Triaxial projected shell model study of chiral rotation in odd-odd nuclei

Chiral rotation observed in ¹²⁸Cs is studied using the newly developed microscopic triaxial projected shell model (TPSM) approach. The observed energy levels and the electromagnetic transition probabilities of the nearly degenerate chiral dipole bands in this isotope are well reproduced by the present model. This demonstrates the broad applicability of the TPSM approach, based on a schematic interaction and angular-momentum projection technique, to explain a variety of low- and high-spin phenomena in triaxial rotating nuclei.     

Binding energies of even-even superheavy nuclei in a semi-microscopic approach

The structure of some even-even superheavy nuclei with the proton number Z = 98?120 is studied using a semi-microscopic but not self-consistent model. The macroscopic energy part is obtained from the Skyrme nucleon-nucleon interaction in the semi-classical extended Thomas-Fermi approach. A simple but accurate method is derived for calculating the direct part of the Coulomb energy. The microscopic shell plus pairing energy corrections are calculated from the traditional Strutinsky method. Within this semi-microscopic approach, the total energy curves with the quadrupole deformation of the studied superheavy nuclei were calculated. The same approach features the well known ²⁰⁸Pb or ²³⁸U nuclei. For each nucleus the model predictions for the binding energy, the deformation parameters, the half-density radii and comparison with other theoretical models are made. The calculated binding energies are in good agreement with the available experimental data.     

Nonadiabatic corrections to the rotational energies of the hydrogen molecule

Nonadiabatic corrections to the rotational energies and rotational constants B_ν have been computed by a variational perturbation method for several vibrational levels of the H₂, HD, and D₂ molecules. It is believed that the convergence error in the computed corrections to the energy is less than 10^?3 cm^?1. The corrections improve the agreement of theoretical and experimental rotational quanta, but there are still discrepancies that amount in some cases to a few hundredths of a cm^?1. These discrepancies are irregular and it is argued that they are at least partly due to experimental inaccuracies.     

Projected Shell Model Description of Positive Parity Band of <Superscript>130</Superscript>Pr Nucleus

Theoretical investigation of positive parity yrast band of odd-odd ¹³⁰Pr nucleus is performed by applying the projected shell model. The present study is undertaken to investigate and verify the very recently observed side band in ¹³⁰Pr theoretically in terms of quasi-particle (qp) configuration. From the analysis of band diagram, the yrast as well as side band are found to arise from two-qp configuration πh _11/2???νh _11/2. The present calculations are viewed to have qualitatively reproduced the known experimental data for yrast states, transition energies, and B(M1) / B(E2) ratios of this nucleus. The recently observed positive parity side band is also reproduced by the present calculations. The energy states of the side band are predicted up to spin 25⁺, which is far above the known experimental spin of 18⁺ and this could serve as a motivational factor for future experiments. In addition, the reduced transition probability B(E2) for interband transitions has also been calculated for the first time in projected shell model, which would serve as an encouragement for other research groups in the future.     

Microscopic and macroscopic DWBA analysis of the reactions 28Si(α, d)30P, 32S(d, α)30P and 32S(α, d)34Cl studied at Eα = 50MeV and Ed = 40MeV

The reactions ²⁸Si(α, d)³⁰P, ³²S(d, α)³⁰P and ³²S(α, d)³⁴Cl have been studied at E_α = 50 MeVand E_d = 40 MeV. The angular distributions have been analysed in terms of the single-step, zero-range DWBA with microscopic as well as macroscopic form factors. By requiring an almost identical shape in the microscopic and macroscopic radial form factors for all L-values with L ? 6 the size parameters of the Woods-Saxon well in which the transferred cluster is bound to the nucleus were determined as r₀ = 1.15 fmanda = 0.76 fm. Despite the differences between the two approaches with these parameters the shape of the microscopic angular distribution is well reproduced and the corresponding strengths agree to within 25%. The method has been applied to the three reactions and relative two-nucleon spectroscopic factors have been deduced. A comparison is made with the results of two shell-model calculations.     

Competition between the fusion-fission and deep-inelastic orbiting mechanisms in the35Cl +12C reaction

The binary decay properties of the⁴⁷V nucleus, produced in the³⁵Cl +¹²C reaction, have been investigated at the³⁵Cl bombarding energiesE _lab = 180 and 200 MeV by means of a kinematical coincidence technique. Binary reaction products show full energy equilibration and a characteristic 1/sin(θ _cm) angular distribution. The elemental distribution of the fully-damped products is asymmetric, similar to what has previously been observed in the decay of the⁵⁶Ni nucleus. Comparison with theoretical model predictions suggests the occurrence of a fusion-fission rather than orbiting process. Moreover the calculations performed using the Extended Hauser-Feshbach Method reproduce well the experimental fission yields. A general discussion of orbiting and fusionfission experimental data of light heavy-ion systems is presented in the framework of the calculated number of available open channels for these systems.     

