Variational basis-set calculations of accurate quantum mechanical reaction probabilities

We have formulated and implemented a variational method for quantum mechanical reactive scattering calculations using square integrable (ℒ²) basis sets to expand the reactive amplitude density. We demonstrate the new method by presenting two calculations for the three-dimensional H + H₂ reaction. In the first we show that variational calculations with a sine basis converge to the same reaction probabilities in the threshold region as our previous calculations performed with the method of moments and a distributed Gaussian basis. In the second we show that variational calculations with a multichannel distortion potential may be converged with only 2-4 basis functions per channel! We report very well converged reaction probabilities for two different potential energy surfaces that may serve as benchmarks for future studies.