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m= magnetic spectrometer or._spectroggaph around: the mass ‘numberindicate that the mass
studies of secondary electrons, 242+... -assignment is uncertain.
Spect. conv. = magnetic spectrometer or spectrograph
_ty Genetic relationships of thefission productsare
.
studies of conversion electrons, «.7’;Abs.Pb
= absorption of radiations in lead . (when . shown by arrows.A broken arrow indicates the
. elements other than lead were
they relationship has not. been definitely established.
Spect.. ,
iy
designated by their chemical sym-
Parentheses around the half-life of a nucleus mean
Abs.Al conv, =
= absorption in aluminum of conversion 7 _the nucleus is probably formed in fission but has
Mot yet been indentified as a fission product.
. The fission yield values listed opposite the mass
electron coincidences, tot
numbers were generally determined for nuclei apOnly the first three methods listed above have pearinglate in the fission product chain. Ina few
been used extensively for the determination of cases, however, the values apply to isomers in an
gamma ray energies. Of these, spectrometric excited state or to nuclei that can only be formed
determinations are considered to be more reliable directly in fission and not by beta decay.
electrons,
Abs.Al, coine. = absorption in aluminum of secondary ;
than absorption measurements,
Column nine contains three related items, a‘list
these cases, the fission
of the nuclear reactions by which the nucleus has
been produced, its genetic relationships, and its .
mass assignment.
The nuclear reactions are given in the conven-
yield value is only a trae
‘tion of the chain yield (G147).
Description of Figure 1, Yield-Mass Curve
In Fig. 1 (p. 2437) there is plotted on logarith-
mic scale the total yields of the fission product
tional manner with target element listed first,
followed by the projectile and ejected particle in
parentheses.. Conventional symbols are used for
chains, formed in U™* fission, as a function of their
mass nttmbers on linear scale. Forty-two chains
The genetic relationships are included in the
item designated as fission, ‘‘fiss.,”” and only references which contribute to the establishment of
light group at a plane of symmetry between the
nuclei not directly observed.
when its mass number is certain, and a square
when its mass numberis uncertain. The smooth
line drawn through the points corresponds to a
total area of 197% which agrees very well with
the various particles.
are shown in the figure.? The curve was drawn
first with the heavy group reflected upon the
two groups. This was done to permit the averaging of the experimental data of both the light
the relationship are cited.
The abbrevi ation . and heavy groups. The curve was then unfolded
“prec.” signifies precursor of, ‘‘desc.” signifies de- to its present form for greater graphicalclarity.
scendant of, and ‘‘hyp.” signifies hypothetical for A circle is used for the fission yield of a nucleus
In most cases the mass assignment follows di-
rectly from the reactions by which the nucleus
was produced and,for a limited number of nuclei,
by direct measurement with the mass spectrograph, designated ‘mass spect.” In a few instances the fission yield of a nucleus was used as
an index of its mass number, on the assumption
that the fission yield is a smooth function of mass
number (see Figure 1). This methodis adaptable
only in regions of the mass spectrum where the
fission yield is changing rapidly with the mass
number.
Mass assignments made on this basis
are designated as “‘fiss. yld.” The term “ener.”
designates cases in which semi-quantitative use of
the Bohr-Wheeler equation for decay energy
(B10) has been made in arriving at the probable
mass-assignment,
Column ten entitled ‘Other references’ lists
general references and those of lesser significance
which may be useful to an investigator making a
closer study.
Description of Table II, Chains and Yields
In Table II (pp. 2438-41) there is presented a
graphic summary of the chain relations of the fission products, their mass assignments, and fission
yields, The fission product chains are divided
into a light group anda heavy group, The former
contains fission products with mass numbers of
117 or less, and the latter contains those with
mass numbérs greater than 117, Parentheses
the possible 200% resulting from two large fragments perfission.
Description of the List of References
A list of the references is given on pp. 2414-15,
2436, and 2441-42, References are segregated
alphabetically by the initial of the last name of
the first atrthor, A number below 100 signifies
that the reference is to open scientific literature.
A number above 100 signifies that the reference
is to a Project report or other Project publication.
Some of these, such as the well-known Smyth Re-
port (S150), have already been declassified and
given. open printing;
many others are in the
rocess of being declassified and will eventually
be available through the Office of Technical
Services, Department of Commerce, Washington,
D. C., when listed in its weekly Bibliography of
Scientific and Industrial Reports. Many of the
references are to papers written for the collected
Produ volume,
tochemistry and the Fission
roducts, PPR Vol. 9B, the manuscript of which
is not at present available but is in the process of
being edited and declassified for open publication
in the spring of 1947. The volumes of the Manhattan Project Technical Series will be well ad(2) Ed. Note: Grummlttand Wilkinson of the National Research
Council of Canada have recently published a similar yield-masa
curve for about 20 chains (Noiare, 168, 163 (Aug, 3, 1946)),