J.L. Durell

Lifetimes and decays of energy levels in 30Si and 30P

Abstract The mean lifetimes of 15 levels in 30 Si and of 7 levels in 30 P have been measured by the Doppler-shift attenuation method. Limits on the lifetimes of a further 8 levels in 30 Si and of the 3018 keV level in 30 P have been obtained. Branching ratios and excitation energies have been measured in both nuclei. The levels were populated by the reactions 27 Al(α, p) 30 Si and 27 Al(α, n) 30 P at α-particle bombarding energies of 5.0, 6.3 and 8.0 MeV. Theγ-rays were detected with a Ge(Li)-NaI(Tl) escape suppressed and pair escape spectrometer.

Neutron orbit sizes in the isotopes of tin

Root-mean-square radii of 3s12, 2d32, 1g72 and 1h112 neutron orbits in the isotopes of tin with A = 113, 115, 117, 118, 119 and 120 have been determined from a DWBA analysis of cross section data from the sub-Coulomb (t, d) reaction. The differential cross sections for the (t, d) reaction were measured at lab angles in the range from 120° to 160° for triton energies in the range from 4.25 MeV to 5.75 MeV. Spectroscopic factors of the populated states were obtained from a sum rule analysis of published neutron stripping and pickup reactions on the isotopes of tin. The measured rms orbit radii were used in a calculation of the rms radii of the neutron excess in the even tin isotopes, and the resulting values were compared with those extracted from an analysis of Coulomb displacement energies. The behaviour of neutron orbit size and parameters of the neutron bound state potential within the isotopic sequence of final nuclei is discussed. The systematics of matter, charge and neutron radii are discussed.

Proton orbit sizes and the electric monopole matrix element in 90Zr

Abstract The mean square radii of the 1 g 9 2 , 2 p 1 2 and 2 p 3 2 proton orbits in 90Zr have b een measured and used in an evaluation of the E0 matrix element between the two lowest 0+ states in 90Zr. The E0 proton effective charge is deduced to be 1.37±0.23.

Lifetimes and decay modes of energy levels in 34S

Abstract The excitation energies, branching ratios, and mean lifetimes of the low-lying levels in 34 S were measured. The lifetimes were measured by the Doppler shift attenuation method using the 31 P(α, p) 34 S reaction at a bombarding energy of 7.0 MeV. The γ-rays were detected at six angles with a Ge(Li)-NaI(Tl) anti-Compton and pair spectrometer. The mean lifetimes, in fs, were found to be: 2127 keV, 440 ± 50; 3303 keV, 218±30; 3915 keV, 1600±130; 4075 keV,

The mass of 33Al

Abstract The reaction 48 Ca(S, 33 Al) 51 V at E =198 MeV has been used to measure the mass excess of 33 Al; a value of −8.53±0.14 MeV was obtained. This result is compared with the results of recent large-basis shell model calculations and the discussion is centered around the significance of the present measurement within the context of the proposed region of nuclear deformation around Z =11, N =20.

Lifetime measurements in 40K

The Doppler-shift attenuation method has been used to measure the lifetimes of 19 levels in 40K and four levels in 40Ar. Limits have also been set on the lifetimes of other levels in 40K. The measurements were made using the 37Cl(α, n)40K and 37Cl(α, p)40Ar reactions. Enriched targets of lead chloride and barium chloride were used. The lifetimes obtained with different stopping materials and different recoil velocities were compared where possible and were found to be consistent. A γγ coincidence experiment was performed to elucidate the decay schemes in 40K and 40Ar. The negative-parity states of 40K have γ-ray decay schemes consistent with simple shell-model calculations for d32−1f72 and d32−1p32 configurations. More information is needed before the 2p-2h and 4p-4h positive-parity states can be classified.

Lifetimes of levels in 23Na below 5 MeV

Abstract The lifetimes of seven states in 23Na have been measured with the attenuated Doppler shift method. Transition strengths are compared to theoretical predictions where the levels are assumed to be members of either K= 3 2 + , 1 2 + or 1 2 − rotational bands.

The 1h92 proton orbit size in 209Bi

Abstract Angular distributions of α-particles from the reaction 209Bi(t, α)208Pb (ground state) have been measured at bombarding energies Et = 8.5 MeV and Et = 9.0 MeV. Zero-range (ZR) DWBA analyses of the data are used to determine the radial extent of the wave function of the lh 9 2 orbit in which the transferred proton is bound in 209Bi. The applicability of the sub-Coulomb ZR DWBA treatment is investigated by comparison of ZR and exact finite-range DWBA calculations. A value of the (t, α) normalization constant of (20.8 ± 3.1) × 104 MeV2 · fm3, based on forward dispersion relations, has been obtained from this comparison. The asymptotic amplitude of the wave function is measured directly and the rms radius is extracted via a Woods-Saxon model. A value of √〈r2〉 = 6.10−0.08+0.12 fm, corresponding to a point proton and to a local Woods-Saxon potential, is obtained. The rms radius and radial wave function of the 1 h 9 2 proton are compared with the results of electron scattering and muonic atom data on targets of 209Bi and 208Pb and with the results of Hartree-Fock calculations.

Radii of single-proton states in isotopes of tin

Abstract Sub-Coulomb (t, α ) reactions have been employed in the determination of the rms radii of the 1 g 9 2 , 2 p 1 2 and 2 p 3 2 proton orbits in 112,116,118,120,124 Sn. The experimental values are compared to the results of Hartree-Fock calculations.

THE mass of 37P

Abstract The mass excess of 37 P has been measured using the 48 Ca( 36 S, 37 P) 47 Sc reaction at E = 198 MeV. A value of −19.06 ± 12 MeV was obtained. This value is compared with two recent measurements and with the predictions of mass formulae.