We have observed the decay of one atom of the doubly even isotope 108. We observed
-decay with a halflife, of (76
–36
+364
)
s. The full
-decay energy could not be measured, as the
escaped the detector. With the knowledge of the halflife, an estimate on the
-decay energy can be made.
From the formula of Rasmussen
9 and a reduced
-width of 1, a value which has been measured for
260106 and also for the doubly even isotones of N=156, we obtain Q=(11.0
–0.3
+0.1
MeV. This value is higher than given by Moeller
10 (10.35 MeV), and agrees with that of Uran and Zeldes
11 (10.9 MeV). A hindrance factor w
of 0.5 increases the Q
-value by 0.14 MeV. The mass excess of
264108 follows as (120.0±0.3) MeV. The groundstate shell effect amounts to (–5.0±0.3) MeV using the macroscopic mass values of Ref. 10. The formation cross section of (3.2
–2.6
+6.1
) pb overlaps with the value of
5 pb from Dubna for the 6 ms sf-activity mentioned initially but is considerably lower than an extrapolation from the reaction
58Fe (
208Pb,n)
265108 which gave 10 pb with the lower limit of 4 pb.