Energy levels in 93Mo populated by the 93Nb(p,nγ) reaction

Energy levels of ⁹³Mo have been investigated by means of the ⁹³Nb(p, nγ)⁹³Mo reaction. The excitation functions of the level de-excitation γ-rays were measured with a Ge(Li) detector under proton bombardment in the energy range 3.0 to 5.0 Me V. A detailed γ-ray decay scheme which includes 69 levels and 123 γ-ray lines was constructed from the threshold energies for 64 γ-rays and the γ-ray excitation functions around five isobaric analogue resonances in the ⁹³Nb(p, nγ) reaction. Spin-parity values for 59 levels and favourable values for 8 levels were assigned from the analysis of relative neutron yields via the isobaric analogue resonances of the parent odd-odd nucleus ⁹⁴Nb. The results of the present experiment are compared with shell-model calculations.     

Level Scheme of High-Spin States in 145Tb

High-spin states of ¹⁴³Tb have been studied via the ¹¹⁸Sn(³²S,1p4n)¹⁴⁵Tb reaction by means of in-beam γ-ray spectroscopy. Measurements of γ-ray excitation functions and γ-γ-t coincidences were performed with 12 BGO(AC)HPGe detectors. A level scheme for ¹⁴⁵Tb including 41 γ-rays which come from the deexcitations of the 24 levels, has been established for the first time based on an analysis of the γ-ray excitation functions, γ-γ coincidence relationships, intensity balances and cross-over transitions. The spins for most of the levels in the scheme are assigned according to the results of the measured γ-ray anisotropies. Considering the structure similarity between ¹⁴³Eu and ¹⁴⁵Tb, the low-lying levels in 145Tb are interpreted by coupling a h_9/2 proton to the excited states in ¹⁴⁴Gd core.     

Collective bands in even mass Sn isotopes

Positive parity bands in ^{112, 114, 116, 118}Sn have been excited up to levels with spin and parity J^π = 12⁺ using Cd(α, 2nγ)Sn reactions. The experiments consisted of γ-ray excitation function, γ-γ coincidence, lifetime, γ-ray angular distribution, γ-ray linear polarization and conversion electron measurements. The observed bands show strong resemblances with ground-state bands of transitional nuclei in this mass region. It is pointed out that the J^π = 0⁺ band-heads originate from 2p-2h excitations in the Z = 50 proton shell. The excitation energies of the band-heads are calculated by means of the macroscopic-microscopic renormalization method. Pair correlations between the 2h and 2p configurations are included separately in a phenomenological way by taking into account the pairing energies of the Cd and Te ground states with respect to the Sn ground state.     

An investigation of 73As energy levels by means of (p,n) and (p,nγ) reactions

The energy levels of ⁷³As were studied by means of the ⁷³Ge(p, n)⁷³As reaction at proton energies between 2.1 and 3.3 MeV. Neutron energies were measured by time of flight, and γ-ray energies with Ge(Li) detectors. The γ-decay of levels was studied by means of γ-n coincidences. Angular distributions were measured for the strongest de-excitation γ-rays, and relative excitation strengths of levels were derived from the neutron spectra. These are compared with predictions of the statistical theory to derive spins for a number of levels. A level and decay scheme for ⁷³As up to 1.98 MeV excitation is presented.     

Energy levels of 71Ge from 71Ga(p,nγ)71Ge

Energy levels of ⁷¹Ge were populated by the ⁷¹Ga(p, n) reaction at proton energies between 1.72 and 2.96 MeV and their decay studied by both γ-γ and γ-n coincidences. Spins were determined within the framework of the statistical theory from angular distributions of de-excitation γ-rays and from excitation strengths of levels derived from γ-ray intensities and branching. A level and decay scheme for ⁷¹Ge up to an excitation of 1.3 MeV is presented.     

Non-yrast states and shape co-existence in light Pt isotopes

Low-lying states in the even-even light platinum isotopes ¹⁷⁶Pt, ¹⁷⁸Pt, ¹⁸⁰Pt and ¹⁸²Pt have been populated using β⁺ /EC decay from parent gold nuclei, created in (HI,xn) reactions. State energies, spins and parities and γ-ray branching ratios were determined using γ-ray and electron spectroscopy. Whereas non-yrast states were observed in ¹⁷⁸Pt, ¹⁸⁰Pt and ¹⁸²Pt, none were seen in ¹⁷⁶Pt. The excitation energies of the observed states are analysed in terms of a band-mixing model, yielding the moments of inertia of the unperturbed bands. Branching ratios and ground-state-band quadrupole moments are calculated and compared with experimental values. The results indicate that the two lowest-lying 0⁺ states in each of the light Pt isotopes are formed from the mixing of two intrinsic states of different deformation, and other low-lying states can be described as admixtures of rotational states built on these intrinsic states, and on γ-vibrational states.     

