Knowledge Bank

The $A2\Pi r-X2\Sigma +$ system of MgCl molecule (360-380 nm) has been recorded on BOMEM DA8 Fourier transform spectrometer at an apodized resolution of $0.035cm-1$. The spectra have been excited under flowing conditions in a demountable stainless steel hollow cathode lamp (400 V, 250 mA) containing anhydrous $MgCl2$ and Ar. The resulting spectra are very intense and 0-0, 1-1 and 1-0 bands of $A2\Pi 1/2-X2\Sigma +$ sub-transition and 0-0 band of $A2\Pi 3/2-X2\Sigma +$ sub-transition have been recorded and rotationally analyzed. Molecular constants have been derived using a least-squares fit programme in which optical $dataa$ of 0-1 and 0-2 bands ($A2\Pi 1/2-X2\Sigma +$) was also included. The $\Lambda$-doubling constants in the v = 0, 1 levels of the sub-state $A2\Pi 1/2$ are as expected, i.e. $p1>p0$, whereas it is found that the spin-doubling constants of the v = 0, 1, 2 levels of the ground state decrease with the increase in v, i.e., $\gamma 0>\gamma 1>\gamma 2$. This is indicative of presence of some nearby state, influencing the spin-doubling in the ground state. The final results of the rotational analysis will be presented.