Ammonia gas is known to exhibit a strong absorption in the region of 0.8 cm" 1 . By sweeping the frequency of a continuous wave oscillator and using a balanced wave guide system with one arm of the wave guide serving as an absorption chamber, thirty lines of the fine structure, as predicted by Sheng, Barker, and Dennison, have been observed in this region. Their intensities and frequencies have been measured for two different temperatures and an empirical expression for the frequencies of the lines in terms of their rotational quantum numbers is given. At pressures of 5 X 10 _1 mm Hg and below T , the lines are very well resolved. At pressures of 10~2 mm Hg and below, a definite hyperfine structure appears. The Stark effect is also observed when a d.c. field is applied to the absorbing gas.

the absorption line due to the transition from the /= 1 to the / = 2 molecular rotational level has been resolved and shown on an oscilloscope. This line appears at the frequency of 24,320 megacycles or 0.8107 (cm -1 ) wave numbers. The line was resolved at pressures of less than 10" 1 mm of Hg. At pressures greater than this, the pressure broadening of the line was so great that the line was hardly observable by the oscilloscope method. The gas was introduced for the measurements, into a rectangular wave guide through which the microwaves were transmitted. Further details concerning the method can be found in the paper cited.Carbon oxy-sulphide, OCS, is a linear molecule with the carbon atom between the oxygen and sulphur. Its moment of inertia calculated from the above frequency is 1.379 X10" 38 g cm 2 .The value (1.38X 10~3 8 g cm 2 ) calculated using the interatomic distances observed by Cross and Brockway, 2 agrees well with this.A linear molecule of this sort should show a Stark effect shift and splitting proportional to the square of the electric field strength and the square of the dipole moment. 3 When a d.c. electric field was applied to the carbon oxy-sulphide in the wave guide with the d.c. field parallel to the direction of the polarized electric vector of the traveling microwave, the rotational line split into two lines. One of these lines moved to a lower frequency than the unperturbed transition line and the other moved to a higher frequency. This effect was instantly (and to the authors, spectacularly) observed on the oscilloscope screen as the d.c. voltage was gradually increased. The single peak observed on the oscilloscope divided into two peaks, one of which was twice as high as the other. Figures 1-3.The line which showed the least shift appeared twice as high (intense) as the other, in agreement with the theory. The energy level for the positive external (spatial) quantum number is the same as for the negative. Therefore, the 2(/-f-l) states become only (7+1) levels. The frequency shift was found to be proportional to the square of the electric field strength, agreeing with the theory. Because the d.c. electric field is in the direction of the electric vector of the traveling microwave, no transition in the external quantum number occurs here when the rotational quantum number changes. Therefore, the frequency separation of the two lines from each other should be:where p is the dipole moment and E the d.c. field strength. From the above equation the observed value of A/ and I, the moment of inertia, the dipole moment can be calculated. It was found to be 0.72 X10~1 8 e.s.u. The principal uncertainty in the measurement is the separation of the THE EDITOR FIG. 1. FIG. 2. FIG. 3.FIGS. 1-3. Oscilloscope pictures of absorption versus frequency for the OCS rotational line at 24,320 megacycles. The applied d.c. volts is 0 volt/cm in Fig. 1, 750 volts/cm in Fig. 2, 1070 volts/cm in Fig. 3. The frequency markers in the oscilloscope pictures are 6 megacycles apart in each case and appear as points of...

The structure of the hyperfine spectrum of N 14 H 3 in the microwave region has been carefully re-examined. It has been found that the N 14 quadrupole line spacings for K ?*1 can be fitted within experimental error to previously developed theory, provided a small change in the quadrupole coupling constant eqQ due to centrifugal distortion of the molecule is allowed for. For K=l) and /=2,3,4, a doubling of each line of the quadrupole pattern has been found which increases from about 70 to 150 kc/sec with increasing /. It has been possible to explain these new features of the spectrum in terms of the interactions of the magnetic moments of the protons with the molecular magnetic field caused by rotation and with the magnetic moment of the N 14 nucleus.

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