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, v=2) BY NOVEL LASER PHOTOIONIZATION TECHNIQUE IN AIR AT ATMOSPHERIC PRESSURE.
JONATHAN D. UMBEL, STEVEN F. ADAMS, CHARLES A. DEJOSEPH JR., Propulsion Directorate, Air Force Research Laboratory, WPAFB, OH 45433.
We have used pulsed laser photoionization of dry atmospheric air for the analysis of the O2(X3
C3
) excitation spectrum and improved characterization of the O2(C3
) Ryberg state. This 3
Ryberg state is generally very diffuse due to predissociation, but using this method, reasonable resolution in the rotational structure of the v=2 level was achieved. A simulated O2(X3
C3
) excitation spectrum was calculated for line position, intensity, and linewidth that agreed very well with the experiment, providing values for
0, Beff, and Deff for the F1, F2, and F3 subbands of O2(C3
, v=2). The photoionization technique involved a combination of resonant-enhanced multi-photon ionization (REMPI), collisional excitation, and laser-induced fluorescence. A focused, ultraviolet laser pulse was used to excite the O2(X3
C3
) resonant transition. The near coincident energy between the O2(C3
, v=2) state and the N2(a/ 1
-u, v=1) state resulted in rapid collisional transfer of energy to the N2(a') state. The N2(a') molecules were then photoionized by the same laser pulse to the N2+(B) state, producing an easily observable fluorescence at 391 nm. By scanning the laser wavelength while observing the 391 nm fluoresence, details of the O2(C3
) Ryberg state could be studied.