Studies of single-neutron holes in the transitional nuclei N = 83–89: The 142Ce(d,t)141Ce and 142Ce(3He, α)141Ce pick-up reactions

The level structure of ¹⁴¹Ce up to 3.7 MeV excitation energy has been investigated by the (d, t) and (³He, α) reactions using 17 MeV deuteron and 24 MeV ³He beams respectively. The angular distributions have been analyzed with standard DWBA calculations and spectroscopic factors are deduced. The experimental information is compared to unified model calculations involving both one-particle and two-particle one-hole configurations with quadrupole and octupole vibrations of the underlying N = 82 and N = 84 core.     

Comparative analysis of (p,d), (d,t) and (3He, α) reactions on13C nucleus

The angular distributions of the (p, d), (d, t) and(³He, ) reactions on¹³C have been analysed within the framework of DWBA in which additional information on nuclear vertex constants was introduced. Although all these reactions seem to be similar single nucleon transfer, their mechanism is shown to be quite different and so is the information extracted thereof. While from the (p, d) reactions spectroscopic factors may be extracted unambiguously, from the (d, t) reactions it is possible to obtain directly the values of vertex constants only, which in turn are consistent with those determined by extrapolation of the experimental cross sections of the (p, d) reactions to the pole.In the case of (³He, ) reactions, however, the analysis indicates inadequacy of the DWBA concerning the calculations of central partial amplitudes. For a more reliable extraction of structural information, besides the correct normalization of peripheral amplitudes, a contribution of more complex mechanisms must be taken into account.     

Nuclear pumping of a3He-Cs metal-vapor mixture

Results of a spectroscopic study of low temperature atmospheric density³He-Cs plasmas created by the³He(n, p)³T reaction at a thermal neutron flux of about 8×10¹¹ n/cm² s are presented. Measurements were carried out using the steady state nuclear reactor of the Moscow Engineering Physics Institute as a neutron source in the temperature range 70–450°C. The possibility of direct nuclear pumped³He-Cs laser action is indicated by calculations ofnp,ns CsI level populations.     

Low-lying valence and Rydberg states of NS, obtained by configuration-interaction studies

Using double-ζ plus polarization basis sets with diffuse s and p functions on N and S, configuration-interaction calculations were carried out for low-lying valence and Rydberg states of NS. In general, there is good agreement with experimentally obtained spectroscopic constants, and with theoretical results obtained by other groups. The avoided crossing of 2²Σ⁺(C) and 3²Σ⁺(I), and the reported predissociation from low vibrational levels of the C state received particular attention.     

Cross-section measurements and thermonuclear reaction rates for 50Ti(p, γ)51V and 50Ti(p,n)50V

The yields of γ-rays from the reactions ⁵⁰Ti(p, γ)⁵¹V and ⁵⁰Ti(p, p 'γ)⁵⁰Ti have been measured as a function of bombarding energy over the range 0.73–4.39 MeV and the yield of neutrons from the reaction ⁵⁰Ti(p, n)⁵⁰V has been measured from threshold to a bombarding energy of 4.39 MeV. Competition effects were observed in the γ-ray yields from the (p, γ) and (p, pγ) reactions at the threshold of the (p, n) reaction. The observed yields in all channels were lower by factors of order 3 than those predicted by statistical-model calculations based on global optical parameters and the competition observed in the (p, γ) yield at the opening of the neutron channel was approximately one half that predicted by the statistical-model calculations. These failures of the calculations are tentatively attributed to the neutron closed-shell nature of ⁵⁰Ti. Thermonuclear reaction rates for the (p, γ) and (p, n) reactions are calculated for the temperature range (0.6–5) × 10⁹ K which includes the range of temperatures of interest in nucleosynthesis calculations.     

A study of the odd isotopes of copper using the 58, 60, 62, 64Ni(τ, d) 59, 61, 63, 65Cu and 48Ca(τ, d)49Sc reactions

Experimental measurements are reported for the ^{58, 60, 62, 64}Ni(τ, d) ^{59, 61, 63, 65}Cu and ⁴⁸Ca(τ, d)⁴⁹Sc reactions and for the elastic scattering of ³He particles from ^{58, 60, 62, 64}Ni and ⁴⁸Ca targets at an incident energy of 18 MeV. The (τ, d) angular distributions cover the angular range from approximately θ_c.m. = 5° to 90° and the elastic scattering angular distributions range from θ_c.m. = 12° to 172°. In the (τ, d) reactions several weakly excited states, not previously seen in stripping reactions, have been identified and assignments of the transferred angular momentum made. The ⁴⁸Ca(τ, d)⁴⁹Sc reaction data are used in conjunction with the theoretical sum rules of MacFarlane and French to determine the normalization factors to be used with DWBA calculations for different sets of optical potentials. These normalization factors are used to extract spectroscopic strengths and centroid energies from the Ni(τ, d)Cu data which are compared with published model calculations for the odd copper isotopes. It is concluded that these calculations invariably fail to give a consistent picture of the odd copper isotopes mainly due to the use of centroid energies as variable parameters in the model calculations.     

