Interferometric Line Shape Modulation in Alkali-Halide Photoabsorption

An ab initio calculation of the photoabsorption spectrum of ground state LiF below the ionic Li 1 F threshold predicts a periodic modulation of the predissociation line shapes. Specifically, we predict a periodic reversal of Fano’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. [S0031-9007(99)08649-4]