Quantum scattering with energy-filtered plane wave packets: Visualizing the F+HD "ridge" mechanism

We develop a very simple, previously neglected, idea for enhancing the power of quantum wave packet calculations to interpret chemical reactions. This is that, once the energy-domain wave function is calculated, an infinite variety of time-dependent wave packets may be recovered from it, simply by multiplying by an energy filter and taking the Fourier transform. Each packet corresponds to a different initial wave packet along the scattering coordinate. We show that, when incorporated into the plane wave packet method [J. Chem. Phys. 2002, 117, 4623], the filters can isolate features in the differential cross section and generate separate wave packets visualizing the dynamics of each feature. The filters also enable one to focus the wave packets, so as to minimize artifacts caused by spreading. We demonstrate these ideas on the F + HD reaction, by isolating the low energy ridge from the differential cross section and generating a focused plane wave packet that visualizes its dynamics. We find that the ridge is produced by a "Catherine wheel" rotation and decay of the FHD complex through about 180degrees.