inelastic cross sections were measured at Eα = 5.6 - 11.0 MeV (1992DA10), Eα = 50 MeV (1991FR02), and Eα = 50.5 MeV (1987BU27).
For reaction (b) see references cited in (1983AJ01, 1987AJ02) and the measurements at Eα = 155 MeV of cross sections and decay branching ratios for several excited states of 20Ne up to the giant quadrupole resonance by (1987SU09).
Theoretical studies related to these reactions include: α + 20Ne structures of 24Mg in a microscopic three-cluster (α + α + 16O) model (1987DE40), distributions of α-particle strengths in light nuclei (1988LE05), target clustering and exchange effects in internuclear interactions (1988LE06), stationary-state currents in nuclear reactions (1988MA30), a DWIA analysis of 20Ne(α, 2α)16O at Eα = 140 MeV (1988SH05), distortion effects in a microscopic 16O + 2α description of 24Mg (1989DE32), evidence for a parity dependence in the α + 20Ne interactions (1989MI12), an l-dependent representation of a Majorana potential (1990CO38), a strong-absorption model analysis of α scattering (1992RA21), a calculation of quasimolecular states in 20Ne(α, α) (1992GR15), optical model analysis of 20Ne(α, α) at Eα = 22.9 MeV (1993AOZZ).
Angular distributions have been studied at E(7Li) = 36, 68, and 89 MeV: see (1983AJ01).
For pion production see (1985FR13).
Elastic angular distributions have been measured at E(10B) = 65.9 and E(11B) = 115 MeV: see (1983AJ01).
Elastic angular distributions have been obtained at E(12C) = 22.2 to 77.4 MeV and at E(20Ne) = 65.9, 74 and 75.2 MeV [see (1978AJ03, 1983AJ01)] as well as at E(20Ne) = 72.6, 74.0 and 75.2 MeV (1982SH29). Elastic and inelastic scattering differential cross sections at E(20Ne) = 390 MeV were measured by (1993BO28).
For yield, fusion, total reaction cross section and fragmentation studies see the references cited in (1987AJ02). More recently fragmentation studies at E(20Ne) = 540 - 1096 MeV/nucleon were reported by (1990WE14) and at E(20Ne) = 400, 800 MeV/nucleon by (1988DU01). See also (1987AN20, 1994FU01). For pion production and for reaction (b) see references cited in (1987AJ02).
Theoretical studies carried out since the previous compilation include: resonances, heavy-ion radioactivity and new predictions for medium mass collective systems (1989CI1C), cascade model study of Λ particle productions in central collisions of light nuclei (1988IW02), comparison of quantized ATDHF and GCM theory applied to the 12C + 20Ne system (1990SL01).
Angular distributions have been studied at E(20Ne) = 50 and 94.8 MeV involving 16Og.s. and 20Ne*(0, 1.63, 4.25) [see (1983AJ01)], at E(16O) = 25.6 to 44.5 MeV (elastic; also to 20Ne*(1.63) at 31.3, 33.3 and 44.5 MeV)) and at E(20Ne) = 66.8, 115, 137 and 156 MeV (elastic) [see (1987AJ02) for references]. Yield and fusion cross section measurements have also been reported in several references cited in (1987AJ02). Excitation functions at θcm = 90° for Ecm = 21.5 - 31.2 MeV were measured by (1988HE06) and at θlab = 13° for Ecm = 22.8 to 38.6 MeV by (1989SA14). Measurements at projectile energies of 3.6 MeV/nucleon are reported in (1987AN20), and at 4.2 and 4.5 GeV/nucleon by (1988BO46, 1988BE2A).
Theoretical studies related to this reaction reported since the previous review include: calculation within the framework of the cascade model (1988IW02), molecular orbital theory for elastic and inelastic scattering (1989HE1I), derivation of the parity-independent interaction for 16O + 20Ne (1989GA1L), optical model analysis of resonant structure in 16O + 20Ne (1991GA14), and local representation of a deep parity- and L-dependent 16O + 20Ne potential (1993AI02).
