Role of dynamical particle-vibration coupling in reconciliation of the d3/2d_{3/2} puzzle for spherical proton emitters

It has been observed that decay rate for proton emission from $d_{3/2}$ single particle state is systematically quenched compared with the prediction of a one dimensional potential model although the same model successfully accounts for measured decay rates from $s_{1/2}$ and $h_{11/2}$ states. We reconcile this discrepancy by solving coupled-channels equations, taking into account couplings between the proton motion and vibrational excitations of a daughter nucleus. We apply the formalism to proton emitting nuclei $^{160,161}$Re to show that there is a certain range of parameter set of the excitation energy and the dynamical deformation parameter for the quadrupole phonon excitation which reproduces simultaneously the experimental decay rates from the 2$d_{3/2}$, 3$s_{1/2}$ and 1$h_{11/2}$ states in these nuclei.Comment: RevTex, 12 pages, 4 eps figure

Strength of the 18F(p, α)15O resonance at Ec.m. = 330 keV

The astrophysical rate of the 18F(p,α)15O reaction at nova temperatures is critical to understanding production of the radioisotope 18F, which may be used to constrain nova models via observations with the coming generation of satellite-based γ-ray telescopes. As such, a measurement is made of the strength of this resonance using a radioactive 18F beam at the HRIBF. As a result, it is indicated that the 18F(p,α)15O reaction rate is lower than previous estimates by a factor of ∼2

Theoretical description of deformed proton emitters: nonadiabatic coupled-channel method

The newly developed nonadiabatic method based on the coupled-channel Schroedinger equation with Gamow states is used to study the phenomenon of proton radioactivity. The new method, adopting the weak coupling regime of the particle-plus-rotor model, allows for the inclusion of excitations in the daughter nucleus. This can lead to rather different predictions for lifetimes and branching ratios as compared to the standard adiabatic approximation corresponding to the strong coupling scheme. Calculations are performed for several experimentally seen, non-spherical nuclei beyond the proton dripline. By comparing theory and experiment, we are able to characterize the angular momentum content of the observed narrow resonance.Comment: 12 pages including 10 figure

Neutron single particle strengths from the (d,p) reaction on F18

The F19 nucleus has been studied extensively. However, there have been no comprehensive experimental studies of F18+n single-particle components in F19, and no measure of neutron vacancies in the F18 ground state, as such experiments require a (radioactive) F18 target or beam. We have used the H2(F18,p)F19 reaction to selectively populate states in F19 that are of F18+n character. The 108.5-MeV radioactive F18+9 beam was provided by the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. Proton-recoil coincidence data were taken for both α-decaying and particle-stable final states. Angular distributions and spectroscopic factors were measured for nine proton groups, corresponding to 13 states in F19. The results are compared to shell model calculations

New constraints on the18F(p,α)15O rate in novae from the (d, p) reaction

The degree to which the (p,γ) and (p,α) reactions destroy 18F at temperatures (1-4) × 108 K is important for understanding the synthesis of nuclei in nova explosions and for using the long-lived radionuclide 18F, a target of γ-ray astronomy, as a diagnostic of nova mechanisms. The reactions are dominated by low-lying proton resonances near the I8F+p threshold (Ex = 6.411 MeV in 19Ne). To gain further information about these resonances, we used a radioactive 18F beam from the Holifield Radioactive Ion Beam Facility to selectively populate corresponding mirror states in 19F via the inverse 2H(18F,p)19F neutron transfer reaction. Neutron spectroscopic factors were measured for states in 19F in the excitation energy range 0-9 MeV. Widths for corresponding proton resonances in 19Ne were calculated using a Woods-Saxon potential. The results imply significantly lower I8F(p,γ)19Ne and I8F(p,α)15O reaction rates than reported previously, thereby increasing the prospect of observing the 511 keV annihilation radiation associated with the decay of 18F in the ashes ejected from novae

Prolate yrast cascade in 183Tl

The yrast sequence in 183Tl has been studied for the first time in recoil-mass selected γ-ray spectroscopic measurements. A rotational-like cascade of seven transitions is established down to the band head with probable spin and parity (13/2+). Unlike in the adjacent odd-mass Tl nuclei, prompt γ decay from the yrast band to a lower lying weakly deformed (oblate) structure is not observed. These features are consistent with the predicted drop of the prolate band head in 183Tl compared to 185Tl. The implications for the prolate energy minimum in odd-mass Tl nuclei at the neutron i 13/2 midshell (N = 103) are discussed

Triaxiality near the 110Ru ground state from Coulomb excitation

A multi-step Coulomb excitation measurement with the GRETINA and CHICO2 detector arrays was carried out with a 430-MeV beam of the neutron-rich 110Ru (t1/2=12 s) isotope produced at the CARIBU facility. This represents the first successful measurement following the post-acceleration of an unstable isotope of a refractory element. The reduced transition probabilities obtained for levels near the ground state provide strong evidence for a triaxial shape; a conclusion confirmed by comparisons with the results of beyond-mean-field and triaxial rotor model calculations

Behavior of intruder based states in light Bi and Tl isotopes: the study of {sup 187 Bi} {alpha} decay

Intruder state excitation energies in odd-mass nuclei just outside a closed proton shell plotted versus neutron number generally exhibit parabola-shaped curves with minima near neutron mid-shells. The Bi isotopes, however, do not seem to follow this trend. Recent experiments performed at Argonne National Laboratory have identified the previously unobserved {sup 187}Bi ground state (h{sub 9/2}) to {sup 183}TI ground state s{sub 1/2} {alpha} transition. Its energy when combined with those of two earlier known transitions, namely {sup 187}Bi (h{sub 9/2}) {yields} {sup 183m}Tl (h{sub 9/2}) and {sup 187m}Bi (s{sub 1/2}) {yields} {sup 183}Tl(s{sub 1/2}), establishes the excitation energies of the {sup 183m}Tl and {sup 187m}Bi to be 620(20) keV and 110(20) keV, respectively. This value for {sup 187m}Bi is 80 keV lower than the excitation energy of the same intruder level in {sup 189}Bi. Implications of this result with respect to intruder-state systematics are discussed