Theoretical study on spherical proton emission

The proton radioactivity half-lives of spherical proton emitters are investigated within a generalized liquid drop model(GLDM),including the proximity effects between nuclei in a neck and the mass and charge asymmetry.The penetrability is calculated in the WKB approximation and the assault frequency is estimated by the quantum mechanism method considering the structure of the parent nucleus.The spectroscopic factor is taken into account in half-life calculation,which is obtained by employing the relativisti...     

Systematic properties of proton single-particle energies

Single-particle energies of protons in the 1f_7/2, 2p_3/2, 2p_1/2, 1f_5/2 and 1g_9/2 shells of medium-weight nuclei were determined from proton pickup and stripping experiments. The data reveal a simple linear dependence on mass number A and isospin T_o of the target nuclei which can be interpreted in terms of an extended Bansal-French model.     

β delayed emission of a proton by a one-neutron halo nucleus

Some one-neutron halo nuclei can emit a proton in a β decay of the halo neutron. The branching ratio towards this rare decay mode is calculated within a two-body potential model of the initial core + neutron bound state and final core + proton scattering states. The decay probability per second is evaluated for the ¹¹Be, ¹⁹C and ³¹Ne one-neutron halo nuclei. It is very sensitive to the neutron separation energy.     

Systematics of proton emission

A very simple formula is presented that relates the logarithm of the half-life, corrected by the centrifugal barrier, with the Coulomb parameter in proton decay processes. The corresponding experimental data lie on two straight lines which appear as a result of a sudden change in the nuclear shape marking two regions of deformation independently of the angular momentum of the outgoing proton. This feature provides a powerful tool to assign experimentally quantum numbers in proton emitters.     

β delayed proton emission from a long-lived high-spin isomer in 95Pd

A long-lived high-spin isometric state in ⁹⁵Pd with a half-life of 14 ± 1s and with $\text{J}{}^{\mathrm{\pi }}\text{≈}\text{21}\text{2}{}^{\mathrm{+}}$ has been identified. It has been found that this state is a β delayed proton precursor. A decay scheme of ⁹⁵Pd has been derived.     

Relativistic effects in proton-induced deuteron break-up at intermediate energies with forward emission of a fast proton pair

Recent data of the reaction with a fast forward pp pair with small excitation energy is analyzed within a covariant approach based on the Bethe-Salpeter formalism. Relativistic effects in cross-section are extracted and found to be large. It is demonstrated that the node of the non-relativistic amplitude is shifted and masked by relativistic effects from Lorentz boost and the negative-energy P components in the ¹S₀ Bethe-Salpeter amplitude of the pp pair.Received: 22 July 2003, Revised: 7 October 2003, Published online: 5 February 2004PACS: 13.75.Cs Nucleon-nucleon interactions (including antinucleons, deuterons, etc.) - 25.10. + s Nuclear reactions involving few-nucleon systemsL.P. Kaptari: On leave of absence from Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna, Russia; also at Department of Physics, Universitá di Perugia, and INFN Sezione di Perugia, via A. Pascoli, I-06100, Italy.Present address S.S. Semikh: Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna, Russia.     

Gamma-ray energies of short-lived Rb,Sr, and Y isotopes indicating delayed neutron emission to excited states

Gamma energies in the level schemes of ^95,96,97Sr, ^95,96,97Y, and ^95,97Zr are reported. Some of their excited levels are populated by delayed neutron emission. These nuclei were produced as daughters of Rb fission fragments originating from the reaction ²³⁵U(n, f). By thermal ionization they were separated from fission products having other nuclear charge states and by an on-line mass separator according to their respective masses.     

A survey of neutron and proton binding energies

Limiting values of last-nucleon binding energies are available from measured reaction energies of induced transformations satisfying the selection rule ΔA=0, ±1 (A=mass number) in about 140 cases. In 14 cases upper and lower limiting values are known separately, and these agree in each case within the limits of experimental error. Taking the other 126 values as ‘true’ (rather than limiting) values, and using information concerning total energies of β-disintegration, the number of last-nucleon binding energies which are reasonably well determined is increased to more than 600. These values are tabulated, and discussed in relation to the v. Weizsäcker mass formula. Apart from certain anomalies which are treated individually, the discussion brings out the effect of α-unit structure in light nuclei, diminishing in importance to become almost negligible beyond A=40, and yields mean values for nucleon-parity dependent terms in the range A～215. The recovery of ‘normal’ last-nucleon binding energy after completion of a closed shell is followed in detail over the range 126ˇ-Nˇ-136 (N=neutron number) and somewhat less closely over the range 82ˇ-Zˇ-92 (Z=proton number).     

