Rotational analysis of visible bands of nitrogen dioxide using polarization spectroscopy

Polarization labeling spectroscopy is used to simplify the visible absorption spectrum of NO₂. State-selected spectra of the ²B₂-²A₁ transition in the range 16 600–17 000 and 17 350–17 850 cm^?1 are developed using a narrow-band pump operated (1) near 545 nm, where the pumped transitions also belong to the ²B₂ system, and (2) near 436 nm on a selected transition of the ²B₁-²A₁ (Douglas-Huber) band system. Rotational analyses are given for the K_a = 0 and K_a = 1 subbands of 11 vibronic bands and limited observations reported for the K_a = 0 or 1 manifold of a further 8 bands. Polarization-labeling experiments within the ²B₁-²A₁ band system are also described.