Knowledge Bank

The emission spectra of ScH and ScD have been observed in the 480mm- 2.5 $\mu$m spectral region using a Fourier transform spectrometer. The molecules were excited in a scandium hollow cathode lamp operated with neon gas and a trace of hydrogen or deuterium. Three transitions with a common lower state, assigned as the ground $X1\Sigma +$ state, have been observed in the near infrared and visible regions. The ScH brands with 0-0 band origins at 5404, 13574 and $20547cm-1$ have been assigned as the $B1\Pi -X1\Sigma +,C1\Sigma +-X1\Sigma +$ and $G1\Pi -X1\Sigma +$ transitions, respectiveley. A rotational analysis of the 0-0, 1-1, 1-0 and 2-1 bands of the $B1\Pi +-X1\Sigma +$ systems, the 0-0 and 1-1 bands of the $C1\Sigma +-X1\Sigma +$ system and the 0-0 band of the $G1\Pi -X1\Sigma +$ system has been obtained. The principal molecular constants for the $X1\Sigma +$ state of Sch are: $\Delta G(1/2)=1546.9730(14)cm-1,Be=5.425432(48)cm-1,\alpha e=0.124802(84)cm-1$ and $re=10775427(8)$ \AA The corresponding band systems of ScD have also been analyzed. A rotational analysis of the 0-0, 1-1 and 1-0 bands of the $B1\Pi -X1\Sigma +$ system, the 0-0, 1-1, 0-1 and 1-2 bands of the $C1\Sigma +-X1\Sigma +$ system and the 0-0 band of the $G1\Pi -X1\Sigma +$ system has been obtained. The equilibrium molecular constants determined for the ground state of ScD are: $\omega e=1141.2650(31)$ $cm-1$, $\omega exe=12.3799(15)$ $cm-1$, $B=2.787432(41)$ $\alpha e=0.045321(73)$ $cm-1$ and $re=1.771219(13)\backslash AA$ The ScH assignments are supported by recent theoretical predictions made by Anglada et al. [Mol. Phys. 66, 541 (1989)] as well as the experimental results available for ScF and the isovalent YH and LaH molecules. Although some unassigned bands have been attributed to ScH and ScD by previous workers, there have been no previous analyses of ScH or ScD spectra.