High resolution investigation of 91Mo and 92Mo via (p,d) and (p,t) reactions on 90Mo

The (p, d) and (p, t) reactions on ⁹²Mo have been studied at a proton energy of 28.0 MeV. Using an Enge split-pole spectrograph, resolutions of 11–15 keV for the detected deuterons and tritons were obtained. A total of 87 levels up to 4.9 MeV in ⁹¹Mo and 25 levels up to 4.0 MeV in ⁹⁰Mo were found, several of which were previously unknown. By comparing the measured angular distributions with DWBA calculations l-values and spectroscopic factors were determined. The results are compared with data from previous experiments on ⁹¹Mo and ⁹⁰Mo, with experiments on other N = 49 and 48 nuclei, and with theoretical calculations.     

An accurate and simple method of measuring nuclear spin lattice relaxation at low temperatures,applied to60CoFe

Pulsed eddy current heating of a thin Fe foil, cooled by direct contact with the He within the mixing chamber of a dilution refrigerator, is used to measure the nuclear spin lattice relaxation of dilute⁶⁰Co in Fe. This simple method — which gives the true domain relaxation — avoids several difficulties present in other types of experiments, as is shown in a comparison of methods. The field dependence of the Korringa constant is measured between 0 and 10 kG; above 1 kG it is found to approach exponentially a limiting value of 2.27 sK.     

Transfer reactions induced by 17, 18O on 12, 13C at c.m. energies between 12.6 TO 14.0 MeV

Angular distributions for one-neutron and many-nucleon transfer reactions were measured in the systems ^{17, 18}O and ^{12, 13}C at c.m. energies between 12.6 to 14.0 MeV. All the cross sections were analyzed in terms of the full-recoil finite-range DWBA model. For multi-nucleon transfer processes an inert cluster transfer was assumed. The sensitivity of DWBA calculations to various parameter sets is discussed, and the effect of the no-recoil approximation on the phase and magnitude of the transfer amplitude is studied. For one-neutron transfer reactions the forward part of the angular distributions was reproduced reasonably well by the DWBA model, yielding satisfactory spectroscopic information. The rise of the cross section at the backward angles was not reproduced by the DWBA model. Possible contributions of cluster-exchange and compound-nucleus reactions are discussed. For multi-nucleon transfer reactions poorer fits were obtained, particularly in the ¹⁸O+¹²C system.     

Electro- and photoinduced spallation reactions on27Al and51V at intermediate energies

Cross sections for some electro- and photoinduced spallation reactions on²⁷Al and⁵¹V have been measured in the energy region 130–580 MeV with the activation method. The cross sections per photon are compared to Monte-Carlo calculations based on a cascade-evaporation model. The electrodisintegration cross sections are compared to calculations based on the Dalitz formalism for virtual photon spectra.     

Inelastic scattering and reaction data analysis for the 3He+44,48Ca systems

Analysing-power and cross-section distributions for the inelastic and single-nucleon transfer reactions involving the scattering of 33 MeV polarised helions from ^44,48Ca targets have been measured, and analysed with the DWBA framework. The inelastic scattering distributions are found to be insensitive to the ambiguities in the spin-orbit component of the distorting optical-model potential — which are shown to exist when fitting the elastic data. The deformation length is found to be a better representative of the nuclear shape than the deformation parameter. For the (³$\text{He}$, d) and (³$\text{He}$, α) reactions, both the zero-range and finite-range (within the local-energy approximation) calculations have been carried out and several effects such as the inclusion of non-locality correction, the j-dependence of the distributions, and the sensitivity of the predictions to the entrance- and exit-channel distorting potentials are discussed. The deduced spectroscopic factors are consistently lower than the values reported in the literature by other investigators, although the relative spectroscopic factors are shown to be in good agreement with those of others. The data measured for the charge-exchange reactions, ⁴⁸Ca(³$\text{He}$, t), populating a number of levels in ⁴⁸Sc are also presented.     

The reaction 26Mg(d, τ)25Na and the structure of 25Na

The nuclear structure of the nucleus ²⁵Na has been studied with the (d, τ) proton pick-up reaction on ²⁶Mg at a bombarding energy of 29 MeV with an energy resolution of 25 to 30 keV FWHM. Excited states in ²⁵Na have been measured up to excitation energies of 8 MeV. The experimental angular distributions show good agreement with the predictions from the standard distorted-wave Born-approximation theory (code DWUCK; non-local and finite range). However, the agreement is improved considerably if the procedure of Kunz, Rost and Johnson is applied which accounts approximately for strong couplings to inelastic channels in the initial and final (strongly deformed) nuclei. The influence of this treatment on the evaluation of spectroscopic factors has been investigated and was found to be particularly pronounced for l = 0 transitions. The measured spectroscopic factors are compared to those from other experimental work and from shell-model and Nilsson-model calculations.     

