2—10.
—sæcrnoscogrcïDETERMINATIONS OF e/m 35:
where B is the angle of
of the electron beam from the
axis of the tube. ' His method, therefore, requires the additional
measurement of the angle 6. Wolf 14has-used the Busch method
_
and found e/m = 1.769 X 107
slightly higher
than the accepted value.
'
'
2—10.
Spectroscopie Determinations of e/m.—When a strong
magnetic eld, H, is placed arou‘nd a source of light it is found that
each spectrum line is split into several lines. In the simplest case,
a
single line Will become two lines equally separated from the
original by the frequency Av. It can be shown that ior this
“
no‘rmal
”
Zeeman pattern,
'
‘
É
,
/
47rAu
-
(2 24)
e
m =_ ——
From simplecases of this type and from more elaborate patterns,
a very precise value of e/m has been determined;
15 namely,
‘
‘ _
'
‘
‘
e/m ; 1.758 ><
_'
"
‘
Precise measurements of the Wave—lengths of
.
'
lines in the emission spectra of hydrogen and ionized helium, and
also of hydrogen and its isOtope, deuterium, have permitted the
Calculation of a value of e/2 of great ac‘curacy.16 Thus
_
:
Î
=
=1.7579 >< 107 e.m.u./g.
‘.
‘
_.
2—11. The MaSs of the Electron—41h the thermionic or" shot7‘effectinethdd
mt:asuringthe charges emit—ted bya hot lament,
'
f
mentioned in chapter and;disçussedinchapter5, itise3tablished
;,
electr0ns_…of
X10—10esu
,
=
expâlmentsabovehaveshown that e/m=
><107 ae,—m-u‘-/&
'
Itfollowsthatthêmass oftheelectron13
<
tr1€ltyassomateWlthM1gramsefthes‘1b3tanœIfth1$ele°‘
.
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