Knowledge Bank

By making use of the sealed discharge tube technique the emission spectra of the $\mathrm{<mrow\; data-mjx-texclass="ORD">28</mrow>}Si32S$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">28</mrow>}Si34S$ molecules have been photographed under moderate an well as high resolutions. The spectra are excited strongly and are entirely free from unwanted spectra. The measured isotope shifts or the bands in the regions 2000-2600A and 3900-6200A which are attributed to the $E\prime \Sigma +-X\prime \Sigma +$ transition have been found to agree with the theoretically calculated shifts, thereby confirming the vibrational assignments of Bredhol et al. Further, satisfactory agreement between the measured and the calculated Isotope shifts of the $D\prime \Sigma -X\prime \Sigma +$ bands (2600-3900A)has been found, in conformity with the vibrational assignments of Barrow and Jevon.