S. A. Kerr

A study of the low-lying states in 178Hf through the (n, γ) reaction☆

The nucleus 178Hf was studied through thermal neutron and averaged resonance neutron capture reactions. The γ-ray and conversion electrons were measured with high resolution spectrometers. A level scheme up to an excitation energy of ∼2.1 MeV was constructed. It includes ∼65 levels, most of which are ordered into 18 rotational bands. The level scheme is complete up to about 1800keV for spins between 2 and 5. The neutron binding energy was established to be at 7626.3 (3) keV. The consistent Q form of the IBA-1 (CQF) was used to describe the low-lying collective γ and Kπ = 0+ bands. The agreement with the data was found to be excellent for the energies and B(E2) ratios of the ground and γ bands, whereas the agreement was poor for the Kπ = 0+ bands.

Nuclear spectroscopic study of24Na

The nucleus24Na has been investigated by studying the gamma-rays emitted following thermal neutron capture in23Na, with curved crystal and Ge(Li) spectrometers. Of the 277 transitions assigned to24Na, 216 were placed in the24Na level scheme containing 45 levels, of which six (1,961, 1,977, 3,866, 5,810, 5,918, and 6,222 keV) are reported for the first time. An average gamma-ray multiplicity of 3.3 gammas per neutron capture was observed. The neutron binding energy was determined to be 6,959.73 (14) keV. The resulting level scheme is compared to shell and rotational model predictions.

Levels and gamma transitions of 40K studied by neutron capture

The 39K(n, gamma )40K reaction has been studied with thermal neutrons using curved-crystal, pair and Ge(Li) spectrometers. In total, 427 gamma rays have been observed and 302 were placed in a level scheme containing 62 levels below 5100 keV with energy errors mostly less than 100 eV. Nine levels were observed for the first time in the (n, gamma ) reaction. New information on spins and parities was deduced from the detailed gamma branchings. The neutron binding energy was determined to be 7799.55+or-0.08 keV. The level scheme is compared with shell and statistical-model predictions.

The level scheme of 134Cs

Abstract Low-lying states in 134 Cs have been investigated using the 133 Cs(n, γ) 134 Cs and 133 Cs(d, p) 134 Cs reactions with various spectroscopic techniques. Numerous excited states in 134 Cs have been established with energies up to 1267 keV. The experimental data on the lowest negative- and positive-parity states are in fair agrement with the calculations based on two quasiparticles coupled to a vibrator. For higher excited states the multiplets appear more mixed than predicted by the simple model.

The19F(n, γ)20F reaction

The gamma-ray spectrum emitted following thermal neutron capture in19F has been studied with curved crystal and Ge(Li) spectrometers. From the 109 transitions assigned to20F, 85 have been placed in a level scheme containing 26 levels. An average gammaray multiplicity of 2.8 gammas per neutron capture was observed. The neutron binding energy was found to be 6601.33(14) keV. The experimental level scheme is compared to rotational model predictions. In addition it is shown that the decay of the capture state is non-statistical and that there is a strong correlation between the strengths of excitation of levels by the (n, γ) and (d, p) reactions. Calculations of the partial cross-sections using the direct capture theory of Lane and Lynn give order of magnitude agreement with experiment.

Level structure of 42K from the 41(n, γ) and 41K(d, p) reactions ☆

Abstract The γ-ray spectrum emitted after thermal neutron capture in 41 K has been measured with pair and Ge(Li) spectrometers at the ILL high-flux reactor. About 630 transitions have been assigned to the decay of 133 excited states in 42 K. The level energies have been determined with a precison of 20 ppm; the neutron binding energy was determined to be E B = 7533.82(15) keV. On the basis of the many transitions to known states, several spin-parity assignments have been made. In addition, high-resolution proton spectra of the reaction 41 K(d,p) have been taken at 20MeV deuteron energy with the Munchen Q3D spectrometer. These data have been essential in establishing the newly-found levels and in differentiating between primary and secondary transitions in the (n, γ) work. A statistical analysis of the level density and relative strengths of primary transitions is given.

Neutron binding and excitation energies of some Pb isotopes

Improved neutron binding and excitation energies in205, 207, 208Pb, relative to the 412 keV gold standard, have been deduced from the measurements of gamma-ray energies following thermal neutron capture. Neutron binding energies of 6,731.57(15), 6,737.76(18), 7,367.87(11) keV for205, 207, 208Pb, respectively, were determined.

Low-lying positive parity states in 195Ir following double neutron capture

Abstract Multiple neutron capture reactions have been studied on 193 Ir targets and gamma and electron spectroscopy performed. Double neutron capture events were separated from all others and a level scheme of 195 Ir deduced. Gamma-ray energies and multipolarities are tabulated. A neutron capture cross-section for the reaction 194 Ir ( n , γ) of 1500±290 b has been determined and the neutron binding energy of 195 Ir measured to be 7231.92 (6) keV. The results are discussed in terms of perturbed spin(6) symmetry and U ( 6 4 ) supersymmetry. A σ σ max family of levels has clearly been identified.

An unusualM1 electromagnetic transition connecting octupole and quadrupole vibrations in179Hf

A detailed level scheme for179Hf has been constructed on the basis of extensive (n, γ), (d, p) and (d, t) data. The low lying levels are grouped into 15 rotational bands of which 14 are classified by Nilsson quantum numbers or vibrational configurations. One of the most interesting results concerns a dominant transition matrix element which connects an octupole vibration built on the 1/2[510] Nilsson orbit with a quadrupole vibration built on the 9/2+ [624] Nilsson ground state. A simple interpretation of this unusual decay mode is offered in terms of microscopic wave functions for the vibrational states. This interpretation leads to reasonable estimates forE1 hindrance factors from the octupole vibration to lower lying quasi-particle levels.

A study of the low‐lying states in 178Hf through the neutron capture reaction

The decay of the low‐lying states of 178Hf was investigated using: (1) High‐resolution curved crystal spectrometry of the secondary γ‐rays using the GAMS‐1 and GAMS 2/3 facilities at the ILL, (2) Measurements of the secondary (n,e−) transitions using the Electron Spectrometer BILL at the ILL, (3) Measurements of the primary γ‐transitions following thermal neutron capture with the pair‐spectrometer at the ILL and (4) Average Resonance Capture (ARC) measurements at the neutron energies of 2 keV and 24 keV, using the tailored beam facilities at BNL.