SPECTROSCOPY OF HIGHLY ROTATIONALLY EXCITED Bal $C^{2}\Pi - X^{2}\Sigma^{+}$

Abstract

A supersonic beam of HI crosses an effusive beam of Ba and the resulting Bal $X^{2}\Sigma^{+}$ product is probed using a single-mode CW ring dye laser at $\sim 550nm$ via laser induced fluorescence of the Bal $C^{2}\Pi - X^{2}\Sigma^{+}$ band system. Under these experimental conditions. Bal $v=0$ product is formed with rotational quantum numbers in excess of 500. For the isolated $P_{2}$ and $P_{12}$ branches of the C - X (0,0) band, single rovibronic transitions with J ranging from $\sim 350$ to $\sim 500$ are readily resolved. Previous $studies^{1}$ employing a thermal oven source provided definitive assignments of the Bal C - X (0,0) band for low J values $(J < 200)$. These data were combined with the line positions obtained in the present study to perform a nonlinear least squares fit to the energy differences calculated from the upper and lower state model Hamiltonians. This permits rotational assignment of the high J transitions. The resulting spectroscopic constants enable a detailed explanation of the observed high-J bandhead features in the Bal $C-X \Delta v = 0$ sequence that characterize the Bal product.