12—4.
RANGE-VELOCITŸ-ENERGŸÆIFE
267
is equal to the range of the alpha particles. The values in table 5
give the minimum thicknesses of material required to stop the particles from radium C’ and from polonium. - Due to the straggling,'
slightly thicker materials must be used in practice to cut off all the
particles.
12—4.
Range-Velocity—Energy—Le Relations.—Tables 4and 7
'
at the end of this book gives values of the mean range R for alpha
.
particles of various initial velocities 00 and energies (Æ, (relativity '
values).
For ranges in standard air,= between three and seven ‘
centimeters, the approximate Geiger law may be used. Thus,
?”
”= avo3 ..‘= àâ%,
(12—4)
where v., is in centimeters,r is the (extrapolated) range in Centi—
.
meters and a = 9.25 >< 10—28.
For the 10wer velocities, the expo'
nent of 00 drops to 1.5 and for the higher velocities it.increases to 4.
An uns-table atom has a short life and sends out long range, high
velocity, high energy alpha particles. If )» is the fractional number of atoms breaking up each second (= 0.693 divided by the
time T for one-half of a given amount of radioactive substance to
change into its next element), then,
.
.
_
'
log
=
 + Blog R,
'
_
(12—5)
Where  and B are constants.
This is known as the Geiger-Nutfal_l
relation and was discoVered empiricallyain 1911. This law has
proved useful .in determining
transformation 'constant >\ of
‘
neWly discovered subSt'an‘c63;
is“fnojt Ôfçhigh accuracy
and a
bad exception oc“curS in
of act1n1umX,
seen in
_
gure 12—7. "À in
for the differèntseries,
’
_
while the slopè of the
a
.
,
probability of a transf0rmation and
_
the energy oftheemittedalphapart1clesuggests ;that
a
’
ofthe nucleuswh1chœheld1nC0mm0bÿ the d1f_°fe'rèth
members ofag1venradmactweserresIn
appliçauonj of
; Gamowhaveshwnthatnlyonef@rm0fthe P0tmt1albamer
’
“
RANGE-VELOCITŸ-ENERGŸÆIFE
267
is equal to the range of the alpha particles. The values in table 5
give the minimum thicknesses of material required to stop the particles from radium C’ and from polonium. - Due to the straggling,'
slightly thicker materials must be used in practice to cut off all the
particles.
12—4.
Range-Velocity—Energy—Le Relations.—Tables 4and 7
'
at the end of this book gives values of the mean range R for alpha
.
particles of various initial velocities 00 and energies (Æ, (relativity '
values).
For ranges in standard air,= between three and seven ‘
centimeters, the approximate Geiger law may be used. Thus,
?”
”= avo3 ..‘= àâ%,
(12—4)
where v., is in centimeters,r is the (extrapolated) range in Centi—
.
meters and a = 9.25 >< 10—28.
For the 10wer velocities, the expo'
nent of 00 drops to 1.5 and for the higher velocities it.increases to 4.
An uns-table atom has a short life and sends out long range, high
velocity, high energy alpha particles. If )» is the fractional number of atoms breaking up each second (= 0.693 divided by the
time T for one-half of a given amount of radioactive substance to
change into its next element), then,
.
.
_
'
log
=
 + Blog R,
'
_
(12—5)
Where  and B are constants.
This is known as the Geiger-Nutfal_l
relation and was discoVered empiricallyain 1911. This law has
proved useful .in determining
transformation 'constant >\ of
‘
neWly discovered subSt'an‘c63;
is“fnojt Ôfçhigh accuracy
and a
bad exception oc“curS in
of act1n1umX,
seen in
_
gure 12—7. "À in
for the differèntseries,
’
_
while the slopè of the
a
.
,
probability of a transf0rmation and
_
the energy oftheemittedalphapart1clesuggests ;that
a
’
ofthe nucleuswh1chœheld1nC0mm0bÿ the d1f_°fe'rèth
members ofag1venradmactweserresIn
appliçauonj of
; Gamowhaveshwnthatnlyonef@rm0fthe P0tmt1albamer
’
“