Knowledge Bank

Rotation-vibration spectra of MgH, CaH and their deuterated forms in the $X2\Sigma +$ state have been measured using tunable infrared diode lasers. The hydrides were produced in a D.C. discharge of $H2$ or $D2$ over heated magnesium or calcium. Transitions from the fundamental bands and from hot bands $(v=2\leftarrow 1$ for MgH, and up to $v=4\leftarrow 3$ for CaH) were observed. The spectra were analyzed to determine accurate set of molecular parameters, either for each vibrational state or as Dunham coefficients. The mass dependance of the molecular parameters is examined in terms of possible breakdown of the Born-Oppenheimer approximation.