Assignment of the lambda 1369.13 diffuse interstellar absorption band and three other far-ultraviolet interstellar absorption lines to the CH molecule

The three unidentified interstellar lines lambda lambda 1368.74, 1369.13, a nd 1370.87 are here assigned to the CH molecule, including the diffuse inte rstellar band (DIB) at 1369.13 Angstrom. A consistent rotational assignment of the interstellar lines and the 3d-X (2)Pi laboratory spectrum is presen ted. The predominant broadening mechanism of the lines appears to be predis sociation, which is found to be greater for lines with upper levels of d pa rity, including the DIB, than for lines with upper levels of c parity. The oscillator strength of the 3d-X (2)Pi transition is estimated to be f appro ximate to 0.033. Using the theoretical n* dependence of the parameters toge ther with the wavenumber of the observed laboratory Q-form branch, an unide ntified interstellar line at 1270.96 is assigned to the strongest line of t he 4d-X (2)Pi transition of CH.