Elastic angular distributions are reported at E(20Ne) = 68, 117, 140, and 156 MeV (1983SH25). For yield and fusion measurements see references cited in (1983AJ01, 1987AJ02). High-spin shape isomers for sd-shell nuclei were studied at Ecm near 1.6 times the Coulomb barrier for 20Ne + 20Ne by (1993BAZZ). Studies of the average number of interacting protons in 20Ne + 20Ne collisions of 36 GeV/nucleon were reported by (1987AN20).
Theoretical work related to the reaction includes: a study of mesonic atom production by a coalescence model (1989WA14), a formulation of the mesonic atom production probability with a coalescence model (1989SA58), hypernucleus production by heavy ions by a coalescence process (1989BA92, 1989WA14, 1989BA93).
Elastic angular distributions for reaction (a) have been measured at E(20Ne) = 50, 60, 80, 90, and 100 MeV [see (1983AJ01)] at 40 MeV (1983NA04; Sα for the system 20Ne + 24Mg = 0.08 ± 0.02) and at Elab = 55, 80 and 160 MeV/nucleon (1987BE38). For yield and fusion cross sections for reactions (a) and (b) see references cited in (1987AJ02). See also the review of high energy gamma production in heavy ion collisions (1989NI1D).
Elastic angular distributions are reported at E(20Ne) = 55.7, 63, 125, and 151 MeV (1983NG01). For yield, fusion and evaporation residue studies see references cited in (1987AJ02) and the study at E(20Ne) = 217, 194 and 384 MeV (1988GR12, 1989BA17, 1990BA18). A search for incomplete deep inelastic collisions at E(20Ne) = 216 MeV is reported by (1988ZH12). Neutral pion production was studied at E(20Ne) = 4 GeV by (1988JU02, 1989FO07, 1989FO1G). A description of those data by the cooperative model is discussed in (1989GH01). See also the calculation of total reaction cross sections presented in (1988JO02).
Angular distributions have been studied at E(20Ne) = 44.1 to 70.4 MeV and at 151 MeV: see (1983AJ01). For an evaporation residue study see (1982MO15). For yield and fusion measurements see (1983AJ01). The breakup of 20Ne at E(20Ne) = 92, 149 and 213 MeV involves 20Ne*(5.79, 6.73, 7.16, 8.78, 10.26, 11.95) (1986SH30).
See also the references cited in (1987AJ02) and see the Monte Carlo simulation method calculation for nuclear transfer (1988CH28), and the study of alpha clustering and shell effects related to this reaction (1989PU1C).
20Na has a half-life of 447.9 ± 2.3 ms: see reaction 1 in 20Na. It decays to a number of states of 20Ne, principally 20Ne*(1.63): see 20.31 (in PDF or PS). The ratio of the mirror decays 20Na(β+)20Ne*(1.63) and 20F(β-)20Ne*(1.63), (ft)+/(ft)- = 1.03 ± 0.02. β - γ correlation measurements, as in the decay of 20F, lead to an upper limit for the second-class contribution to the correlation which is consistent with zero: see (1983AJ01). A more recent measurement (1988RO10) concluded that the β - γ angular correlations in A = 20 are close to and may be in agreement with conserved vector current theory. β - ν - α triple correlation coefficient measurements for the transitions via the α-unstable 2+ states shown in 20.31 (in PDF or PS) lead to values of the isospin mixing amplitudes [and to a determination of the vector weak coupling constant] (1983CL01, 1989CL02). See also references cited in (1987AJ02) and the measurements of (1992KUZO, 1992KUZQ).
A general expression of the polarized spectral function for the (e, e'n) transitions is used by (1994CA27) to model this reaction.
The T = 1 states observed in this reaction, and the analog states observed in 20F in the (d, 3He) reaction, are displayed in 20.16 (in PDF or PS of (1978AJ03). T = 0 states are presented in 20.38 (in PDF or PS) of 1978AJ03).
