Experimental Study of Highly Excited ¹Π_g and ¹Σ_g⁺States of the Cesium Dimer

We report the results of an experimental study of highly excited ¹Π_g and ¹Σ_g⁺ electronic states of the ¹³³Cs₂ dimer. The rovibrational structure of these states was probed using the optical-optical double resonance (OODR) technique in which ¹³³Cs₂ molecules from thermally populated levels in the X¹Σ_g⁺ ground state were excited through intermediate levels from either the B¹Π_u state or the mixed A¹Σ⁺_u ∼ b³Π_u states. The probe laser resonance frequencies were determined by detecting laser induced fluorescence from the target states to the ground a³Σ_u⁺ triplet state. These resonance frequencies were used to calculate the rovibronic term values, which were in turn used to construct potential energy curves for each of the electronic states with the Rydberg-Klein-Rees method. The observed states were identified as ¹Π_g and ¹Σ_g⁺ electronic states based on the selection rules for dipole allowed transitions that the line patterns in the recorded excitation spectra followed.