| Abstract | The three unidentified interstellar lines λλ1368.74, 1369.13, and 1370.87 are here assigned to the CH molecule, including the diffuse interstellar band (DIB) at 1369.13 Å. A consistent rotational assignment of the interstellar lines and the 3d-X 2Π laboratory spectrum is presented. The predominant broadening mechanism of the lines appears to be predissociation, which is found to be greater for lines with upper levels of d parity, including the DIB, than for lines with upper levels of c parity. The oscillator strength of the 3d-X 2Π transition is estimated to be f ≈ 0.033. Using the theoretical n* dependence of the parameters together with the wavenumber of the observed laboratory Q-form branch, an unidentified interstellar line at 1270.96 Å is assigned to the strongest line of the 4d-X 2Π transition of CH. |
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