Knowledge Bank

New data have been obtained on the electronic transitions of AlCl between 1600{\AA} and 4200{\AA} by both emission and absorption techniques. Studies of the $A1\Pi -X1\sum +$ transition in absorption have yielded rotational structure for the 0-0 band and other low-lying levels, unlike previous studies of the emission spectrum which had resolvable rotational lines only for $v>3$ in both states. The following constants (in $cm-1$) were obtained for the 0-0 band after fixing the lower state constants to those obtained from the microwave $spectrum1:\nu oo=38237.6,Bo\prime =0.24407$,and $Do\prime =2.99\times 10-7$ The transition occurring between 3900 {\AA} and 4200 {\AA}, previously assigned as the a $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi -X 1\Sigma +$ $transition2$, has been observed in emission with sufficient resolution to estimate the following constants (in $cm-1$): $\nu oo=24614.3, \omega e=527,\omega exe=3.1,Bo\prime =0.2502,$ and $Do\prime =1.56\times 10-7$. The vacuum ultraviolet spectrum of AlCl has been seen in emission and, for the first time in absorption from 1600 {\AA}-1870 {\AA}. Five vibrational progressions have been observed, three of which are consistent with a progression in the ground state. These system appear to be quite distinct from those reported previously between 1820 {\AA} and 2075 {\AA} by Reddy and $Rao3$.