Sub-Doppler optical-optical double-resonance spectroscopy of BaO: Electronic structure in the 4-eV region

Abstract

Vibronic levels of BaO with energies in the 4-eV region are observed by cw dye laser optical-optical double-resonance (OODR) spectroscopy. Sub-Doppler, 0.003-cm −1-precision OODR spectra of the C 1Σ +- A 1Σ + (1,0), (2,1), and (3,1) bands are recorded and rotationally analyzed, and numerous perturbations detected in the C 1Σ + state are partially analyzed. Broad bandwidth, 0.2-cm −1-precision, cw dye laser OODR spectra of the C 1Σ +- A 1Σ + (0,0) and (4,2) bands as well as the (3,2), (4,2), (5,3), and (6,3) bands of a new D 1Σ +- A 1Σ + system are obtained and rotationally analyzed. Additional bandheads and several new but incompletely characterized electronic states, B 1Π, E 1Σ +, and c( 3 Π 0) , are also reported. Spectroscopic constants determined for C 1Σ + and D 1Σ + are: C 1 Σ + D 1 Σ + T e ( cm −1 ) 32 872.7 (30) 32 835 (6) ω e ( cm −1 ) 436.0 (8) 403.6 (28) ω e x e ( cm −1 ) 0.90 (16) 3.8 (3) ω e y e ( cm −1 ) 0.041 (10) — B e ( cm −1 ) 0.2397 (6) 0.2197 (20) α e ( cm −1 ) 0.00270 (18) 0.0015 (4) R e ( A ̊ ) 2.2151 (28) 2.314 (10) Quantitites in parentheses are 1σ uncertainties in the last digit.