A new experimental method for the study of regions of high spin and excitation energy

The excitation energy in ⁷²Se populated in the reaction ⁵⁸Ni(¹⁶O, 2pγ) for energies between 54.5 and 64.5 MeV has been measured by summing the γ-energy released in each γ-ray cascade. The average γ-multiplicity is simultaneously measured as a function of summed γ-energy. The method is useful for studying the highest regions of angular momentum and excitation energy.     

Gamma-ray multiplicities in α-induced compound and precompound reactions

Measurements of γ-ray multiplicities from the¹⁵⁰Sm(α, xn) reactions at beam energies from 40–140 MeV show that the maximum angular momentum transfer occurs at an energy between 12 and 18 MeV higher than that of the maximum of the excitation function for the respective exit channel. At still higher bombarding energies, where precompound processes dominate, a decrease of the multiplicity is observed.     

Energy levels of 24Na from the 23Na(d,pγ)24Na reaction

Excited states in ²⁴Na have been investigated by means of the ²³Na(d, pγ)²⁴Na reaction at incident deuteron energies of 2.5 and 2.8 MeV. Excitation energies and γ-ray decay for levels up to 4.2 MeV have been determined from proton-gamma coincidence spectra obtained with a surface barrier detector and a Ge(Li) detector on-line with a computer. Two new levels at 3944 ± 2 and 4195 ± 3 keV excitation energies are reported.     

Level structure of the doubly odd nucleus 112In from the (p,nγ) reaction

Properties of the levels in ¹¹²In have been studied with the reaction ¹¹²Cd(p, nγ)¹¹²In. The level scheme of ¹¹²In below 1300 keV was constructed from the γ-ray excitation functions and γγ coincidences. In ¹¹²In, 22 excited states were observed and spins and parities of 8 excited states were newly assigned or restricted by comparing the measured angular distributions and linear polarizations of the deexciting γ-rays as well as the excitation functions of the residual levels with the predictions of the statistical compound nucleus model. Possible configurations of the low-lying levels are discussed in terms of their decay properties and the systematics of the excited states in the neighbouring doubly odd In isotopes.     

The (p,nγ) reaction on Al and Si

The reactions ²⁷Al(p, n γ) ²⁷Si and ²⁸Si(p, n γ)²⁸P have been studied at E_p = 16 and 23 MeV, respectively, with a Ge(Li) detector in coincidence with a neutron detector. In ²⁷Si, two new γ-tran- sitions were detected and accurate excitation energies were determined. In ²⁸P, the γ-decay scheme was studied for the first time and new levels were located at 879 and 1602 keV excitation energy. For both nuclei the γ-ray spectra were supplemented by neutron time-of-flight spectra. The excitation energies are compared with those of the analogue nuclei and with the predictions from Coulomb displacement calculations.     

Luminescence and ESR characteristics of γ-irradiated Lu3Al5O12:Ce single crystalline film scintillators

The influence of γ-irradiation with a dose of ～10⁴ Gy on the characteristics of LuAG:Ce single crystalline films (SCF) was investigated using ESR and time-resolved luminescence spectroscopy under excitation by synchrotron radiation with the energies ranging from 3.7 to 12 eV. The origin of γ-ray induced radiation defects in LuAG:Ce SCF is discussed.     

Evidence for deformed states in 75Br

The excited states in ⁷⁵Br have been studied via the reactions ⁷⁴Se(p, γ), ⁷⁴Se(d, n), ⁷⁴Se(³He, pn) and ⁷⁴Se(α, p2n) by using in-beam γ-ray spectroscopy. In addition to measurements of γ-γ coincidences, excitation functions and angular distributions of γ-rays, ns lifetime measurements have also been carried out. As a result 19 levels have been identified up to spin ($\text{17}\text{2}$) and excitation energies up to 2.6 MeV. The B(E2) value of 88 W.u. derived for the 88.4 keV γ-ray indicates strong collectivity within a positive-parity band. A comparison of the excitation energies of the unique-parity states in ⁷⁵Br and ⁷⁷Br with those in ¹⁵³Tb and ¹⁵⁵Tb reveals that the average deformation increases when going from ⁷⁷Br (N = 42) to ⁷⁵Br (N = 40).     

