Oscillations in Total Photodetachment Cross Sections of a Triatomic Anion

The total photodetachment cross section of a linear triatomic anion is derived for arbitrary laser polarization direction. The cross section is shown to be strongly oscillatory when the laser polarization direction is parallel to the axis of the system; the oscillation amplitude decreases and vanishes as the angle between the laser polarization and the anion axis increases and becomes perpendicular to the axis. The average cross section over the orientations of the triatomic system is also obtained. The cross section of the triatomic anion is compared with the cross section of a two-center system. We find there are two oscillation frequencies in the triatomic anion in contrast to only one oscillation frequency in the two-center case. Closed-orbit theory is used to explain the oscillations. (atomic and molecular physics)