NUCLEONICS DATA SHEET No. 1] 
Slow-Neutron Capture Radioisotopes 
Arranged by Half-Life 
By R. C. GEIGER and R. C. PLUMB 
Aluminum Company of America 
New Kensington, Pa. 
The accompanying table lists, in 
order of increasing half-life, the iso- 
topes which are known to be produced 
by slow-neutron capture, excluding 
transmutation reactions. The _half- 
lives of other isotopes of the same ele- 
ment that can be similarly produced 
by neutron irradiation are listed in 
parentheses after each entry. The 
table is useful in the identification of 
isotopes as, for example, for qualitative 
ty, Isotope | 
0.03 sec BY | 
0.85 Li8 
2.5 Er!7! (9.4 d, 7.5 h) 
7.4 N's | 
1 F2 | 
13 In" (49 d, 54.1 m, | 
72 s) 
18 Se7? (123 d, 57 m, | 
17 m, 67 s, 25 m) l 
20 Se*® (85 d) 
24.2 Ag" (2.3 m, 270d) | 
29 o. | 
40 Ne?s 
44 Rh! (4.5 m) | 
57 Ge’? (11.3 d, 82 m, | 
12 h) 
67 Se®? (123 d, 18s, 57 m, | 
17 m, 25 m) | 
72 In (49 d, 54.1 m, 
13 s) | 
1.3 min Sb! (2.8 d, 21 m, | 
60 d) 
3 Dy? (2.32 h) | 
1.4 Ir! (74 d, 19.0 h) | 
2.2 Zn” (250 d, 13.8 h, | 
52 m) 
2.27 Als | 
2.3min Ag!8 (270d, 24.2s) | 
214 
detection of trace-level impurities in a 
neutron-irradiated sample. 
In practice, all of the isotopes of a 
given element will not be observed 
after neutron irradiation. One must 
consider the neutron energies involved, 
the cross sections for the particular re- 
actions, the irradiation and decay 
times, and the relative efficiencies of 
the particular detection system for the 
various radiations and arrive at some 
Isotope Characteristics 
estimate as to which isotopes will 
be detected under a given set of 
conditions. 
To identify an unknown isotope 
completely, the usual procedures of 
characterizing the energy of the radia- 
tion and the chemistry of the element 
by carrier techniques are desirable. 
This table has been compiled from 
data in BNL-325, Neutron cross sec- 
tions (July 1, 1955). 
ts Isotope | ts Isotope 
3.6 min Cr** (27.8 d) | 23.3 min Th? 
3.6 ° Gd" (230d, 18.0h) | 23.5 U2 (2.4 X 10° y, 7.1 
3.76 vee X 10° y) 
3.9 Xe” (5.3d,9.13h) | 24 Sm'*5 (400 d, 47 h) 
42 T12°6 (2.7 y) | 25 Se® (123 d, 18s, 57 m, 
Ls Rh! (44 s) ie til) 
£0 37 (87 d) | 25 Te!*! (110 d, 58 d, 
110 d, 9.3 h, 33 d, 
5.14 Cus (12.8 h) | 72 m, 30 h) 
5.5 Hg?* (47 d) 25.0 [18 
5.8 Te? : 31 Pt! (4.3 d, 18 h) 
6.6 De 37.5 Cl*8 (3.08 x 10° y) 
a 5 ae d48d) | 49 Sn23 (112 d, 14.5 d, 
g 250 d, 27.5 h, 130 
10 Sn! (112 d, 14.5 d, | d, 10 m, 10 d, 
250 d, 27.5, 40 m, | >400 d) 
130 d, 10d, 49 Cd (6.7 h, 5.1 y, 
> 400 d) | 43 d, 53 h, 2.9 h) 
ae ne 4 ane | 52 Zn* (250 d, 13.8 h, 
: Ce) 9h, 2. 2.2 m) 
16.4 Ta'® (111 d) | 54.1 In" (49 d, 72 s, 13 s) 
ly Eee d, 18s, 57 m, | 57 Se®! (123 d, 18s,17m 
67 s, 25 m) 67s,25m) 
18 GD) | Te (110 d, 58 d, 
18 Br® (46h, 35.9h) | 110 d, 9.3 h, 33 d, 
20.2 Ga’ (14.2 h) 30 h, 25 m) 
21 Sb (2.8 d, 1.3 m, | 77 Kr*7 a y, 44 h, 
60 d) l 34.5 
22min Pd (13.6h,17.0d) , 82min  Ge?(11.3d,57s, 12h) 
