B. Krusche

Gamma ray energies and 36Cl level scheme from the reaction 35Cl(n, γ)

Abstract The γ-ray spectrum emitted after thermal neutron capture in 35Cl has been studied by use of the crystal and pair spectrometers installed at the ILL high flux reactor. We identified about 400 transitions in this reaction 326 of which were placed into the 36C1 level scheme; several new states were found. The level energies up to 3.5 MeV were measured with a precision of 5–20 eV relative to the 412 keV 198Au standard, those above 3.5 MeV with a precision of 10ppm. The neutron binding energy was determined to be EB = 8579.68(9) keV.

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.

Level structure of 87Sr from the 86Sr(n, γ) and 86Sr(d, p) reactions

Abstract The γ-ray spectrum emitted after thermal neutron capture in 86 Sr was studied at the ILL high flux reactor with pair- and intrinsic Ge spectrometers. 759 transitions were assigned to the reaction 86 Sr(n, γ) 87 Sr and 385 of them were placed into a 87 Sr level scheme of 80 levels. This represents 90% of the observed intensity. The level energies were determined with a precision of better than 20 ppm; the neutron binding energy was determined to be 8428.16 (17)keV. In a second set of experiments high resolution particle spectra of the reactions 86 Sr(d, p) 87 Sr and 88 Sr(d, t) 87 Si were recorded at 20 MeV deuteron energy with the Munchen Q3D spectrometer. These data were used to establish newly found levels and to differentiate between primary and secondary transitions in the (n, γ) data. The observed level densities and primary transition strengths are compared with statistical models.

High-resolution spectroscopy of 32P: (II). Level density and primary transition strengths observed after thermal neutron capture in 31P☆

Abstract The -γ-ray spectrum emitted after thermal neutron capture in 31P was studied at the ILL high flux reactor with a pair spectrometer and an intrinsic Ge detector. A total of 212 transitions were assigned to the decay of 32P and 155 of these, representing 96.7% of the observed flux, were placed in a level scheme of 38 states. The neutron binding energy was determined as 7935.74 (16) keV. The densities of states observed in this reaction and in a recent (d, p) study are analyzed in the constant temperature Fermi-gas model. The primary E1 and M1 transition strengths in 32P are discussed and are compared to other sd-shell nuclei.

Spectroscopy of 41K by thermal neutron capture in 40K

Abstract The γ-ray spectrum emitted after thermal neutron capture in 40K has been studied at the ILL high flux reactor with curved crystal Bragg, pair and Ge(Li) spectometers. 585 transitions were assigned to the reaction 40K(n, γ)41K and 490 of them were placed into a 41K level scheme; 68 new states are proposed. On the basis of γ-ray branches to states with established spin and parity, many new spin-parity assignments were made. The level energies up to 4 MeV were measured with a precision of 8–50 eV relative to the 411.8 keV 198Au standard, those above 4 MeV with a precision of 50–100 eV. The spin of the capture state was found to be I = 7 2 ; the neutron binding energy was determined to EB = 10095.25(10) keV. The level density of I π = 5 2 ± , 7 2 ± , 9 2 ± states was analyzed in terms of the constant-temperature Fermi gas model. It was shown that in this spin window the level scheme is almost complete up to an excitation energy of 5 MeV.

Nuclear structure of 156Gd studied with (n, γ), (n, e−), (d, p), (d, t) reactions and lifetime measurements

Abstract The nucleus 156 Gd was studied with (n, γ) and (n, e − ) reactions at the Institut Laue-Langevin (ILL) in Grenoble. The (d, t) and (d, p) reactions were investigated at the Munich Tandem Accelerator. Primary gamma rays following average resonance capture were observed at the Institut for Nuclear Research in Kiev. Summed coincidences measurements were carried out at the Reactor IBR-30 in Dubna. An extensive level scheme was constructed up to 2.35 MeV including 413 transitions and 18 band assignments. Lifetimes of 16 selected levels were measured with the Gamma-Ray Induced Doppler broadening method at the ILL. Low-lying bands of positive and negative parity were interpreted in the framework of the spdf-IBA. The agreement was found to be quite good.

Spectroscopy of 88Sr with the 87Sr(n, γ) and 87Sr(d, p) reactions☆

Abstract The γ-ray spectrum emitted after thermal neutron capture in 87 Sr was studied at the ILL high flux reactor with pair- and intrinsic Ge-spectrometers. 661 transitions were assigned to the reaction 87 Sr(n, γ) 88 Sr and 205 of them were placed into a 88 Sr level scheme of 47 levels. This represents 88% of the observed intensity. The level energies were determined with a precision of better than 20 ppm; the neutron binding energy was determined as 11 112.69 (22) keV. To aid the analysis high resolution particle spectra of the reaction 87 Sr(d, p) 88 Sr were measured at 20 MeV deuteron energy with the Munich Q3D spectrometer. 85 states were observed with this reaction. The data helped to establish newly found levels and to differentiate between primary and secondary transitions in the (n, γ) data. The observed level densities and primary transition strengths are compared with statistical model predictions and non-statistical effects are discussed.

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.

Level structure of 89Sr investigated with thermal and fast neutron capture and the (d, p) reaction☆

Abstract The γ-ray spectrum emitted after thermal neutron capture in 88Sr was studied at the ILL high flux reactor with a pair-spectrometer and an intrinsic Ge detector. A total of 221 transitions were assigned to the decay 89Sr, and 55 of these, representing 55% of the observed flux, were placed in a level scheme of 19 states. The neutron binding energy was determined as 6358.73 (13) keV. Neutron capture in the 23.6 keV 3 2 − resonance was studied at the BNL filtered beam facility. Only seven transitions were attributed to 89Sr, and the decay of the capture state was found to be dominated by the valence process. High resolution (d, p) spectra were recorded at 20 MeV beam energy at the Munich Q3D spectrometer, and 55 states up to 4.5 MeV excitation energy in 89Sr were populated. The density of states observed in (n, γ) and (d, p) is analyzed in the Fermi-gas model, and the distribution of single-particle strengths is discussed from a statistical point of view.

GRID lifetime measurements in59, 61, 63Ni following thermal neutron capture

The GRID-method has been used to measure the lifetimes of ten excited states in59, 61, 63Ni following thermal neutron capture in Ni targets of natural isotopic composition. Four of the lifetimes have been determined for the first time, the other six lifetimes can be compared with the results of conventional DSA-measurements following charged particle induced reactions. Cascade feeding effects have been included in the analysis. Level energies and electromagnetic properties of negative parity states in59Ni have been compared with the results of shell model calculations in 3p0h and 4p 1h model spaces. Statistical model estimates of the lifetimes as function of excitation energy and spin are also given.