  An alternative methodology to investigate indirect polyatomic processes with
quasi-classical trajectories is proposed, which effectively avoids any binning
or weighting procedure while provides rovibrational resolution. Initial
classical states are started in terms of angle-action variables to closely
match the quantum experimental conditions and later transformed into Cartesian
coordinates, following an algorithm very recently published [J. Chem. Phys.
130, 114103 (2009)]. Trajectories are then propagated using the 'association'
picture, i.e. an inverse dynamics simulation in the spirit of the exit-channel
corrected phase space theory of Hamilton and Brumer [J. Chem. Phys. 82, 595
(1985)], which is shown to be particularly convenient. Finally, an approximate
quasi-classical formula is provided which under general conditions can be used
to add possible rotational structures into the vibrationally-resolved
quasi-classical distributions. To introduce the method and illustrate its
capabilities, correlated translational energy distributions from recent
experiments in the photo-dissociation of ketene at 308 nm [J. Chem. Phys. 124,
014303 (2006)] are investigated. Quite generally, the overall theoretical
algorithm reduces the total number of trajectories to integrate and allows for
fully theoretical predictions of experiments on polyatomics.