First high-resolution analysis of the 5ν3 band of nitrogen dioxide near 1.3 μm

The first high-resolution absorption spectrum of the 5ν₃ band of the ¹⁴N¹⁶O₂ molecule at 7766.071 cm^?1 was recorded by high sensitivity CW-Cavity Ring Down Spectroscopy between 7674 and 7795 cm^?1. The noise equivalent absorption of the recordings was α_min≈1×10^?10 cm^?1. The assignments involve energy levels of the (0,0,5) vibrational state with rotational quantum numbers up to K_a=9 and N=47. The set of the spin–rotation energy levels were reproduced within their experimental uncertainty using a theoretical model, which takes explicitly into account the Coriolis interactions between the spin rotational levels of the (0,0,5) vibrational state and those of the (0,2,4) dark state together with the electron spin–rotation resonances within the (0,0,5) and (0,2,4) states. Precise values were determined for the (0,0,5) vibrational energy rotational, spin-rotational constants and for the (0,2,4)?(0,0,5) coupling constants. In addition the (0,2,4) rotational and spin-rotational constants were estimated. Using these parameters and the value of the transition dipole moment operator determined from a fit of a selection of experimental line intensities, the synthetic spectrum of the 5ν₃ band was generated and is provided as Supplementary material.     

First high-resolution analysis of the 4ν1+ν3 band of nitrogen dioxide near 1.5 μm

The high-resolution absorption spectrum of the 4ν₁+ν₃ band of the ¹⁴N¹⁶O₂ molecule was recorded by CW-Cavity Ring Down Spectroscopy between 6575 and 6700 cm⁻¹. The assignments involve energy levels of the (4,0,1) vibrational state with rotational quantum numbers up to K_a=8 and N=48. A large majority of the spin-rotation energy levels were reproduced within their experimental uncertainty using a theoretical model which takes explicitly into account the Coriolis interactions between the spin-rotational levels of the (4,0,1) vibrational state and those of the (4,2,0) and of (0,9,0) dark states, the anharmonic interactions between the (4,2,0) and (0,9,0) states together with the electron spin-rotation resonances within the (4,0,1), (4,2,0) and (0,9,0) states. Precise vibrational energies, rotational, spin-rotational, and coupling constants were determined for the {(4,2,0), (0,9,0), (4,0,1)} triad of interacting states. Using these parameters and the value of the transition dipole-moment operator determined from a fit of a selection of experimental line intensities, the synthetic spectrum of the 4ν₁+ν₃ band was generated and is provided as Supplementary Material.     

Comparison of the fusion reactions12C+20Ne and16O+16O near the Coulomb barrier

The partial cross sections of heavy residual nuclei produced in the heavy ion fusion of¹²C+²⁰Ne have been measured atE _c.m.=6–15 MeV viaγ-ray spectroscopy with a Ge(Li) detector. Windowless and recirculating gas target systems have been used. The dominant residual nuclei are²⁴Mg,²⁷Al,²⁸Si,³⁰Si,³⁰P and³¹P, which arise from two- and three-body breakups in the exit channels. The observed excitation functions are smooth in their energy dependence and give no indications for the existence of pronounced resonance structures, in contrast to theoretical predictions. The Coulomb excitation of²⁰Ne served as an intrinsic calibration standard in the determination of absolute partial and total fusion cross sections. The same experimental set-up was also used in the reaction studies of¹⁶O+¹⁶O atE _c.m.=7–14 MeV, going through the same compound nucleus³²S at similar excitation energies. The observed energy dependence in the excitation functions is in good agreement with previous work. The total fusion cross section agrees fairly well with two sets of values reported previously, but deviates significantly from other reported absolute cross section values. The relative evaporation distributions of the residual nuclei are similar for both heavy ion reactions. However, the ratio of their total fusion cross sections deviates from model predictions and suggests that compound nucleus formation does depend on the microscopic structure of the colliding nuclei in the entrance channel. From the observed energy dependence of the above ratio, particularly at subcoulomb energies, geometrical effects in the entrance channel (due to deformed and spherical nuclei) appear to be weak. The astrophysical aspects of the data in the context of late stellar nucleosynthesis are discussed.     

In-beam spectroscopy of231Pa

Information on energy levels and onE 2 andM 1 matrix elements in²³¹Pa has been obtained using conversion-electron and gamma-ray spectroscopy following the²³²Th(p, 2n)²³¹Pa reaction and Coulomb excitation of the radioactive target²³¹Pa by⁴He and³²S ions. The results are analyzed in the framework of the rotational model, applied to the rotational band built on the 1/2^?[530] Nilsson state whose 3/2^? member forms the ground state of this nucleus. The deviations of the level energies from the rigid-rotor values can be described by Coriolis couplings. The analysis of the Coulomb-excitation process shows that a constant set of rotational parameters Q₀, g_R, g_K, andb can fairly well account for the measured line intensities.     

