Authors: J.H. Kelley, G.C. Sheu |  Citation: ENSDF |  Cutoff date: 16-Jan-2016 

 Full ENSDF file | Adopted Levels (PDF version) 

Q(β-)=23.418×103 keV 25S(n)= -82 keV 33S(p)= 19.99×103 keV SYQ(α)= -14.23×103 keV 29
Reference: 2012WA38

  A  9Be(17C,16B)  B  C(17B,N15B)
  C  C(17C,N15B)  D  14C(14C,12N)

General Comments:

The particle instability of 16B:

1974Bo05: Spallation products induced by 4.8 GeV Bevatron protons on a uranuim target were analyzed and identified using standard techniques. The measurement was carried out inside a 91 cm diameter scattering chamber, where the ΔE detector was placed 17 cm from the spallation target and the E detector was 12 cm from the ΔE detector. The time-of-flight between signals in the ΔE and E detectors was measured, and particle identifications were made using ΔE vs E and ΔE vs ToF techniques. The particle instability, limited by the flight time between the ΔE and E detectors, was shown by the lack of observation of any 16B counts along with the positive observation of the neighboring 15B and 17B nuclides.

1985La03: The particle instability of 16B was confirmed at GANIL in a study of the nuclides produced in the fragmentation of a 44 MeV/nucleon 40Ar beam on a thick tantalum target. The fragments were momentum analyzed in the LISE spectrometer, with a 18 meter flight path, and then detected using a ΔE-ΔE-E-VETO telescope at the focal plane. The 13,14,15,17B isotopes were identified in the measurement, but the absence of 16,18B isotopes provide evidence that they are not particle stable (within the limits of the short flight path).

1996Kr05: The authors analyzed the experimental conditions of prior studies and estimated lifetime limits of ≈9 ns (1974Bo05) and ≈260 ns (1985La03). With the aim on better constraining the 16B lifetime, a new experiment was carried out that reached an upper limit of T<170 ps for 16B.

An 880 MeV 17C beam was produced using the NSCL/A1200 fragment separator. The beam was identified by ΔE vs time-of-flight techniques immediately before impinging on a 114 mg/cm2 natC target. Reaction products were stopped in a four element ΔE-ΔE-ΔE-E Si detector telescope that was placed immediately behind the secondary target and covered θ<15|’. No peak corresponding to 16B events was observed in the spectrum, and a limit of T<170 ps 69 was suggested. α significant discussion on "background " events was given in the text.

2013Th07: The authors suggest two novel techniques for measuring lifetimes of neutron unbound nuclides.

Decay in Target: An analysis of the average velocity difference of neutrons vs. charged "core " fragments is suggested as an approach to determine a difference in energy loss in the target that can give average lifetime information.

Decay in Magnetic Field: For relatively long-lived neutron unbound nuclides, if the decaying nuclides are introduced into a dipole magnetic field the average deflection of the neutron yield away from 0|’ could be correlated with the lifetime.

Theoretical analysis:

1985Po10: The binding energies of the four lowest 16B states were predicted in a shell model calculation. The ground state was predicted near the neutron binding threshold with Jπ=0-; excited states were predicted at Ex=0.95, 1.1, 1.55 MeV having Jπ=2-, 3-, 4-, respectively.

1992Wa22: Shell-model calculations in an s, p, sd, f, p valence space predicted a Jπ=0- ground unbound by 164 keV, with Jπ=3-, 2- and 4- excited states at Ex=0.78, 0.84 and 1.44 MeV, respectively.

2011Du01, 2011Du16: An extended two-cluster model predicts a Jπ=0- resonance near the E(15β+n)res≈80 keV state presently identified as the ground state, but also suggests the existence of other Jπ=1-, 2- states that may be closer to the neutron separation threshold.

See general predictions of the ground state binding energy and other properties in (1981Se06, 1993Pa14, 1997Ba54, 2004La24, 2004Ne16, 2006Ko02, 2012Yu07) and discussion in (1999Ka67).

XREF T1/2(level)
  0ABCD < 100 keV
% n = 100
  2.32E3   D ≈ 150 keV
  6.02E3?   D  

T1/2(level): LABEL=Γ

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Additional Level Data and Comments:

  0 < 100 keV
% n = 100
ΔM= 37112. keV 25, which implies Sn=-82 keV 33.
E(level): ΔM= 37112. keV 25, which implies Sn=-82 keV 33.
  2.32E3 ≈ 150 keV Decay mode not specified.
  6.02E3   Decay mode not specified.

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