The collinear atom-diatom collision system provides one of the simples
t instances of chaotic or irregular scattering. Classically, irregular
scattering is manifest in the sensitive dependence of post-collision
variables on initial conditions, and quantally, in the appearance of a
dense spectrum of dynamical resonances. We examine the influence of k
inematic factors on such dynamical resonances in collinear (He, H-2(+)
) collisions by computing the transition state spectra for collinear (
He,HD+) and (He,DH+) collisions using the time-dependent quantum mecha
nical approach. The nearest neighbor spacing distribution P(s) and the
spectral rigidity Delta(3)(L) for these resonances suggest that the d
ynamics is predominantly irregular for collinear (He,HD+) and predomin
antly regular for collinear (He, DH+). These findings are reinforced b
y a significantly larger ''correlation hole'' in ensemble averaged sur
vival probability [[(t)]] values for collinear (He, HD+) than for coll
inear (He,DH+). In addition we have also examined measures of classica
l chaos through the dependence of the final vibrational action, n(f),
on the initial vibrational phase phi(i) of the diatom, and Poincare su
rfaces-of-section They show that (He, HD+) collisions are partly chaot
ic over the entire energy range (0-2.78 eV) while (He, DH+) collisions
, in contrast, are highly regular at collision energies below the clas
sical threshold for reaction. Above the threshold, the scattering rema
ins regular for initial vibrational states v = 0 and 1 of DH+.