Lifetimes of Levels inA=10Nuclei

Abstract

The Doppler-shift attenuation method was used to obtain the following mean lifetimes (in psec) for the indicated nuclear levels: 10 C(3.36), r=0.155 ±0.025; 10 B(3.59), r=0.150±0.015; 10 Be(3.37), r=0.189 ±0.020; 10 B (2.15), r= 2.7_ 0 .4 +0 -8 . A limit of r <30 fsec is obtained for 10 B (1.74), which is a factor of 8 greater than, and therefore consistent with, the lifetime computed from the analog 0 decay of 10 C. Transition strengths obtained from the 10 B(2.15) and 10 B(3.59) lifetimes are in good agreement with the effectiveinteraction calculations of Cohen and Kurath, as modified by Warburton et at. The 10 C(3.36) and 10 Be(3.37) states decay by analog E2 transitions: 2 + , r=l-»0 + , T=1, with 7%=±l, whose strengths are well described by calculations of Kurath's for an effective charge €«= € p =0.5. An upper limit was obtained for the corresponding transition 5.17 ->1.74 in 10 B(r*=0) which is consistent (factor of 4 greater) with the analog strengths observed in the T e -ztl nuclei.

Lifetime of the21+state in10C

“…This lifetime is substantially longer than the previous value obtained by Fisher et al, [8]. Figure 4 gives a comparison of the current measurements (solid symbols) and those of Ref.…”

“…To compare the present technique with a normal kinematics DSAM measurement, the original Fisher et al, experiment [8] was also repeated with Gammasphere. This regular-kinematics experiment was performed with a 9.5-MeV proton beam incident on a 10 B target followed by a gold backing.…”

“…A pioneering Doppler Shift Attenuation Method (DSAM) experiment by Fisher et al, [8] in 1968 was aimed at understanding these issues and testing the intermediate-coupling shell model predictions by measuring the decay rates from the first excited states in 10 C and 10 Be. However, the DSAM technique was new and only ∼20% precision could be achieved.…”

Precise Electromagnetic Tests ofAb InitioCalculations of Light Nuclei: States inBe10

“…These states have very different properties and provide a delicate test of both the Hamiltonians and the calculational methods. The Argonne v 18 (AV18) NN [11] interaction predicts a separation of only 0.23 (15) MeV for these states, one with a negative (oblate) intrinsic quadrupole moment and a small B(E2) decay to the ground state, and one with a positive (prolate) quadrupole moment which is much more collective. The oblate state is lower in energy with just AV18.…”

“…From this velocity difference, the lifetime of the level can be determined if the slowing history of the ion is known. Careful selection of the kinematic conditions for producing the states of interest at high velocities where stopping powers are well categorized, control of feeding from higher levels, and advancements in γ-ray detection all are important for moving beyond the original >25% measurements from the 1960s [14,15] and improving both precision and accuracy.Excited states in 10 Be were populated in the 7 Li( 7 Li, α) 10 Be reaction. Beams of 7 Li ions of up to 50 pnA and energies of 8 and 10 MeV were produced by the ATLAS accelerator and impinged on thin 7 Li metal and 7 LiF targets.…”