No abstract

5 cm H QUARTZ N^He ^JJ=<} FLOW -» ; PUMP ^v_ DISCHARGE RESONATOR ESR CAVITY FIG. 2. Diagram of gas-flow system.signals were obtained when the partial pressures measured 25 cm downstream from the ESR cavity were 0 J3 Torr of nitrogen and 3.2 Torr of helium. No signals could be observed in pure nitrogen afterglows«The g factors were determined from the central line of each of the spectra to be 0 e 8002 ±0.0004 for the 2 D 3/2 level and 1.2005 ±0.006 for the 2 D 5/2 level, in agreement with the theoretical Land£ g factors | and 6/5. Each of the spectra exhibits three groups of lines, due to the magnetic hyper fine splitting caused by nitrogen's nuclear spin of one. The measured separations of the three groups are 58o5 G for the 2 JD s/2 spectrum and 68 G for the 2 Z) 5/2 spectrum. Theoretical separations, based on the central-field approximation 2 and accurate analytical wave functions, 3 are calculated to be 69 G for both spectra, in fair agreement with the measured values. The splittings within the three hyperfine-structure groups of each spectrum result from the second-order Zeeman interactions between the two fine-structure levels. The measured splittings agree within 10% with those calculated from second-order perturbation theory, 2 using the known level separation of 8 cm™ 1 . A more detailed analysis of the spectra, including the effects of electric-quadrupole hyperfine structure, deviations from LS coupling, configuration interaction, and relativistic corrections, will be published elsewhere.Measurements of the 4 S ground state concentration showed that approximately 5% of the nitrogen atoms were in the 2 D levels. The relative intensities of the 2 D 3/2 and 2 D 5/2 spectra showed these levels to be approximately in thermal equilibrium.Further experiments are under way to measure the spectra more accurately, to measure the linewidth as a function of pressure, and to look for other metastable levels (a preliminary scan did not reveal the presence of the 2 P levels of nitrogen).

Phys. Rev. Letters 15, 917 (1965)].