出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We suggest a 138La - 138Ce - 136Ce system as a new nuclear cosmic clock for measuring the time
elapsed from a single neutrino process episode to the present. This clock is applied to meteoritic
samples produced mainly by a single nucleosynthesis episode. The nuclear structure of 138La
is crucial for the performance of this clock and its astrophysical origin. The lowest 1+ state in
138La has not been established experimentally. If this state is a b unstable isomer, 138La should
be destroyed in the n -process and the clock cannot work well. However, this system can be used
as a new cosmic thermometer. To study the nuclear structure of 138La, we perform a shell model
calculation. Our shell model calculation shows the 1+ state may be stable against the b decay
and our proposed clock can perform.
