PHOTOABSORPTION AND FLUORESCENCE SPECTROSCOPY OF BF3 IN THE EXTREME-VACUUM-ULTRAVIOLET REGION

Absorption and fluorescence cross sections of BF3 were measured in the 45 113-nm region. Partial ionization cross sections are derived from the absorption cross section and the known branching ratios and then compared with theoretical calculations. The absorption spectrum shows many vibrational progressions and broad bands that are attributed to the Rydberg and/or valence transitions. Fluorescence from excited BF2* is observed from photoexcitation of BF3. The fluorescence quantum yield shows two repulsive excited states that give maximum yields of 34% at 88 nm and 20% at 96 nm. These two states produce four BF2* emission bands that are distinguished by different fluorescence spectra and radiative lifetimes. The photoexcitation processes that lead to fluorescence and ionization are discussed. © 1990 The American Physical Society.