55Physical Basis of Nuclear Forensic Science
As Figure 2.11 shows, the Q-value for β
−
decay from
234m
Pa is quite large (2277 keV).
A
s
a
c
onsequence,
β
d
ecay
c
ompetes
s
uccessfully
w
ith
d
ecay
p
rocesses
i
nternal
t
o
234
Pa (referred to collectively as isomeric transition, or IT).
234m
Pa decays with a
h
alf-life
o
f
1
.17min,
9
9.87%
o
f
t
he
t
ime
t
hrough
β
−
decay to low-J states in
234
U, and
0
.13%
o
f
t
he
t
ime
b
y
I
T
t
o
t
he
J
π
= 4
+
234
Pa ground state (sometimes written as
234g
Pa).
234g
Pa, in turn, decays with a half-life of 6.75h to completely different states in
234
U.
T
he
γ
t
ransition
f
rom
234m
Pa to
234g
Pa is so highly converted that no 80-keV photons
a
re observed, and the decay occurs by 100% IC.
Anticipating
o
ur
i
mpending
t
reatment
o
f
n
uclear