Dispersion forces between molecules with one or both molecules excited.

@article{Power1995DispersionFB,
  title={Dispersion forces between molecules with one or both molecules excited.},
  author={Power and Thirunamachandran},
  journal={Physical review. A, Atomic, molecular, and optical physics},
  year={1995},
  volume={51 5},
  pages={3660-3666}
}