States Of 21Na Research Articles

Exotic structure of the third excited state in21Na

The probability of the last proton being out of the binding potential,P and the root-mean-square (rms) radius («r2»1/2= of the third excited state in21Na are calculated by means of asymptotic normalization coefficient (ANC) method with the experimental date existing. The results are P=54.73% and «r2»1/2=5.28 fm respectively. TheP value and the contribution of the asymptotic part to the «r2»1/2 are compared with those of several other low energy states in21Na. It is found that the valence particle in the third excited state has an obvious largerP than those of other states. The density distribution of the valence proton in this state is also compared with the nucleons in the nuclear core20Ne, and a far extended tail can be seen clearly. These results show that the third excited state in21Na is a proton halo state.

Exotic structure of the third excited state in 21Na

Exotic structure of the third excited state in 21Na

Halo Structure of Isobaric Analogue States in A = 21 and 17 Mirror Nuclei

The root-mean-square (rms) radii of the last nucleons in the2s1/2 states of 21Ne, 21Na, 17O and 17F arefound to be 4.4±0.5, 5.2±0.6, 4.3±0.5 and5.0±0.6 fm, respectively, from transfer reaction data. Theresults show that the 2s1/2 states of 21Na and 17F areproton halo states, while the analogous states in their mirror nuclei21Ne and 17O can be considered as neutron skin states.Comparisons among the rms radii of these states lead us to expectthat a neutron halo nucleus has a proton halo mirror partner, and theCoulomb barrier is a determinant factor limiting the extension of therms radius of the loosely bound proton.

Magnetic moment of the first excited state in21Na

Magnetic moment of the first excited state in21Na

Isospin-forbidden [formula omitted] resonances in 25Al, 29P and 33Cl, and the systematics of isospin mixing

The two lower T = 3 2 states in 25Al and the lowest T = 3 2 states in 29P and 33Cl were observed as isospin-forbidden proton elastic-scattering resonances. The widths of these states were deduced by combining polarisation analysing-power data in the vicinity of these resonances with high-resolution cross-section data in an analysis incorporating the effects of finite beam resolution (≈ 650 eV), Doppler broadening, and straggling of the incident beam in the target. A new estimate of Γ for the lowest T = 3 2 state in 21Na was obtained by re-analysing previously measured data. The elastic-proton reduced widths γ p 2 of the T = 3 2 states observed in scattering from T = 0 nuclei with 8 ≦ A ≦ 40 are well represented by the formula γ p 2 = cA 2.4 where c = 0.128 ± 0.007 eV for target nuclei with A = 8 n + 4 and c = 0.023 ± 0.009 eV for A = 8 n, where n is integral. Possible mechanisms for this behavior of γ p 2 which is not predicted by previous calculations, are discussed.

On21Na states betweenE x=5.5 and 6.2 MeV

States in21Na between 5.5 and 6.2 MeV have been investigated by means of the20Ne(p, p)20Ne,20Ne(p, p′20Ne and20Ne(p,p′γ)20Ne reactions. The gas target is Ne in naturally occurring abundances or enriched to 99.9 % in20Ne. No new levels were seen but a new value of the spin of the 5.814 MeV state is given: (ie353-01)= 7/2−. The (ie353-02)=(5/2, 7/2)− assignment of the 6.076 MeV level is confirmed.

DSA lifetimes in21Na and23Na derived from experimental stopping parameters

The lifetimes for the second excited state in21Na and for the second to ninth excited states in23Na have been determined with the DSA method using Ta2O5 and Ta as stopping materials. In the DSA analysis the experimental stopping parameters determined in the present and earlier works were utilized. The reanalysis of some earlier studies has brought very good consistency to the scattered results. Comparison of the observed transition strengths with theory has also been made.

The 2425 keV state in 21Na as a subtreshold resonance in 20Ne (p,γ)21 Na

The high-energy tail of the Jπ = 12+, 2425 keV state in 21Na, bound by 7 keV against proton decay, has been observed in the 20Ne (p,γ)21Na reaction at Ep=0.5−1.5 MeV. The observed excitation function is consistent with a single-level Breit-Wigner shape with Γγ=0.31±0.07 eV at Ex = 2425 keV.

