14-20.
PHOTO…DISINTEGRATÏON
329
Furthermore, the half—life of a radio-active substance is the
same,
regardless of the method of production. For example,
'
T = 10.5 minutes for 7N13* when produced by deuteron
ment of carbomtwelve or by alpha particles upon boron—ten.
'
Neutrons ma
be
roduced convenientl b
bombardin li ht
_
Y
P
_Y Y
_
g
g
elements W1th deuterons.
For example, 1f energet1c (17 Mev)
neutrons With a wide distribution of velocities are desired,
'
.
gLi7 + 1H2 —> 22He4 + on1.
_
(14—30)
Sharper groups of lesser energy (4.5 Mev) may be obtained from
41369 + 1H2 _) 51310 + 0n1.
(14—31)
A more homogeneous group, but of lesser energy
Mev) may
he had from
‘
'
_
"°'='
'
1H2 + 1H2 —> 2H€3 + 0n1-_
.(14—32)
For comparison With the above, the radon—beryllium source gives
neutrons With a broad energy distribution up
to 12 or 14 MeV. A
_
very homogeneous group
of neutrons may be had by bombardmg »
_
beryllium With gamma rays. In this-case, the energy depends onthat of the incident photons (v),
.
.
_
In order to explain the di3integratmH of heav1er_ elements by
.
means of deutero‘ns,
Phillip&_2_8 assumed
that at
the collision the deutercin
into & proton and a,neutron,_
the latter entering
Th1s
a partzal_çapîure.
_
There is some
asto Whether the
_
of deuterons
possible,
spht .
_
into neutr0ns and
‘
_
14-20.
"
rays ;Ca?
cause
art?“
cial
” of elementS,W1ththe
of charge—d
f ??
::»;
=
_
iH2+r-->1Hl+an1
.
_
'Ï‘Ï[_
;
‘
»
_
_