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The photography and wave-lengths measurements and analysis of the TH and T2 spectrum proceeded largely as planned. Some work was also done on the D2 spectrum. In the analysis of complicated parts of the spectra a modification of the spectrum in a discharge through 200 mm helium and traces of T2, D2 or TH was very helpful. This modified spectrum showed only bands originating from vibrationless levels at a high rotational temperature. Attempts to obtain the spectrum of T2 free from TH and H2 so far have not been successful, and a modification in the discharge tube is proposed. This modified tube should also be satisfactory for accurate intensity measurements. The analysis of the molecular spectrum of He revealed a noticeable interaction between nuclear spin and orbital angular momentum.

Experimentation with a 5-meter vacuum Ebert Fastie spectrograph (with the basic design by W. G. Fastie and constructed by the Jarrell-Ash Co.) is reported; the experimentation was into very high resolution, particularly in the vacuum ultraviolet. Orders were separated by an order sorter with cross dispersion: above 2000 A a quartz prism was used and below, a grating with a concave mirror. Both order sorters performed adequately. A 600 000 resolving power was achieved. The spectrograph apparently will give in the vacuum UV above 1000 A a resolution and wave number accuracy obtainable only for the visible and adjacent regions. Except for very special light sources, resolution and wave number accuracy are determined by actual line width rather than by performance of the spectrograph., Reference only at DDC Hq. after original copies exhausted.