EVIDENCE FOR THE MOLECULAR ORIGIN OF SOME HITHERTO UNIDENTIFIED INTERSTELLAR LINES

In recent years a considerable number of lines of interstellar origin have been discovered by the Mount Wilson observers.1 Several of these have been identified with known atomic lines arising from spectra of Na i, K i, Ca i, and Ti il. However, there have remained unidentified, not only the diffuse lines in the red studied by Merrill and his co-workers2 and that at A.4430 examined by Beals and Blanchet,3 but also five characteristically sharp lines at M 4300.3, 4232.6, 3957.7, 3934.3, and 3874.6, the last of which was only recently found.4 In connection particularly with the diffuse lines, a number of attempts to correlate the wave lengths of the unidentified lines with absorptions of possible interstellar molecules have been made,5 but these have apparently met with little success. It was found by Dunham and Adams6 that only those Ti il lines arising from the lowest 4F3/2 level of the multiple ground state of this atom were observed as interstellar lines. None originating on the aF5/2 level, 0.012 volts above, were detected. Applying these considerations to molecular spectra7 this would