The excitation functions and Isomer ratios for neutron-induced reactions on Mo and Zr

Absolute cross sections of the reactions ⁹²Mo(n, 2n)^91m,91gMo, ⁹²Mo(n, p)⁹²Nb and ⁹²Mo(n, α)^{89m, 89g}Zr, relative cross sections of the reaction ⁹⁰Zr(n, 2n) ^89mZr and isomer ratios of the ⁹⁰Zr(n, 2n) reaction have been measured in the neutron energy range 13–15 MeV. The results for the (n, 2n) reactions are in good agreement with those of the previous studies. The present results for the (n, p) and (n, α) reactions are in disagreement with the previous works. The experimental data are analysed by the statistical model to determine the level-density parameter a, the moment of inertia ? and the strength of the γ-ray transition S_l in order to simultaneously reproduce the experimental data on the excitation function and the isomer ratio in the (n, 2n) reaction. The γ-ray competition, the yrast level and the experimental information on the excited levels of the residual nucleus in the (n, 2n) reaction are taken into account. The obtained values of a, ? and S_l are consistent with those deduced from other types of nuclear data.     

Isomer ratio measurements for the reaction 29Si(18O,p2n)44m, 44gSc

Isomer ratios for the reaction ²⁹Si(¹⁸O, p2n)^44gSc, ^44gSc have been deduced from activity measurements for projectile energies between 30 and 99 MeV. Statistical model calculations show that the isomer ratio dependence on projectile energy up to about 80 MeV can be adequately described by assuming a fixed ratio of quadrupole to dipole γ-ray strengths. Such a ratio of E2/E1 strengths agrees with corresponding values deduced from the literature. The values of the γ-ray strength ratios needed to fit the experimental isomer ratios are extremely sensitive to the relative amounts of quadrupole γ-ray admixture and to the presence of discrete levels other than those which conform to the yrast line.     

The 69ga γ-ray strength function between 6–10 MeV

The (p, γ) reaction on ⁶⁸Zn has been studied for proton energies between 2.18–2.69 and 3.13–3.56 MeV. Hauser-Feshbach calculations for the two proton energy ranges have been performed. From these calculations the ⁶⁹Ga γ-ray strength function between 6–10 MeV has been deduced.     

Decay of the compound nucleus 74Kr formed in the reaction 16O + 58Ni

Gamma-ray and charged-particle emission has been studied after bombardment of ⁵⁸Ni with ¹⁶O at energies from 44.5–76.5 MeV. The excitation functions for various reaction channels have been measured. The locus in energy and spin of maximum cross section (the entry line) of the γ-emitting region in the 2pγ and 3pγ channels have been studied through measurement of γ-ray multiplicity, average particle energy and average γ-ray energy. The standard deviations in both energy and spin of the distributions of cross section are presented. Statistical model calculations including shell corrections in the level density show very satisfactory agreement with the experimental results. The moment of inertia at high spin and excitation energy is deduced from the measured entry line.     

Etude du noyau 63Cu par la reaction 60Ni(α, pγ)63Cu

The level structure and the decay properties of low-lying levels in ⁶³Cu have been investigated via the ⁶⁰Ni(α, pγ)⁶³Cu reaction at E_α = 11.7MeV. Using a Ge(Li) detector, the correlations of twenty-five primary γ-rays in coincidence with protons, stopped in an annular detector at approximatively 180° with respect to the beam direction, were measured. From these measurements, branching ratios, γ-ray mixing ratios and spin assignments have been obtained for most of the levels up to 2.4 MeV excitation.     

Band crossings in 128Ba

Excited states of ¹²⁸Ba have been studied by in beam γ-ray and conversion electron spectroscopy using the ¹¹⁸Sn(¹³C, 3n)¹²⁸Ba reaction. 28 new levels were found, 16 spin and parity assignments were made and 4 new bands were identified. The low-lying two-quasiparticle bands were compared with cranked shell model calculations. The low-lying collective levels are discussed in the framework of the interacting boson model.     

The level structures of the nuclei232Th and238U

Time-of-flight gating techniques have been used to study the decay γ-rays from states excited by inelastic scattering of neutrons from²³²Th and²³⁸U. Neutron energies up to 1900 MeV have been used. From accurate determinations of the γ-ray energies, intensities and thresholds, detailed level and decay schemes have been obtained for²³²Th and²³⁸U. New levels in both nuclei are observed at larger excitations than before and the present work is incompatible with some previously accepted spin and collective band assignments derived from Coulomb excitation studies.