PROCEEDINGS 
OF THE 
NATIONAL ACADEMY OF SCIENCES 
Volume 7 NOVEMBER 15, 1921 Number 11 
THE MOBILITIES OF ELECTRONS 
By Leonard B. Loeb* 
Ryerson Physical Laboratory, University of Chicago 
Communicated by R. A. Millikan, Aug. 17, 1921 
In a recent paper 1 it was shown that the electrons could presumably 
travel through N2 and H2 gases in a free state at atmospheric pressure. 
It was found in some cases impossible to evaluate the mobilities of these 
electrons with the low frequencies of commutation available. The val- 
ues of the mobilities indicated by these results appeared to be so much 
higher than the values obtained by earlier investigators that it was felt 
worth while to attempt to measure them accurately. 
The mobilities of electrons were accordingly determined in N2 using 
the high frequency oscillations obtained from two Western Electric Com- 
pany "E" tube oscillators operating in parallel. The diagram of connec- 
tions is shown in figure 1. In some cases the oscillations were taken 
directly from the primary condenser Ci, and at other times from the con- 
denser C2 of a secondary circuit tuned to resonance with the primary 
circuit. The method of measurement was the well known Rutherford 
alternating current method. The electrons used where photo electrons 
liberated by ultraviolet light from one of the plates. The ionization 
chamber used was similar to the one used in measurements of the constant 
of attachment of electrons to gas molecules, 2 except that still greater pre- 
cautions were taken in this chamber to avoid contamination. The meas- 
urements were made in the same manner as were the measurements for the 
determination of the coefficient of attachment. The current to the elec- 
trometer plate was measured as a function of the value of the alternating 
potential between the plates. This current was then plotted against the 
potential difference thus yielding a mobility curve. The potential differ- 
ence Vq, at which this curve cut the axis was substituted in the equation, 
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