High-resolution,laser-induced fluorescence spectroscopy of nascent IF: Determination of X- and B-state molecular constants

Nascent IF molecules are prepared in a crossed molecular beam experiment in different vibrational-rotational manifolds of the X¹Σ⁺ electronic ground state using the reactions F + CF₃I → IF + CF₃ and F + ICI → IF + Cl. High-resolution, laser-induced fluorescence spectroscopy is applied for precision measurements of the bandhead structure of 13 transitions of the IF B → X system (0 ≦ v′ ≦ 4, 3 ≦ v″ ≦ 9). A splitting of the resolved ro-vibronic lines of the order of 500 MHz is observed which is due to the nuclear electric quadrupole interaction. Band origins are derived from the excitation spectra in the vicinity of the band heads. Dunham coefficients are presented for the X¹Σ⁺ and the B³Π(O⁺) state, based on a simultaneous fit of the laser-induced fluorescence data obtained in this work, as well as of the microwave spectroscopy data of Tiemann et al. (Z. Naturforsch. a28, 1405–1407) and of original flame emission spectra of Durie (Canad. J. Phys.44, 337–352).