Fig. 1
Scheme of the interplay between electron-phonon-coupling (EPC) and laser-induced potential energy surface (PES) changes: Electronic bonds are visualized as springs between the ions that are drawn as grey balls. In addition, the electrons move through the crystal and collide with the ions. These moving electrons are drawn as small balls with black arrows indicating the actual velocity. (A) Before the fs-laser excitation the electronic temperature is at 300 K, so that the electrons have a low velocity resulting in infrequent collisions with ions, which vibrate around their equilibrium positions. (B) After the femtosecond laser excitation the electrons exhibit a high temperature leading to significant changes of interatomic bonding (red springs) and strong forces acting on the ions. This represents the change of the PES. In addition, the now very fast moving electrons perform strong collisions with the ions (strong EPC).
