Simultaneous measurement of rotational and translational relaxation by sub‐Doppler optical–optical double resonance spectroscopy: BaO(A 1Σ+)–Ar and BaO(A1Σ+)–CO2

Sub‐Doppler optical–optical double resonance (OODR) spectroscopy is used to correlate BaO(A1Σ+) rotational and translational relaxation induced by collisions with Ar or CO2 in a 0.3–2 Torr Ba+CO2+Ar flame. A selected rovibronic BaO A 1Σ+←X 1Σ+ transition is pumped by the first of two frequency stabilized, 1 MHz bandwidth, cw dye lasers. Collision‐induced level‐to‐level processes in the A 1Σ+ state are monitored with the second laser by excitation of C 1Σ+←A1Σ+ probe transitions and detection of C 1Σ+→X 1Σ+ ultraviolet fluorescence. The dependence of J‐changing collision rates on the initial A 1Σ+ (v=1) rotational level, Jo, is monitored by independent preparation of Jo=0 and Jo=15. For Ar, ‖ΔJ‖=1–20 collision rates are found to be independent of Jo and well represented by the power law, where ΔEr is the change in BaO (A 1Σ+) rotational energy in cm−1; e=ΔEr for Jocollisions a single power law is inadequate to represent Jo=0 and Jo=15 data: Total BaO–Ar J‐changing collision...