DIELECTRIC CONSTANT, ABSORPTION AND SCATTERING 301 
Taste 21. Temperature variation of the dielectric 
properties of water.53,39 ) = 0.50 cm.” 
°C n k €r 4 o@ mhos/m 
0 $18 «76 «| 701 12 87.8, 
5 3.50 2.03 8.13 14.2 47.3 
10 3.80 2.25 9.38 17.1 57.0 
15 4.10 2.41 11.0 19.7 65.6 
20 4.39 2.54 12.8 22.3 74.3 
25 4.67 2.62 14.9 24.4 81.3 
30 4.94 2.67 17.3 26.4 88.0 
35 6.21 2.69 19.9 28.0 93.3 
40 5.47 2.69 22.7 29.4 98.0 
Tasix 22. Temperature variation of n, k, ¢, ¢; and o.38,39 
A = 3.2 cm. 
t°C n k & & o mhos/m 
0 7.10 2.89 42.0 41.1 21.4 
5 7.63 2,62 51.3 40.0 20.8 
10 8.00 2.33 58.6 37.3 19.4 
15 8.22 2.00 63.6 32.9 17.1 
20 8.33 1.72 66.4 28.7 14.9 
25 8.38 1.50 68.0 25.1 13.1 
30 8.39 1.31 68.7 22.0 11.4 
35 8.38 1.16 68.9 19.4 10.1 
40 8.35 1.02 68.7 17.0 8.85 
constants of ice were made in the centimeter wave- 
length range. The British workers*’ used the resonator 
Q method at 3 and 9 cm. The latest results on both 
these wavelengths are collected on the accompanying 
graph (Figure 26). The temperature range extends 
from about —50 C to 0 C. The refractive index turns 
out to be constant in this range. It was found to be 
equal to 1.75 at 3.01 cm and 1.72 at 9.18 em. The 
absorption index increased in this temperature range 
from about 0.0001 to 0.0010. 
CS Le 
mo xe 
OZ NIT 
mc ON Tt 
Jat a a 
_ edema 
qQ Q2 03 04 30 4050 7003 ® 
Ane 
P= 
Para 28 
26 
24 
80 
70 
"60 
Ficurs 25. Refraction and absorption indices for 
water. 
Younker,” using the standing wave ratio method 
at 1.25 cm, found at about —15 C 
e, = 3.3 and « = 0.011, or c = 0.013 mhos/m. 
These data can be compared with those obtained at 
3.01 cm,*7 where 
er = 3.06 and ¢; = 0.00080, c = 0.00044 mhos/m. 
The difference at these two wavelengths between the 
conductivities appears much too large and further 
studies should clear up this discrepancy. The dielectric 
losses in ice in the centimeter region are, however, 
very small. 
IL SACQES OBTAINED AT 3,01 CM ON 
TWO DIFFERENT SAMPLES 
© VALUES OBTAINED AT 9.18 CM 
45 -40 -35 -30 -25 -20 45 105) 7-5 ° 
TEMPERATURE IN DEGREES CG 
Ficure 26. Absorption index (kx10+8) versus tem- 
perature for ice. 
At much lower frequencies the dielectric behavior 
of ice is given in Figure 27%. These data refer to a 
temperature of —12 C.*7 
ATTENUATION DuE TO WaTER VAPOR 
In order to determine the attenuation due to water 
vapor, Saxton endeavored to measure the refractive 
and absorption indices of water vapor.*® Using the 
resonator Q method, he found that by passing from 
9 to 3.2 em the real part of the dielectric constant 
changes from 1.0056 to 1.0051. According to a general 
relationship connecting the real and imaginary parts 
of the complex dielectric constant,*® the indicated 
variation of (e,—1) given by Saxton should be accom- 
panied by a tremendous absorption by water vapor in 
the microwave region as pointed out by Van Vleck.*® 
This is contrary to the data available and rules out 
the frequency variation of (e-—1) given by Saxton. 
cloth oS Oe! Nilo NIO7 Gulo= Mom a 
FREQUENGY IN C 
Ficure 27. Loss factor and dielectric constant of ice. 
