Speaker
Mr.
Pavel Sharov
(Joint Institute for Nuclear Research)
Description
Structure of nuclei located near and beyond the drip-lines plays important role
in the explosive astrophysical processes.
The problem of two-proton decay of the $^{17}$Ne first excited state is a good example of such situation.
The two-proton radiative capture is a possible bypass of the $^{15}$O waiting point in the rp-process.
The rate of this process drastically depends on the $2p/\gamma$ branching ratio
of the $^{17}$Ne first excited state.
The first excited state of $^{17}$Ne (with $J^\pi = 3/2^{-}$) is located only 344 keV above
the 2p decay threshold, and its $2p$ decay partial width is much less then the gamma-decay partial width.
The existing experimental threshold for the $2p/\gamma$ ratio (0.77 %) [1] is a few orders of magnitude greater
than theoretical predictions made for this value (2.5e-6)[2].
Experiments aimed at the measuring such low branching ratio require
development of special methods.
In the recent experiment at the ACCULINNA [3] fragment-separator (Flerov Lab. JINR)
the two-proton decay of the low-lying states of $^{17}$Ne populated in the
$p(^{18}$Ne$,d)^{17}$Ne transfer reaction were studied.
Original combined-mass method was used in the experiment.
This method allows to get relatively good energy resolution ($\sigma\sim 130$ keV) without serious restriction on luminosity.
As result, new $2p/\gamma$ ratio threshold for the $^{17}$Ne $3/2^{-}$ state equal 0.016(3)% was achieved, that is about fifty times less than existing value.
The proposed method is promising for the study of the searched $2p$ decay partial width at level of
$\Gamma_{2p}/\Gamma_\gamma \approx 10^{-6}$
[1] [M. J. Chromik, et. al., Phys.Rev. C55 (2002) 024313]
[2] [L. V. Grigorenko, M. V. Zhukov, Phys.Rev. C76 (2007) 014008]
[3] http://aculina.jinr.ru/
Primary authors
Dr.
Andrey Fomichev
(Joint Institute for Nuclear Research)
Prof.
Gurgen Ter-Akopian
(Joint Institute for Nuclear Research)
Prof.
Leonid Grigorenko
(Joint Institute for Nuclear Research)
Prof.
Mikhail Golovkov
(Joint Institute for Nuclear Research)
Mr.
Pavel Sharov
(Joint Institute for Nuclear Research)
