coupledchannels

Coupled channels is a theoretical framework used in quantum mechanics to describe the behavior of a quantum system that can transition between different internal states. This approach is particularly relevant in atomic and molecular physics, where particles can exist in various energy levels or rotational states. When a system has multiple possible outcomes or final states, the evolution of the wavefunction for one state is not independent of the others. The term "coupled" signifies that these different states influence each other's dynamics.

The coupled channels method mathematically represents this interaction by solving a set of differential equations, where each equation describes the amplitude of the system being in a particular channel or state. These equations are linked by coupling terms that quantify the transitions between states. This is often used in scattering problems, where an incoming particle interacts with a target and can be scattered into different internal states of the target or the particle itself. By solving these coupled equations, one can determine the probabilities of these various scattering outcomes.

Applications of the coupled channels method include understanding phenomena like electron-molecule scattering, atom-atom collisions, and molecular photodissociation. It provides a more accurate description than simpler models that treat states independently, especially when the energy differences between states are small or the interaction potential strongly mixes them. The complexity of the coupled channels approach grows with the number of states considered, making it computationally intensive for systems with many possible internal configurations.