3 research outputs found
Improved precision on the experimental E0 decay branching ratio of the Hoyle state
Stellar carbon synthesis occurs exclusively via the process, in
which three particles fuse to form C in the excited Hoyle
state, followed by electromagnetic decay to the ground state. The Hoyle state
is above the threshold, and the rate of stellar carbon production
depends on the radiative width of this state. The radiative width cannot be
measured directly, and must instead be deduced by combining three separately
measured quantities. One of these quantities is the decay branching ratio
of the Hoyle state, and the current \% uncertainty on the radiative width
stems mainly from the uncertainty on this ratio. The branching ratio was
deduced from a series of pair conversion measurements of the and
transitions depopulating the Hoyle state and state in C,
respectively. The excited states were populated by the C
reaction at 10.5 MeV beam energy, and the pairs were detected with the
electron-positron pair spectrometer, Super-e, at the Australian National
University. The deduced branching ratio required knowledge of the proton
population of the two states, as well as the alignment of the state in
the reaction. For this purpose, proton scattering and -ray angular
distribution experiments were also performed. An branching ratio of
was deduced in the current work,
and an adopted value of is
recommended based on a weighted average of previous literature values and the
new result. The new recommended value for the branching ratio is about 14%
larger than the previous adopted value of
, while the uncertainty has been
reduced from 9% to 5%.Comment: Accepted for publication as a Regular Article in Phys. Rev. C on July
29 202
E0 transition strength in stable Ni isotopes
Excited states in 58,60,62Ni were populated via inelastic proton scattering at the Australian National University as well as via inelastic neutron scattering at the University of Kentucky Accelerator Laboratory. The Super-e electron spectrometer and the CAESAR Compton-suppressed HPGe array were used in complementary experiments to measure conversion coefficients and δ(E2/M1) mixing ratios, respectively, for a number of 2+→2+ transitions. The data obtained were combined with lifetimes and branching ratios to determine E0,M1, and E2 transition strengths between 2+ states. The E0 transition strengths between 0+ states were measured using internal conversion electron spectroscopy and compare well to previous results from internal pair formation spectroscopy. The E0transition strengths between the lowest-lying 2+ states were found to be consistently large for the isotopes studied
First-excited state g factors in the stable, even Ge and Se isotopes FIRST-EXCITED STATE g FACTORS in the ... B. P. McCORMICK et al.
International audienceTransient-field -factor measurements in inverse kinematics were performed for the first-excited states of the stable, even isotopes of Ge and Se. The factors of Ge and Se were measured simultaneously using a cocktail beam, which eliminates most possible sources of systematic error in a relative -factor measurement. The results are , , , , , , and . The measured -factor ratios are in agreement with ratios from previous measurements, despite considerable variation in previous reported absolute values. The absolute values of the factors remain uncertain, however the Rutgers parametrization was used to set the transient-field strength and then compare the experimental factors with shell-model calculations based on the JUN45 and jj44b interactions. Modest agreement was found between experiment and theory for both interactions. The shell model calculations indicate that the values and trends are determined largely by the balance of the spin carried by orbital motion of the protons