THE ABSORPTION SPECTRA OF FLUORINE AND HYDROGEN FLUORIDE IN THE VACUUM ULTRAVIOLET

Abstract

“Absorption spectra of $F_{2}$ and HF have been obtained in a flow system with no windows at wave lengths down to 750A. with a l-meter normal incidence vacuum spectrograph. A Lyman discharge tube was used from the background. The same absorptions that occur in HCI, HBr and HI also occur in HF, but at shorter wave lengths. A continuum at 1280A. in HF is followed by two progressions. A Rydberg series of bands begins at 1137A, and converges to an ionization potential of 12.6 cv. The absorption of $F_{2}$ begins with a V, N-transition around $99,000 cm^{-1}$ which shows a vibrational spacing of $420 cm^{-1}$. A Rydberg series of bands, accompanied by vibrational progressions, begins at 952.3A, and converges to a limit at 15.7 cv for the ionization potential of $F_{2}$. A progression of at least 3 bands beginning at 874A. converges rapidly to a dissociation limit of $3800 \pm 300$ $cm^{-1}$, and atomic products which lie slightly over $105,000 cm^{-1}$ above the ground atomic state. The dissociation products can correspond to any of 4 combinations from multiplets whose overall splitting is $700 cm^{-1}$. The dissociation energy of $F_{2}$ is then to be chosen from the values 36.6, 37.5 or 38.6 k cal/mole, each $\pm 1$ k cal/mole. The ions $F_{3}^{+}$ and $HF^{+}$ are both more stable than the neutral molecules.”