72 research outputs found
Isovector soft dipole mode in 6Be
By using the 1H(6Li,6Be)n charge-exchange reaction, continuum states in 6Be
were populated up to E_t=16 MeV, E_t being the 6Be energy above its three-body
decay threshold. In kinematically complete measurements performed by detecting
alpha+p+p coincidences, an E_t spectrum of high statistics was obtained,
containing approximately ~5x10^6 events. The spectrum provides detailed
correlation information about the well-known 0^+ ground state of 6Be at
E_t=1.37 MeV and its 2^+ state at E_t=3.05 MeV. Moreover, a broad structure
extending from 4 to 16 MeV was observed. It contains negative parity states
populated by Delta L=1 angular momentum transfer without other significant
contributions. This structure can be interpreted as a novel phenomenon, i.e.
the isovector soft dipole mode associated with the 6Li ground state. The
population of this mode in the charge-exchange reaction is a dominant
phenomenon for this reaction, being responsible for about 60% of the cross
section obtained in the measured energy range.Comment: 8 pages, 7 figure
MAYA: An active-target detector for binary reactions with exotic beams
International audienceWith recent improvements in the production of radioactive beams in facilities such as SPIRAL at GANIL, a larger area of the nuclear chart is now accessible for experimentation. For these usually low-intensity and low-energy secondary beams, we have developed the new MAYA detector based on the active-target concept. This device allows to use a relatively thick target without loss of resolution by using the detection gas as target material. Dedicated 3D tracking, particle identification, energy loss and range measurements allow complete kinematic reconstruction of reactions taking place inside MAYA
The He-8 and He-10 spectra studied in the (t,p) reaction
The low-lying spectra of He and He nuclei were studied in the
H(He,)He and H(He,)He transfer reactions. The
ground state (g.s.) of He and excited states, at MeV
and at MeV, were populated with cross sections of 200,
100-250, and 90-125 b/sr, respectively. Some evidence for He state at
about 7.5 MeV is obtained. We discuss a possible nature of the near-threshold
anomaly above 2.14 MeV in He and relate it to the population of a
continuum (soft dipole excitation) with peak value at about 3 MeV. The lowest
energy group of events in the He spectrum was observed at MeV
with a cross section of b/sr. We argue that this result is
possibly consistent with the previously reported observation of He, in
that case providing a new g.s. position for He at about 3 MeV.
Comment: 18 pages, 8 figures, submitted to Phys. Lett.
The He-8 and He-10 spectra studied in the (t,p) reaction
The low-lying spectra of He and He nuclei were studied in the
H(He,)He and H(He,)He transfer reactions. The
ground state (g.s.) of He and excited states, at MeV
and at MeV, were populated with cross sections of 200,
100-250, and 90-125 b/sr, respectively. Some evidence for He state at
about 7.5 MeV is obtained. We discuss a possible nature of the near-threshold
anomaly above 2.14 MeV in He and relate it to the population of a
continuum (soft dipole excitation) with peak value at about 3 MeV. The lowest
energy group of events in the He spectrum was observed at MeV
with a cross section of b/sr. We argue that this result is
possibly consistent with the previously reported observation of He, in
that case providing a new g.s. position for He at about 3 MeV.
Comment: 18 pages, 8 figures, submitted to Phys. Lett.
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