Table Of ContentOTHER TITLES IN THE INTERNATIONAL SERIES OF
MONOGRAPHS ON NUCLEAR ENERGY
DIVISION I. ECONOMICS AND LAW
Vol. 1—Atomic Power: An Appraisal—C. ALLARDICE (Ed.)
DIVISION II. NUCLEAR PHYSICS
Vol. 1—Neutron Cross Sections—D. J. HUGHES.
Vol. 2—Physics of Nuclear Fission—J. E. S. BRADLEY (Trans.).
Vol. 3—Soviet Reviews of Nuclear Science—Translation of "Atomnaya
Energiya", vol. 3, No. 11 (1957).
Vol. 4—Fast Reactor Cross Sections—S. YIFTAH, D. OKRENT and
P. A. MOLDAUER.
Vol. 5—The Relation Between the Photo-production and the Scattering of
π-mesons—N. F. NELIPA.
Vol. 6—Isobaric Nuclei with the Mass Number A=74—B. S. DZHELEPOV.
Vol. 7—Single Beta-transitions (in translation)—L. N. ZYEYANOVA.
Vol. 8—Systematics of Beta-decay Energies—B. S. DZHELEPOV and G. F.
DRANITSYNA.
Vol. 9—Isobaric Nuclei with the Mass Number /4 = 110—B. S. DZHELEPOV
and N. N. ZHUKOVSKII.
Vol. 10—Isobaric Nuclei with the Mass Number A — 140—B. S. DZHELEPOV,
V. P. PRIKHODTSEVA and Yu. V. KHOL'NOV.
Vol. 11—Isobaric Nuclei with the Mass Number A=73—YE. P. GRIGOR'EV.
DIVISION IV. ISOTOPES AND RADIATION
Vol. 1—Atlas of Gamma-ray Spectra from Radiative Capture of Thermal
Neutrons—L. V. GROSHEV, V. N. LUTSENKO, A. M. DEMIDOV and V. I.
PELEKHOV.
DIVISION V. HEALTH PHYSICS
Vol. 1—Health Physics Instrumentation—J. S. HANDLOSER.
Vol. 2—Radioactive Wastes: Treatment and Disposal—C. B. AMPHLETT.
DIVISION VI. MEDICINE
Vol. 1—Radioisotope Studies of Fatty Acid Metabolism—J. F. MEAD and
D. R. HOWTON.
DIVISION VII. REACTOR ENGINEERING
Vol. 1—Shielding Materials for Nuclear Reactors—A. N. KOMAROVSKH.
DIVISION X. REACTOR DESIGN PHYSICS
Vol. 1—An Introduction to Reactor Physics—D. J. LITTLER and J. F. RAFFLE.
Vol. 2—Radiation Shielding—B. T. PRICE, C. C. HORTON and K. T. SPINNEY.
Vol. 3—Thermal Reactor Theory—A. D. GALANIN.
Vol. 4—Resonance Absorption in Nuclear Reactors—L. DRESNER.
DIVISION XIV. PLASMA PHYSICS AND THERMONUCLEAR
RESEARCH
Vol. 1—An Introduction to Thermonuclear Research—A. SIMON.
ISOBARIC NUCLEI
WITH THE MASS NUMBER
A-74
By
B. S. DZHELEPOV
Radium Institute,
Academy of Sciences of the U.S.S.R.
Translated from the Russian by
PRASENJIT BASU
Translation Editor
REGINALD W. CLARKE
A.E.R.E., Harwell
PERGAMON PRESS
OXFORD LONDON NEW YORK · PARIS
1963
PERGAMON PRESS LTD.
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A translation of the original volume
Izobarnyye Yadra s Massovym Chislom A = 74
(Izdatefstvo Akademii Nauk SSSR)
M oscow- J 960- Len i ngrad
Library of Congress Card Number: 61-11524
Printed in Great Britain hy the Pitman Press, Bath
4 = 74
1. Introduction
Five known isotopes - ^Ga, ^Ge, 74^ 74g
Sf e
and ^Br - have the mass number 74. Of these ^Ge
and are stable.
