262
12.
ALPHA, BETA AND GAl\/ÏMA RAYS
any gas
in B into the capillary tube at the top. Then a discharge
can be passed through the capillary, which on examination with a
spectroscope
shows the complete helium spectrum.
D
Thus when an alpha particle has slowed down it
picks up
two
electrons and becomes an atom of
helium.
That the helium collected in B is not
due to a trace of this gas
in the emanation is
shown by lling  with pure helium.
Although
A
B
left for a long time, no trace is found to leak
through the thin walls into B.
:
By a method similar to that used in determin—
Î
,
ing the charge to mass ratio of cathode rays, i.e.,
l
by magnetic and electric deflectiom Ea'Ma for
alpha particles has been found to be 4823 e.m.u.
1
per
gram
while
their
velocities
vary
between
p…, 12_2_
The
1.37 >< 109 and 2.06 >< 109 cm. per second.
There
alpha Pê“'tiCl€ is is a characteristic velocity for each of the radio—
thË Îudeus
Of &
active substances as shown in Table 4.
We shall
€ lum atom.
return to a discussion of their velocities in the next
section.
The energy of an alpha particle is of the order of 10“6
ergs or 106 electron volts.
Now, for the alpha particle
Eu
26
=
=
4823 e.m.u./g.
(12—1)
whereas for the hydrogen ion we have (2/le = 9574.
It follows
that the mars of the alpha particle is
Ma = 3.970 AÎH = 6.6 X 1()“24 grams.
(12—2)
The ratio of the atomic weights of helium and hydrogen is also
equal to 3.970.
12—2.
Alpha Ray Spectra.
Nuclear Levels.——It has just been
stated that the alpha particles from a given radioactive substance
all have the same velocity. This is so nearly true that it was not
until 1930 that Rosenblum1 was able to detect and measure a
number of velocities grouped very closely around the previously
known value.
He used the magnet constructed as a memorial to
Pasteur and located at Bellevue, France; which has pole pieces
75
centimeters in diameter and is able to produce a uniform eld of
23,200 gausses over a diameter of 35 centimeters when the gap
is
12.
ALPHA, BETA AND GAl\/ÏMA RAYS
any gas
in B into the capillary tube at the top. Then a discharge
can be passed through the capillary, which on examination with a
spectroscope
shows the complete helium spectrum.
D
Thus when an alpha particle has slowed down it
picks up
two
electrons and becomes an atom of
helium.
That the helium collected in B is not
due to a trace of this gas
in the emanation is
shown by lling  with pure helium.
Although
A
B
left for a long time, no trace is found to leak
through the thin walls into B.
:
By a method similar to that used in determin—
Î
,
ing the charge to mass ratio of cathode rays, i.e.,
l
by magnetic and electric deflectiom Ea'Ma for
alpha particles has been found to be 4823 e.m.u.
1
per
gram
while
their
velocities
vary
between
p…, 12_2_
The
1.37 >< 109 and 2.06 >< 109 cm. per second.
There
alpha Pê“'tiCl€ is is a characteristic velocity for each of the radio—
thË Îudeus
Of &
active substances as shown in Table 4.
We shall
€ lum atom.
return to a discussion of their velocities in the next
section.
The energy of an alpha particle is of the order of 10“6
ergs or 106 electron volts.
Now, for the alpha particle
Eu
26
=
=
4823 e.m.u./g.
(12—1)
whereas for the hydrogen ion we have (2/le = 9574.
It follows
that the mars of the alpha particle is
Ma = 3.970 AÎH = 6.6 X 1()“24 grams.
(12—2)
The ratio of the atomic weights of helium and hydrogen is also
equal to 3.970.
12—2.
Alpha Ray Spectra.
Nuclear Levels.——It has just been
stated that the alpha particles from a given radioactive substance
all have the same velocity. This is so nearly true that it was not
until 1930 that Rosenblum1 was able to detect and measure a
number of velocities grouped very closely around the previously
known value.
He used the magnet constructed as a memorial to
Pasteur and located at Bellevue, France; which has pole pieces
75
centimeters in diameter and is able to produce a uniform eld of
23,200 gausses over a diameter of 35 centimeters when the gap
is