Search

The calcium isotopes are an ideal system to investigate the evolution of shell structure and magic numbers. Although the properties of surface nucleons in calcium have been well studied, probing the structure of deeply bound nucleons remains a challenge. Here, we report on the first measurement of unbound states in 53Ca and 55Ca, populated from 54,56Ca(p,pn) reactions at a beam energy of around 216 MeV/nucleon at the RIKEN Radioactive Isotopes Beam Factory. The resonance properties, partial cross sections, and momentum distributions of these unbound states were analyzed. Orbital angular momentum l assignments were extracted from momentum distributions based on calculations using the distorted wave impulse approximation (DWIA) reaction model. The resonances at excitation energies of 5516(41)keV in 53Ca and 6000(250)keV in 55Ca indicate a significant l =3 component, providing the first experimental evidence for the ν0f7/2 single-particle strength of unbound hole states in the neutron-rich Ca isotopes. The observed excitation energies and cross-sections point towards extremely localized and well separated strength distributions, with some fragmentation for the ν0f7/2 orbital in 55Ca. These results are in good agreement with predictions from shell-model calculations using the effective GXPF1Bs interaction and ab initio calculations and diverge markedly from the experimental distributions in the nickel isotones at Z=28.

The behavior of a quantum particle in an almost infinite deep potential is investigated. By means of analytical and numerical methods, it is demonstrated that even if the potential is infinitely deep, the particle's eigenstate can still be unbound, which contradicts the previous belief that an infinite deep potential can only sustain bound states. These findings shed new light on the eigenstate problem of quantum mechanics. [ABSTRACT FROM AUTHOR]

The calcium isotopes are an ideal system to investigate the evolution of shell structure and magic numbers. Although the properties of surface nucleons in calcium have been well studied, probing the structure of deeply bound nucleons remains a challenge. Here, we report on the first measurement of unbound states in 53Ca and 55Ca, populated from 54,56Ca(p , p n) reactions at a beam energy of around 216 MeV/nucleon at the RIKEN Radioactive Isotopes Beam Factory. The resonance properties, partial cross sections, and momentum distributions of these unbound states were analyzed. Orbital angular momentum l assignments were extracted from momentum distributions based on calculations using the distorted wave impulse approximation (DWIA) reaction model. The resonances at excitation energies of 5516(41) keV in 53Ca and 6000(250) keV in 55Ca indicate a significant l = 3 component, providing the first experimental evidence for the ν 0 f 7 / 2 single-particle strength of unbound hole states in the neutron-rich Ca isotopes. The observed excitation energies and cross-sections point towards extremely localized and well separated strength distributions, with some fragmentation for the ν 0 f 7 / 2 orbital in 55Ca. These results are in good agreement with predictions from shell-model calculations using the effective GXPF1Bs interaction and ab initio calculations and diverge markedly from the experimental distributions in the nickel isotones at Z = 28. [ABSTRACT FROM AUTHOR]

Intense and purified radioactive beam of post-accelerated 14O was used to study the low-lying states in the unbound 15F nucleus. Exploiting resonant elastic scattering in inverse kinematics with a thick target, the second excited state, a resonance at ER=4.757(6)(10) MeV with a width of Γ=36(5)(14) keV was measured for the first time with high precision. The structure of this narrow above-barrier state in a nucleus located two neutrons beyond the proton drip line was investigated using the Gamow Shell Model in the coupled channel representation with a 12C core and three valence protons. It is found that it is an almost pure wave function of two quasi-bound protons in the 2s1/2 shell.

High temperature thermochemistry of the BBr molecule is investigated with the classical approach in the temperature range of 300–20,000 K. The role of ro-vibrational coupling is elucidated. The internal partition function, thermal energy, heat capacity, and entropy are calculated at three levels of approximation, i.e. taking into account bound states on the ground state ( 1 Σ ), including also two excited states ( 3 Π and 1 Π ), and finally adding the resonance and scattering states. The influence of these approximations on studied quantities is investigated. The entropy is found to be the least sensitive to approximations in the ro-vibrational coupling and the heat capacity the most sensitive. [ABSTRACT FROM AUTHOR]

Intense and purified radioactive beam of post-accelerated 14 O was used to study the low-lying states in the unbound 15 F nucleus. Exploiting resonant elastic scattering in inverse kinematics with a thick target, the second excited state, a resonance at E R = 4.757 ( 6 ) ( 10 ) MeV with a width of Γ = 36 ( 5 ) ( 14 ) keV was measured for the first time with high precision. The structure of this narrow above-barrier state in a nucleus located two neutrons beyond the proton drip line was investigated using the Gamow Shell Model in the coupled channel representation with a 12 C core and three valence protons. It is found that it is an almost pure wave function of two quasi-bound protons in the 2 s 1 / 2 shell. [ABSTRACT FROM AUTHOR]

Abstract: A Gamow–Teller (GT) transition from the drip-line nucleus 14Be to 14B was studied via the reaction in inverse kinematics using a secondary 14Be beam at 69 MeV/nucleon. The invariant mass method is employed to reconstruct the energy spectrum. A peak is observed at an excitation energy of 1.27(2) MeV in 14B, together with bumps at 2.08 and 4.06(5) MeV. The observed forward peaking of the state at 1.27 MeV and a good description for the differential cross section, obtained with a DWBA calculation provide support for the assignment to this state. By extrapolating the cross section to zero momentum transfer the GT-transition strength is deduced. The value is found to compare well with that reported in a β-delayed neutron emission study. [Copyright &y& Elsevier]

Correlation functions measured in heavy-ion collisions are used to extract information about the space-time extent of the emitting sources. Similar techniques can be applied to study some spectroscopic properties of unbound states produced during the dynamical evolution of the colliding system. [ABSTRACT FROM AUTHOR]

• Analytical expressions for potential energy curves of OH− ion were calculated. • High temperature partition function was calculated and compared with available data. • High temperature heat capacity was calculated and compared with available data. First principles study of the partition function and heat capacity of OH− anion is conducted at high temperatures (2000 K–10,000 K). Firstly, the quantum chemical ab initio methods (RASSCF with CASPT2 correction) were used to calculate potential energy curves of the ground and excited electronic states; the energy points were fitted to analytical representation of the curves. Secondly, the statistical thermodynamics calculations with the classical method with the quantum Wigner-Kirkwood correction were performed to obtain partition function and heat capacity. Thermochemical tables and data sets usually give quantities up to 6000 K (sometimes even more) and often are not reliable at the highest temperatures, it is shown that in particular electronic excited states could be missing. Partition function is compared with the only available Barklem and Collet data set. Discrepancies between heat capacity data (given in NIST-JANAF and Burcat databases) are pointed out - the inclusion of excited electronic states is crucial. [ABSTRACT FROM AUTHOR]