Fig. 1 illustrates the transitions between isobars
with A = 74. As is well known, two parabolas, corres-
ponding to even and odd Z, are obtained on plotting
the relation between the mass of the isobars and the
atomic number. These parabolas can be calculated
with the help of Levy's empirical formulae· For
A = 74 the situation is complicated by the fact that the
Fig. 1
Distribution of nuclei with A = 74 on isobaric parabolas
1
2 ISOBARIC NUCLEI WITH MASS NUMBER A = 74
A=*74 nuclei belong to two neighbouring groups Λ <J 40 and
N > 40, differing in nuclear structure and, corres-
pondingly, in their Levy coefficients.
Levy's parabolas are drawn with dotted lines on
Fig. 1. The mass differences of ^Αβ - ^Ge and
are known experimentally. The points
denoting the nuclei of 74As and ?4Se are plotted froxn
experimental data and do not fall exactly on the para-
bolas. The remaining points are calculated·
"Ga
7.5 min; ß~, γ
2. Data on Decay
74Ga was discovered by Morinaga in 1956 [1]. It
has a half-life of 7.5 ± 0.4 min according to [2], 8
min according to [1], and 7.5 ± 0.5 min according to
[4].
Morinaga obtained ^Ga irradiating natural
on
germanium with neutrons. Eichler and others [2],
and then Grits and others [4], found that an activity
with a half-life of about 8 min appears only when 74Ge
is irradiated with neutrons (the authors of both these
Capers used 7*Ge of 97 per cent purity)· The reaction
4Ge (Λ, p) 7^Ga proceeds with neutrons from Be + d
(10 MeV) [1] and T + d [2]· The empirical formulae
for nuclear masses, predict a large mass difference
for 74ca - 74Ge (5.09 MeV according to Levy [5, 6]
and 5.82 MeV according to Cameron [8]. Hence it is
clear that neutrons with an energy greater than 5 MeV
are necessary for obtaining ^Ga from the (/i, p) re-
action. The cros s-section for the reaction for T - d
neutrons is 25 ± 10 millibarns [4]·
Morinaga [1] noted 3 γ-line s whose intensity de-
creased with a period of 8 min : /tv = 580, 2300 and
2600 keV. Eichler and others [2] found an intense
line of 600 KeV and less intense lines Av = 860, 1900,
2300 keV, and weak lines with /» = 1100 and 1500 KeV.
The first line is undoubtedly associated with the first
level of excitation of 74Ge, E\ =596.3 KeV, which is
well known from the ß-decay of ^As, from the
coulomb excitation of 74Ge and from the resonance
scattering of γ-rays of 74As (see 74Ge).
The second level of 74Ge has, apparently, an
3
4 ISOBARIC NUCLEI WITH MASS NUMBER A = 74
Î4G* energy of — 1200 KeV. It is possible that the weak
line of 1100 keV, observed by Eichler and others [2],
is due to the discharge of this level.
The third level of 7^Ge, judging from the γ- spec-
trum of 74As, has an energy of 2230 + 70 KeV. It is
possible that the line ÄV = 2300 KeV, observed by
Morinaga [1] as well as Eichler and others [2], is
associated with the direct discharge of this level of
74 e.
G
The arrangement of the other levels of ?4ç is
e
unknown. In 1956 Morinaga [3] systematized the data
on the distribution of the first odd levels in the even-
even nuclei and found the relation E ~ 67 A'^A MeV,
which gives about 2.7 MeV for A = 74. 74Q probably
a
has an odd ground state (the 31st proton is at the odd
level p\ and the 43rd neutron at the even level g\).
This explains the large probability of decay to the
upper odd levels of 7*Ge (as occurs in ^Ga).
The mass difference of 74Ga - ?4Ge according to
the ß-systematization of Levy [5] and Riddell [6] is
5.09 MeV. If the decay had occurred between ground
states, with this mass difference and a period of 7.5
min we would get τ/ = 5.3 x 10° (log τ/ = 6.72). This
value of the product if shows that no allowed transi-
tion of ^Ga to the ground state of '4Ge takes place.
