Rate coefficients for energy-pooling collisions between low-lying excited states of Ba have been measured. The 6s6p${(}^3$${\mathit{P}}_1$) level in Ba is pumped by a cw diode laser, and radiative decay and collisions with buffer-gas atoms also populate the 5d6s${(}^1$D) and 5d6s${(}^3$D) metastable levels. The densities of these low-lying excited states are measured by the absorption of lines from a Ba hollow-cathode lamp, and the states populated by energy-pooling collisions are studied by comparing their fluorescence intensity to that of the laser-excited level. The rate coefficients are on the order of gas-kinetic rates, and they are not strongly dependent on energy defect, spin changes, or angular-momentum changes.

• Received 7 March 1994

DOI:https://doi.org/10.1103/PhysRevA.50.1292