l
.
7—5.
IONIZING POTENTËALS
145
of V, (V — 21.12), (V — 22.93), and (V — 23.63) electron volts
and hence the helium atoms absorbed 21.12, 22.93, and. 23.63
electron volts of energy.
The signicant point is this: the atoms
absorbed particular amounts of. energy,
not any- amount, sug—
gesting an inner structure inthe atoms, of nite rather than continuous energy values.
_
_
7—5. ' Ionizing Potentials.6’7—We shall now see some of the
methods used to prove that the electrons in undisturbed atoms
bound to the nucleus by xed forces and require the addition
Of denite amounts of energy to remove them from their normal
…
state to the outside of the atom.
_
Ï
In the discussion of thermionic emission and vacuum tubes,
as presented in chapters 5 and 6,‘it was assumed that there was
'
,]
_Ps
& P.
‘
,
_
.,
-p,
,
.
,
13
,
_
_
>
'
‘A
\
“
;
o
ï
,
‘
'
:
,
,
,
'
_‘
‘
'
.
:-:=:—‘-s—-‘-‘Œ:£e;—£‘ê*
…
0
,
.
…
…
_…l1Jllllllh
L
FÎG. 7—4. The effect. [of gases1na
.for obtaining
two-‘elecrr-‘odef 1» hév“‘gufc H-‘
n° â‘aÏS present mthetubeUndersuchaœndmn the “current—"
.
'
bythelamentbangdrawnovertothePÏateas
l?Y
‘
Inpaftlcular1t18‘themzmmumZWWÆPWWWÏfthedlstanœ