Computing the cross sections of nuclear reactions with nuclear clusters emission for proton energies between 30 MeV and 2.6 GeV

The cross sections of nuclear reactions involving emission of clusters of light nuclei in proton collisions with a heavy-metal target are computed for incident-proton energies between 30 MeV and 2.6 GeV. The calculation relies on the ALICE/ASH and CASCADE/INPE computer codes. The parameters determining the pre-equilibrium cluster emission are varied in the computation.     

Beta delayed proton emission from the 14s 21/2+ spin gap isomer in95Pd

The residual activities of the projectile-target system⁴⁰Ca→⁵⁸Ni have been investigated with gamma and proton multi spectrum analyses,γγ andpγ coincidences. Aβ decaying high-spin isomer in⁹⁵Pd withJ ^π=(21/2⁺), a half-life of 14±1 s and an excitation energy of about 2 MeV has been identified. It has been found that⁹⁵Pd ^m is aβ delayed proton precursor. The totalβ branching to proton emitting states has been determined to be (0.74±0.19)·10^?2. It has been observed that the final state in⁹⁴Ru, populated after proton emission, is dominantly the 8⁺ state. A decay scheme of⁹⁵Pd ^m has been derived.     

Unified fission model for proton emission

The unified fission model (UFM) combining with the phenomenological assault frequency has been carried out to investigate the proton-radioactivity half-lives of spherical proton emitters. The results are in good agreement with the experimental data and other theoretical values, and newly observed spherical proton emitters have been analyzed. Finally, the effect of angular momentum transfer on half-life of proton emission has been discussed in detail and a formula can be used to describe this relationship.     

Antiproton and proton energy loss straggling at keV energies

The slowing-down process of point-like charged particles in matter has been investigated by measuring the energy straggling for antiprotons and protons in Al, Ni and Au. A comparison with binary theory shows good agreement for Al and Au. For Ni, experimental data are not as convincing. In particular for the aluminum target, the Barkas-like effect of reduced energy straggling for antiprotons compared to protons is visible in the experimental data and a nearly velocity-proportional straggling is found, in good agreement with binary theory.     

Unified fission model for proton emission

The unified fission model （UFM） combining with the phenomenological assault frequency has been carried out to investigate the proton-radioactivity half-lives of spherical proton emitters. The results are in good agreement with the experimental data and other theoretical values, and newly observed spherical proton emitters have been analyzed. Finally, the effect of angular momentum transfer on half-life of proton emission has been discussed in detail and a formula can be used to describe this relationship.     

A new delayed proton precursor: Chromium-45

The new $\text{T}{}_{\mathrm{z}}\text{= ?}\text{3}\text{2}$ isotope, ⁴⁵Cr, has been produced by the ³²S(¹⁶O, 3n)⁴⁵ Cr reaction. Its half-life was measured to be 50 ± 6 ms. A single β-delayed proton group with center-of-mass energy 2.10 ± 0.05 MeV was observed, corresponding to the decay of the lowest $\text{T}{}_{\mathrm{z}}\text{=}\text{3}\text{2}$ state in ⁴⁵V.     

An analysis of prompt lepton emission at ISR energies

The e/π ratios at low p_T observed in pp collisions at √s = 53 GeV are analysed as a function of R, the ratio of the total number of electrons integrated over electron energies to the total number of pions integrated over pion energies. It is found that R is independent of the decay kinematics and very insensitive to the production dynamics of the parent particles. The total parent cross section times the branching ratio into an electron is calculated, and the result is interpreted as either the total inclusive cross section for production of charmed particles, or as the total cross section for single photons in pp collisions.     

Polarimetry of the polarized proton and deuteron beams at intermediate energies

Method and results of the beam polarization measurements are presented. The measurements were carried out at the proton polarized beam of Saturne-II accelerator as well as at the JINR (Dubna) synchrophasotron vector polarized deuteron beam. The analysis of the elastic (quasi-elastic) pp-scattering polarization is used as a method of the polarization measurements. The energy range of the measurement is 1.0≤T _p ≤2.8 GeV for polarized proton and 1.66≤T _d ≤7.3 GeV for polarized deuteron beams.