This is in agreement with the supposition stated above
rTehgea rcdhianrga cthtee rdisitfficesr en0+t apnadr it1i esc aonf b?e4G rau laend(j o7u4tQ Ôf# or
74 a.
G
It is pointed out in paper [2] that the γ-line /ivjz^
600 keV is considerably more intense than the others
during the decay of ^Ga. This compels one to con-
clude that a considerable portion of the disintegrations
of 74Ga occur at the level 596.3 keV of 74Ge. Conse-
quently, for these disintegrations log τ/ exceeds 6.7,
but not greatly. It may therefore be inferred that
β-decay at this level is apparently a first forbidden
transition and hence the ground state of is odd
with a spin not greater than 4. We may point out that
the same spin can be expected in ?^Ga according to
the theory of shells, since the 41st and 43rd neutrons
are situated at the same level. The experimental
value of the spin of 72Ga is 3 [7]. This makes probable
ISOBARIC NUCLEI WITH MASS NUMBER A = 74 5
7*Ca the supposition that the ground state of ''Ga is 3".
(In all odd-even isotopes of Ga and As, except ^As,
the spin is equal to the difference of the moments of
the odd proton and neutron; for ^Ga d
an
74Ga this
gives 3").
74
Ga
Z5T '(31
860
\1500\
1 y wool
2220
1200 2"
596.3 Z+
? ?
0 0+
74-, Ge
Fi8· 2 7X
Decay scheme of '^Ga
The proposed decay scheme of '^Ga is given in
Fig. 2. It should be noted that ^Ga does not,
apparently, have long-lived isomers, otherwise they
would have been observed in specially staged experi-
ments [9] on the reaction 7^Ge (</, a) 74Ga.
6 ISOBARIC NUCLEI WITH MASS NUMBER A = 74
74Ga Bibliography on ^Ga
Properties of ^Ga
H. MORINAGA, Phys. Rev. 103, 504 (1956).
[;i
E. EICHLER, N. JOHNSON, G. O'KELLEY,
Bull. Am. Phys. Soc. j>, 62 (1958).
3] H. MORINAGA, Phys. Rev. 103, 503 (1956).
4] Yu. GRITS, I. SELINOV, D. KHULELIDZE,
Ye. BARONI, V. GUSEV, V. ZOLOTAREV,
Atomnaya energiya No. 12 (1958).
Other Works
[5] He LEVY, Phys. Rev. 106, 1265 (1957).
[6] J. RIDDELL, A table of Levy 1 s empirical atomic
masses. GRP-654, AECL No. 339 (1957).
[7] L. GOODMAN, W. CHILDS, Bull. Am. Phys.
Soc. 3, 21 (1958).
[8] A. CAMERON, A revised semi-empirical atomic
mass formula, AECL No. 433 (1957).
[9] D. McCOWN, L. WOODWARD, M. POOL, Phys.
Rev. 74, 1311 (1948).
*Ge
stable; 36.5 per cent
74Ge is a stable isotope of germanium. Its rela-
tive abundance according to the two latest papers is
36.74 per cent [1] and 36.35 + 0.04 per cent [2]
(weighted mean)·
3. Properties of the Ground State of 74Ge
Since '^Ge has an even number of protons and
neutrons, the empirical rule predicts that its ground
state is of the type 0+. This was verified as regards
the magnitude of the spin by Townee and his colleagues
[3] by the micro-wave method.
The electrical quadrupole moment of 74Ge is less
than 0.007 x 10~24 cm2 [3].
No direct determinations of the mass of ^Ge have
been made as yet. No measurements have been made
of any mass-spectroscopic doublet of mass 74, or of
Q for reactions connecting ^Ge and 74Se with other
nuclei [22, 23]. There are, it is true, micro-wave
determinations [24] of ratios 74Ge - 72Ge/74Ge - 70Ge
etc., but these do not allow determination of the mass
of 74Qe with sufficient accuracy·
The only method of determining the mass of 74Ge
now available is by means of ^As.
The mass difference 74As - 74Ge = 2532 + 15 keV
is known within 15 keV from the decay scheme of
74Ae. But the absolute value of the mass of 74As is
known only to a far smaller degree of accuracy (see
74As,'p.4-l ), thus
7
