_
12—2.
ALPHA RAY SPECTRA
263”
6 centimeters.
The alpha particles from a given radioactive sub.
were
collimated With slits, ’and,’ after deection through
degrees With the_strong magnetic eld, formed ne lines on a
photographic plate. From the sharpness of the lines in this so_ ‘
called ne structure spectrum, it is seen that among the alpha particles which leave a given substance, all With approximately the
‘
same velocity, there are distinct sub-groups, each containing particles of but one velocity.
’
_
.
Later, Rutherford and his associates 2 used a“ shallow ionization chamber (se‘e chapter 18) to detect the alpha particles,
rather than a photographie plate, thereby making possible…the
study of extremely weak groups. The eldof their “ annular ”
magnet is conned to a narrow ringbf mean diameter 80 centimeters and amounts to approximately 10,000 gausses.
,
It has been found that certain substances such as Rn, RaA and
Po have but one line, While others, such as ThC, An,
and RdAc, have two or m0re lines.
That the velocities of the
particles from any one substance are all of nearly the same velocity
may be seen from the typical case of ThC, where the particles in
one of the lines (ai) have a velocity only 10034 times that of the
average of the group.
The short-lived substances,RaC' and ThC’
,
emit a few
of much higher .velocity, in addition to
the main group of lines. Tables of alpha ray Spectra Will be found
'
in the literature.3_
-
.
.
.
,
In the preceding chapter we have seen that alpha particles are
'
emitted from the nucleus of the atom.f The fact that they are —
'
emitted in denite
(velocity) groups suggests that there
are energy levels in the nuclei _of'these,atoms.
ÏVVhen
alpha
particle is ejected
nucleus, 1t
expected that a
.‘
readjùstréñt
transitions of the alpha
particles
be accompanied
‘
.
by“ the dtfgmmmt lttt in
been foundthattheenerg1es(v)ofthevarwusgammarays
,
'
»
12—2.
ALPHA RAY SPECTRA
263”
6 centimeters.
The alpha particles from a given radioactive sub.
were
collimated With slits, ’and,’ after deection through
degrees With the_strong magnetic eld, formed ne lines on a
photographic plate. From the sharpness of the lines in this so_ ‘
called ne structure spectrum, it is seen that among the alpha particles which leave a given substance, all With approximately the
‘
same velocity, there are distinct sub-groups, each containing particles of but one velocity.
’
_
.
Later, Rutherford and his associates 2 used a“ shallow ionization chamber (se‘e chapter 18) to detect the alpha particles,
rather than a photographie plate, thereby making possible…the
study of extremely weak groups. The eldof their “ annular ”
magnet is conned to a narrow ringbf mean diameter 80 centimeters and amounts to approximately 10,000 gausses.
,
It has been found that certain substances such as Rn, RaA and
Po have but one line, While others, such as ThC, An,
and RdAc, have two or m0re lines.
That the velocities of the
particles from any one substance are all of nearly the same velocity
may be seen from the typical case of ThC, where the particles in
one of the lines (ai) have a velocity only 10034 times that of the
average of the group.
The short-lived substances,RaC' and ThC’
,
emit a few
of much higher .velocity, in addition to
the main group of lines. Tables of alpha ray Spectra Will be found
'
in the literature.3_
-
.
.
.
,
In the preceding chapter we have seen that alpha particles are
'
emitted from the nucleus of the atom.f The fact that they are —
'
emitted in denite
(velocity) groups suggests that there
are energy levels in the nuclei _of'these,atoms.
ÏVVhen
alpha
particle is ejected
nucleus, 1t
expected that a
.‘
readjùstréñt
transitions of the alpha
particles
be accompanied
‘
.
by“ the dtfgmmmt lttt in
been foundthattheenerg1es(v)ofthevarwusgammarays
,
'
»