Angular distributions have been reported at Ep = 26.9 to 43.7 MeV: see (1978AJ03, 1983AJ01). The angular distributions of the tritons to the ground state of 20Ne and to the first 0+, T = 2 state [Ex = 16.7329 ± 0.0027 MeV] have been fitted by L = 0 and the tritons to 20Ne*(18.4) by L = 2. The latter is the first 2+, T = 2 state. The 0+, T = 2 state [20Ne*(16.73)] decays by α0[(6 ± 5)%], α1 + α2[(35 ± 12)%], α3 + α4[(29 ± 12)%], p0+ p1+ p2[(14 ± 9)%] and p3+ p4+ p5[(13 ± 8)%] [measured branching ratios in percent are given in the brackets] to the final states in 16O and 19F. See (1978AJ03) for references and additional information.
Angular distributions have been measured at Ep = 10.0 and 45.5 MeV: see (1972AJ02). High resolution measurement at Ep = 1.08 - 4.15 MeV were carried out in a study of 94 resonances in 24Mg by (1987VA24) at Ep = 6.25 - 6.55 MeV. A study of 24Mg resonances excited by protons in the range Ep = 6.25 - 6.55 MeV is described in (1990MI24, 1991MI24). Detailed-balance tests of time reversal invariance are reported in (1994DR01, 1993MI19, 1993MI25). Parity nonconservation experiments are discussed in (1995MI28). See also (1987PA06, 1989KA06) which describe analyzing power measurements for this reaction. Measurements of the cross section at Ep ≤ 350 keV were carried out by (1989GO1N). Astrophysical implications are discussed. See also references to earlier work cited in (1987AJ02).
Cross sections for this reaction were calculated by (1987KA30) in a study of molecular structure of highly-excited states.
Production cross sections for 20Ne were measured at En = 5.20, 7.00, 16.20 and 19.05 MeV (1990LA09). Cross sections were calculated with preequilibrium emission and constant-temperature evaporation models by (1993KH09).
See (1984CA09). See also 1978AJ03).
Angular distributions have been studied to many states of 20Ne at Ed = 28 to 80 MeV [see (1978AJ03, 1983AJ01)] and at Ed = 54.2 MeV (1984UM04; to 20Ne*(0, 1.63, 4.25, 5.62)). 20.35 (in PDF or PS) in (1983AJ01) displays the observed states and Sα obtained from several analyses. For newer values of Sα see (1984UM04, 1986OE01). See also (1984PA18, 1986PAZJ). Measurements at several different incident energies were reported by (1988RA27, 1988RA20). Data were analyzed with finite-range DWBA calculations, and spectroscopic factors were obtained with different potentials. Comparisons with spectroscopic factors from 24Mg(3He, 7Be)20Ne were made.
Angular distributions have been studied at E(3He) = 25.5 and 70 MeV: see (1978AJ03). See also (1983AJ01) and (1986RA15). Measurements at E(3He) = 41 MeV were reported by (1988RA20, 1988RA27). Data were analyzed with finite-range DWBA calculations and spectroscopic factors were obtained with different potentials. Comparisons with spectroscopic factors from 24Mg(d, 6Li)20Ne were made.
The angular distribution for the ground state transition has been measured at E(12C) = 40 MeV (1982LI16) and at Ecm = 25.2 MeV (1990LE12). Coupled-channels calculations were used to study the back angle anomaly. The backward angle yield in the inverse reaction was studied at E(24Mg) = 90 - 126 MeV by (1990GL01). See also (1983AJ01, 1989OB1C).
Excitation functions were measured at θcm = 90°, Ecm = 25 - 34 MeV by (1989LE19). Data were compared with calculations involving the coupling to higher orders between elastic and α-transfer channels. Differential cross sections were measured at E(16O) = 71.4 MeV by (1995FUZW). The effect of the dynamic α-transfer polarization potential is discussed in (1989FI03).
This reaction was studied at Ecm = 31.57 MeV by (1989PO1J).