Influence of Prototropic Reactions on the Absorption and Fluorescence Spectra of Methyl p-dimethylaminobenzoate and Its Two Ortho Derivatives

The influence of prototropic reactions on the spectral characteristics of methyl p-dimethylaminobenzoate (I) and its o-methoxy (II) and o-hydroxy (III) derivatives has been studied using steady-state spectroscopic technique and quantum-chemical calculations. This study concerns the solvent-induced shift of the absorption, locally excited (LE) and intramolecular charge transfer (ICT) fluorescence bands in the neat tetrahydrofuran (THF) and its hydrochloric acid solutions at different HCl concentrations. On the basis of the experimental results and quantum-chemical calculations, it was shown that in a hydrochloric acid solution the studied molecules exist as a mixture of neutral, mono-, and dicationic forms. Additionally, the results of spectroscopic measurements were used to calculate, according to the Benesi-Hildebrand method, the equilibrium constants of protopropic reactions in the ground, S ₀, and excited, S ₁, states. Our findings predestine molecules I and II to be used as acid fluorescence probes in a region of 0–2.5 M of [H⁺] concentrations.     

9Be(3He,n)11C and 11B(3He,n)13N Reactions at Energies below Coulomb Barrier

Angular distributions have been measured for ⁹Be(³He, n)¹¹C and ¹¹B(³He, n)¹³N reactions for the neutron group leading to the ground state at E_3He = 0.90, 1.00, 1.20, 1.40 MeV and 1.70, 1.90 MeV respectively. To fit the experimental data, the theory of two nucleon stripping reactions below the Coulomb barrier has been considered. Taking Coulomb distorted wave functions for the interacting particles in the initial channel, a closed analytical form for the differential cross-section has been obtained. The other two cases using the plane wave Born approximation and the distorted wave Born approximation are also applied to the experimental data. The agreement between the Coulomb distorted wave calculations and the experimental data is better than with the PWBA and DWBA. The spectroscopic factors are extracted by fitting the experimental data with the theoretical calculations.     

Finite-range DWBA analysis of (p, α) reactions on Be and B

The ground state angular distributions of the reactions ⁹Be(p, α)⁶Li and ¹¹B(p, α)⁸Be are analyzed by means of the DWBA theory. One-step direct mechanisms only are considered, but for both reactions the inclusion of the heavy-particle pick-up is found to be essential. DWBA fits to the data are obtained (a) in the zero-range approximation, (b) in the “fixed-range” approximation and (c) by an exact finite-range calculation. Only the latter method yields both an acceptable fit and reasonable values for the spectroscopic factors.     

Preequilibrium emission in (p,x n) reactions on palladium isotopes

Energy spectra of neutrons from the^{104, 105, 106, 108, 110}pd(p, xn) reactions atE _p=26.1 MeV have been measured using the time-of-flight technique with good overall energy resolution (< 250=" kev).=" the=" hard=" part=" of=" angle-integrated=" spectra=" corresponding=" to=" low=" residual=" excitations=">U6MeV) exhibits pronounced structure varying from isotope to isotope. The observed structure can be reasonably well described by preequilibrium-model calculations with two-quasiparticle state densities for proton-particle neutron-hole configurations based on Nilsson-model single-particle levels instead of equidistant ones. The influence of nuclear deformation and pairing on preequilibrium particle emission is explored.Supported in part by the exchange program of the Universities of Hamburg and Zagreb, Internationales Büro — KFA Jülich, and by the BMFT (Contract 06 HH 142)     

Cross section measurements of the Pd(p, γ)Ag, Sn(p, γ)Sb, and Sn(α, γ)Te reactions relevant to the astrophysical rp- and γ-processes

Total cross section measurements for the ¹⁰²Pd(p, γ)¹⁰³Ag and ¹¹⁶Sn(p, γ)¹¹⁷Sb reactions have been performed in the proton energy range 2.6 to 4.25 MeV, and for the ¹¹²Sn(α, γ)¹¹⁶Te reaction over the alpha beam energy range 7.0 to 10.5 MeV. An activation technique was used in which gamma rays from decays of the reaction products were detected off-line by two hyper-pure germanium detectors in a low background environment. Where possible, reaction rates are derived and the results compared to those of calculations generated by the NON-SMOKER and the MOST statistical model codes so as to judge their applicability for describing the cross sections needed for network calculations of nucleosynthesis in explosive astrophysical environments via the γ- and rp-processes.