Knowledge Bank

The $4f\to 5s$ transition of ArD is observed in $Ar/D2$ discharges as a band near $4830\backslash AA1(\nu 00=20682cm-1)$ with O, Q and S-form branches. On the basis of a preliminary rotational analysis of this band, the transitions $4f\to 3d\sigma ,4f\to 3d\pi$, and $4f\to 3d\delta$ to the three $components2-4$ of the 3d complex could be assigned to bands at 4371, 7666 and $6045cm-1$, respectively. These bands give information on components of the 4f complex not seen in the $4f\to 5s$ band. The 4f complex is found to be a good example of Hund's case (d), with R = 0 splittings that are predominantly of second-rank tensor type with the coefficient of $\lambda 2$ equal to $16.5cm-1$. A number of small perturbations are probably due to vibrational levels of other electronic states, but two larger perturbations near R = 11 and R = 24 are attributed to v = 0 of the $4d\delta$ and $4d\sigma$ states, respectively. The quantum defects of the 4f and other states will be discussed in terms of the properties of the $ArH+$ or $ArD+$ core, including the l-mixing effects of the core electric dipole $moment5$.