The Band Spectrum of Boron Fluoride

The spectrum of boron fluoride as excited by the electrodeless discharge has been photographed at both high and low dispersion. Sixteen new bands were observed in the region between $\lambda \lambda 3712$ and 2580A. These bands degrade to the violet; have five head-forming branches, and resemble very closely the third positive bands of CO, a result to be anticipated from the fact that CO and BF both possess ten extranuclear electrons and should therefore have similar electronic configurations. Two systems were found with a common lower electronic level: an $A$ system (${\nu }^{\mathrm{}(0,0)\mathrm{}}=32,020.5\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$) of 12 bands and one isotope band, and a $B$ system (${\nu }^{\mathrm{}(0,0)\mathrm{}}=37,991\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$) of three bands. The constants obtained from the vibrational analysis are: $\omega _e^{}{}_{}{}^{\prime }$, 1631.40 ${\mathrm{cm}}^{-1\mathrm{}}$; $\omega _e^{}{}_{}{}^{\prime \prime }$, 1323.64 ${\mathrm{cm}}^{-1\mathrm{}}$; $x_e^{}{}_{}{}^{\prime }\omega _e^{}{}_{}{}^{\prime }$, 23.10 ${\mathrm{cm}}^{-1\mathrm{}}$; $x_e^{}{}_{}{}^{\prime \prime }\omega _e^{}{}_{}{}^{\prime \prime }$, 9.40 ${\mathrm{cm}}^{-1\mathrm{}}$.