278
12.
ALPHA, BETA AND GAMMA RAYS
=
for thorium C” and 1323 X units for radium B + C, equivalent to
2.65 and 0.93 million electron volts* respectively.
‘
12—9.
Sec0nâary Radiations.—When an alpha particle is
-
‘
ejected from a nuCleus, a readjustment takes place in the nucleus
of the product
atom which results in a gamma radiation.
When
the gamma ray photon leaves the nucleus, it may give up its energy
to an electron in the K, L or other X—ray level of the same atom.
This is known as internal conversion.
Photo-electrons or beta rays
are then ejected from the atom and can be studied with a spectrograph. They produce much sharper lines on the photographie
plate than the electrons from the thin foils described in the pre_
ceding section and have been used extensively to deduce the wave_
lengths of the gamma rays
Which caused their ejection.
_
When the atom from which photo—electrons have.been ejected —
returns
to
its normal state, characteristic x—rays are produced.
‘
These, in turn, may pass
out of the radioactive material or, m0re
_
often, they may eject other photo-electrons from still higher levels ‘
in their,,atom. This process
of auto-ionization is called the Âuger
c°ch and the electrons are referred to as Æuger electrons. The X-rays
may also eject photo-electrons from other atoms. The complete
beta ray line spectrum is, therefore, made up of a Complicated
'
system of photo—electrons. The velocities of the electrons range
'
from 29 to 97 per
cent that of light. The corresponding energies — ‘
may
obtained by the use of equations 2—26 and 2—12 and Hr
*
values may be calculated with equation 12—14.
(See tables 9
_
.
.
10.)
.
,
12—10.
The Absorption of Beta and Gamma Rays—Alpha
_
; rays ionize profusely and are easily absorbed. Gamma rays
“duce-comparatively few ions and are absorbed with
.
Beta rays
are intermediate between the
and
:‘The absorption of these rays by a solid substance, suchas
alum1num,maybe measured by placing an appropriate rad10actlVô
substance1nanelectroscope, as
in gure 1Ç7-—1. bselV6
;‘ therateoffallofthe
various ‘thicknesses of alumlnumand
»
produce' bythe
12.
ALPHA, BETA AND GAMMA RAYS
=
for thorium C” and 1323 X units for radium B + C, equivalent to
2.65 and 0.93 million electron volts* respectively.
‘
12—9.
Sec0nâary Radiations.—When an alpha particle is
-
‘
ejected from a nuCleus, a readjustment takes place in the nucleus
of the product
atom which results in a gamma radiation.
When
the gamma ray photon leaves the nucleus, it may give up its energy
to an electron in the K, L or other X—ray level of the same atom.
This is known as internal conversion.
Photo-electrons or beta rays
are then ejected from the atom and can be studied with a spectrograph. They produce much sharper lines on the photographie
plate than the electrons from the thin foils described in the pre_
ceding section and have been used extensively to deduce the wave_
lengths of the gamma rays
Which caused their ejection.
_
When the atom from which photo—electrons have.been ejected —
returns
to
its normal state, characteristic x—rays are produced.
‘
These, in turn, may pass
out of the radioactive material or, m0re
_
often, they may eject other photo-electrons from still higher levels ‘
in their,,atom. This process
of auto-ionization is called the Âuger
c°ch and the electrons are referred to as Æuger electrons. The X-rays
may also eject photo-electrons from other atoms. The complete
beta ray line spectrum is, therefore, made up of a Complicated
'
system of photo—electrons. The velocities of the electrons range
'
from 29 to 97 per
cent that of light. The corresponding energies — ‘
may
obtained by the use of equations 2—26 and 2—12 and Hr
*
values may be calculated with equation 12—14.
(See tables 9
_
.
.
10.)
.
,
12—10.
The Absorption of Beta and Gamma Rays—Alpha
_
; rays ionize profusely and are easily absorbed. Gamma rays
“duce-comparatively few ions and are absorbed with
.
Beta rays
are intermediate between the
and
:‘The absorption of these rays by a solid substance, suchas
alum1num,maybe measured by placing an appropriate rad10actlVô
substance1nanelectroscope, as
in gure 1Ç7-—1. bselV6
;‘ therateoffallofthe
various ‘thicknesses of alumlnumand
»
produce' bythe