Bi- and unimolecular resonances of the collinear reaction F+DBr⇄FDBr⇄FD+Br

The reaction probability function P(v′←v|E) of the bimolecular collinear reaction F + DBr(v)→FD(v′) + Br shows sharp resonance peaks at certain collision energies E_bi. On the other hand, the unimolecular dissociation FDBr*(v₁v₃) → F + DBr(v), FD + DBr(v) exhibits long-lived behavior for particular resonance wave functions ψv₁v₃ at energies E_uni. Good numerical agreement is found in a comparison of bi- and unimolecular resonance energies and lifetimes by two complementary methods: (i) S-matrix propagation in hyperspherical coordinates for the bimolecular reaction; (ii) the diagonally corrected vibrational adiabatic hyperspherical (DIVAH) method to determine unimolecular resonances, coupled with the fast Hankel transform (FHT) method to propagate them in time. The agreement found suggests a correlation between bi- and unimolecular resonances by the reaction mechanism F + DBr(v)⇄FDBr*(v₁v₃)⇄FD(v′) + Br, where the unimolecular resonance states ψv₁v₃ serve as traps or doorway states, blocking or catalyzing the bimolecular reaction.