Studies of labile molecules with a tunable dye laser. Laser excitation spectrum of BrF ( B3Π(0 +)- X1Σ +)

The B³Π(0 ⁺) ← X¹Σ ⁺ absorption spectrum of BrF (4850-5200 Å) has been observed by the technique of laser emission spectroscopy. Fluorescence was excited by a pulsed, scannable dye laser with a 0.1 Å bandwidth. Rotational analysis has been carried out for six bands of the v″ = 0 progression (8 ≥ v' ≥ 3) of ⁷⁹BrF and ⁸¹BrF. Rotational constants for the B³Π(0 ⁺) state are reported for the first time. RKR potential energy curves for both states, and an array of Franck-Condon factors and r-centroids for the transition, have been calculated. Bands with v' > 8 were not observed in fluorescence owing to the onset of predissociation near J' = 28 of the v' = 8 level. An upper limit for the ground state dissociation energy is D₀″ (BrF, X¹Σ ⁺) ≤ 20 880 cm ^-1.