Semi-classical Monte Carlo path integration without root searches

A Monte Carlo procedure was developed for numerical path integration using the time-dependent propagator of Van Vleck and Gutzwiller. The work of Heller [J. Chem. Phys. 94 (1991) 2723] was reformulated in the style of a classical trajectory computation with stochastic samplings of the initial conditions, which further moderates the singularities at caustics. Numerical tests in one-dimension showed that the approach is accurate and workable for molecular dynamical calculations.