Interaction-region decoupling for deep-well quantum dynamics: Overcoming the interpolation bottleneck and revealing the intrinsic high-energy efficiency.

Deep-well chemical reactions pose a long-standing challenge for rigorous quantum dynamical calculations because of their extended interaction regions. The interaction-region decoupling (IRD) framework based on structured imaginary potentials offers a principled solution, but its practical efficiency has not yet been fully realized due to the prohibitive cost of mutual interpolation. Here, we introduce a block-wise interpolation scheme, in which the interaction region is divided into several spatial blocks and the wave function is interpolated only within the relevant blocks. The resulting IRD-based TDWP approach is applied to the O + OH reaction over a wide range of collision energies. Benchmark calculations show that the block-wise strategy removes the interpolation bottleneck and enables the IRD approach to achieve a speedup of about two orders of magnitude compared with the conventional TDWP method. Moreover, we find that increasing collision energy enhances SIP absorption, allowing for shorter absorbing regions and a reduced effective interaction region, which leads to further improvements in computational efficiency. Our work establishes IRD as a general and efficient framework for the quantum dynamics of complex-forming reactions.