The lowest negative parity state in 21Na

The 20Ne(d, n) 21Na reaction has been studied at E d = 4.5 MeV. The neutron angular distributions indicate l p = 0 and 1 for the 2.41 and 2.79 MeV levels, respectively. The 2.79 MeV level is interpreted as the head of a rotational band based on Nilsson orbit 1 2 − [101].

Structure of 21Na from the 24Mg(p, α) 21Na reaction

The lower excited states of 21Na were studied using the 24Mg(p, α) 21Na reaction at a bombarding energy of E p = 17.5 MeV. From analysis of particle-ray-γ angular correlations the spins of the 332, 1723 and 2834 keV states were found to be J = 5 2 or ( 3 2 ), 7 2 or ( 3 2 ) and 9 2 or ( 5 2 ) , respectively. Branching and multipole mixing ratios were obtained as well as evidence for a doublet of states with excitation energies 2833.8 ± 4.0 and 2803.5 ± 5.0 keV. This removes a puzzle of long standing concerning an apparent missing state in 21Na as compared to the mirror nucleus 21Ne. The experimental information obtained in the present study is compared with that for the mirror nucleus, 21Ne, and discussed in terms of a Coriolis coupling model. These data, and those to be reported in subsequent papers for adjacent nuclei, suggest strongly that these nuclei may well be among the most rigid in nature.

T = [formula omitted] states in 21Na as seen in the 20Ne(p, p) 20Ne reaction

The two lowest T = 3 2 states in 21Na have been observed as narrow scattering anomalies in 20Ne(p, p) 20Ne, using a differentially-pumped gas target. The observed resonance energies are E p = 6.872 ± 0.005 MeV and E p = 7.128 ± 0.005 MeV corresponding to E x = 8.973 ± 0.007 MeV and E x = 9.217 ± 0.007 MeV in 21Na. No other narrow scattering anomaly was found in the proton laboratory energy range 6.76–7.33 MeV although six anomalies of width greater than 13 keV were seen. From an analysis of the data using single level dispersion theory the following parameters were extracted for the T = 3 2 states: for the 8.973 MeV state, J π = 5 2 + (or 3 2 +) , ⊥ total < 1.2 keV , ⊥ po = 0.10 ± 0.05 keV and, for the 9.217 MeV state, j π = if 1 2 + , ⊥ total = 2.3 ± 0. 5keV and ⊥ Po = 1.1 ± 0.3 keV.

Optical pumping of short lived Β-radioactive isotopes and the magnetic moment of37K

21Na (T1/2=23 sec) and37K(T1/2=1.25 sec) have been produced in gas targets by (d, n) reactions and polarized by means of optical pumping or spin exchange scattering with optically pumped87Rb. An asymmetry up to 3% in theΒ-decay of the polarized nuclei was found, which served to detect rf transitions between hfs levels of the atomic ground states of21Na and37K.δF=0 andδF=1 resonances have been recorded, yielding spin, hfs separation and magnetic moment, especiallyI(37K)=3/2,δW(37K)=240.266 (3) Mc/sec andΜI(37K)=0.02033(6) nm (diamagnetically corrected). For21Na earlier rf-spectroscopic data have been confirmed.

Several narrow resonances in the proton bombardment of 20Ne

States in 21Na at 3.544, 3.680, 3.864 and 4.293 MeV have been studied by proton elastic scattering and radiative capture in 20Ne. The properties of these states are compared with the corresponding states in 21Ne and with the predictions of the Nilsson model.

DELAYED PROTONS FOLLOWING 21Mg AND 25Si DECAY

The delayed-proton precursors 21Mg and 25Si have been produced by proton bombardment of targets of sodium, magnesium, aluminum, and silicon dioxide in the internal beam of the McGill synchrocyclotron. Half-lives of 118 ± 4 and 225 ± 6 msec respectively were measured, and a spin-parity assignment of (5/2)+ has been made to the ground state of 21Mg. Strong lines in the delayed-proton spectra have been attributed to decay of the expected first T = 3/2 states in 21Na and 25Al, fed by superallowed β transitions from the respective precursors 21Mg and 25Si.