Knowledge Bank

The 3100 \AA system or $CS2$ has been photographed in absorption with a 35 ft. grating spectrograph. Multiple reflection mirrors have been used in the absorption cell to obtain path lengths of up to 100 meters. The spectrum extends from 2700 \AA to 4000 \AA. The long wavelength end of the spectrum consists of regular progressions involving excitation of the bending frequency of the upper state. In addition to the bending frequency, one quantum of the symmetric stretching frequency of the upper state is also excited in some progressions. The lower states range from the ground state up to $5\nu 2$ and the bands have the appearance of $\Sigma -\Sigma ,\Pi -\Pi ,A-A$, and $\Phi -\Phi$ bands. A detailed study of the vibrational and rotational structure shows that the molecule is non-linear in the upper state.