Interferometric Line Shape Modulation in Alkali-Halide Photoabsorption

An ab initio calculation of the photoabsorption spectrum of ground state LiF below the ionic Li++F - threshold predicts a periodic modulation of the predissociation line shapes. Specifically, we predict a periodic reversal of Fano close-quote s line shape asymmetry parameter q . In this case, reversal of the q parameter occurs because of the interference of vibrational wave functions propagating alternatively along diabatic and adiabatic potentials. The interference modulates the predissociation spectrum giving rise to both extremely long-lived resonances and broad window resonances. These anomalous resonances occur periodically on an energy scale greater than the Rydberg energy spacing and are finite in number. copyright 1999 The American Physical Society