Consistency tests of Ampcalculator and chiral amplitudes in SU(3) Chiral Perturbation Theory: A tutorial-based approach

The positive-parity yrast bands of ^{79, 81, 83, 85, 87, 89}Y isotopes have been studied using the projected shell model (PSM). Nuclear-structure properties like yrast spectra, transition energies, band diagrams, kinetic moment of inertia, rotational frequencies and reduced transition probabilities (B(M1) and B(E2) are calculated. The results obtained from the PSM calculations are also compared with the available experimental as well as theoretical data and, in general, a reasonable agreement is obtained between them. Calculations in the present work also predict that these isotopes have multi-quasiparticle structure.     

Dynamical analysis of dissipative collisions between Ar and Ag nuclei in the fermi energy domain

⁴⁰Ar+¹⁰⁷ Ag reactions at 27 AMeV and 44AMeV have been studied within the Landau Vlasov microscopic transport model. In this framework the main characteristics of primary partners of binary collisions are shown to be well described, and information aboutσ _nn can be extracted as well as the angular momentum associated with the heavy fragment. Different contributions to the total energy are studied as a function of the reaction time. Our numerical method is compared with the results obtained using experimental techniques like proton spectra. Their impact parameter and energy dependences have been studied and the estimated “temperature parameter” is in agreement with the experimental results.     

Equilibrium structure of protonated cyanogen, HNCCN

The cubic force field of protonated cyanogen, HNCCN⁺, has been calculated at the CCSD(T) level of theory employing correlation consistent bases of quadruple-zeta quality. Semi-experimental equilibrium structures have then been derived from the experimental ground-state rotational constants available for various isotopologues and the corresponding vibrational corrections calculated from the theoretical force fields. While a good agreement has been found with the pure theoretical best estimate of equilibrium geometry, computed at the CCSD(T) level of theory accounting for basis set truncation as well as including core correlation corrections, large discrepancies have been noted with the experimental substitution, r_s, as well as effective, r₀, structures.     

The proton strength distribution of the 1g 9/2 state of41Sc

The distribution of the 1g _9/2 proton state of the⁴¹Sc has been obtained within the framework of the coreparticle coupling model scheme. The theoretical distribution pattern of this high-spin proton orbital has been compared with the recent high resolution experimental works performed on the⁴⁰Ca target nucleus. The results obtained in the work has also been compared with the other existing theoretical results.     

Microscopic and macroscopic aspects of 135 MeV proton scattering from 16O

Differential cross sections have been measured for the scattering of 135 MeV protons from ¹⁶O and data from the transitions to 13 states (up to 19.5 MeV excitation) have been analysed using microscopic and macroscopic nuclear reaction models. Extensive collective model calculations have been made of the transitions to all natural-parity states. The deformation parameters for the 4p4h rotational band are in good agreement with theoretical models. The inelastic scattering data from the excitation of the negative-parity states have also been analysed in the distorted-wave approximation using microscopic (shell and RPA) models of nuclear structure and with density-dependent two-nucleon t-matrices. For positive-parity states, we report the first shell-model calculation using the complete 2?ω basis space and find that the triplet of 2p2h states (4⁺, 2⁺, 0⁺) around 11 MeV excitation is quite well described by this model, as may be a 1⁺ state which is observed for the first time by proton scattering from ¹⁶O.     

High-resolution study of 0+ and 2+ excitations in 168Er with the (p, t) reaction

Excited states in the deformed nucleus ¹⁶⁸Er have been studied with high energy resolution in the (p, t) reaction, with the Munich Q3D spectrograph. A large number of excited 0⁺ states (25) and 2⁺ states (64) have been assigned up to 4.0-MeV excitation energy. This allows detailed investigations along two directions of current interest: first, an extension of microscopic model interpretations into the region of medium level density above the pairing gap; second, a first analysis of the statistical fluctuation (order/chaos) properties of pure sequences of levels, in one deformed nucleus. Predictions of two models (the quasiparticle-phonon model and the projected shell model) are compared to the data, and it is concluded that, in both cases, mixing of more configurations is required in the wave functions. The text was submitted by the authors in English.     

Total cross sections for 4,6He + 28Si reactions measured at 10–28 MeV/A

New results on the energy dependence of the total cross section (σ _R) for ⁶He scattering on ²⁸Si in the incident energy range 10–28 MeV/A are obtained. The α-particle-production cross sections for the ²⁸Si(⁶He, ⁴He)X channel are measured as well. The secondary beam of ⁶He with an intensity of up to 5×10⁴ particle/s was generated by bombarding a thick beryllium target with ～32-MeV/A ⁷Li ions. In the energy region below 17 MeV/A, σ _R increases sharply. The experimental dependences of the total cross sections are compared with the results of σ _R calculations using the double-folding potential within the optical model. The energy dependence of σ _R for ⁶He differs from that for the neighboring nuclei, which can be associated with the structural features of the former nucleus. The energy spectra of α particles produced in the ⁶He interactions with silicon indicate two mechanisms of their production: transfer reaction and ⁶He breakup in the field of the ²⁸Si nucleus.