When an excited atom is embedded into an environment, novel relaxation
pathways can emerge that are absent for isolated atoms. A well-known example
is interatomic Coulombic decay, where an excited atom relaxes by transferring
its excess energy to another atom in the environment, leading to its
ionization. Such processes have been observed in clusters ionized by extreme-
ultraviolet and X-ray lasers. Here, we report on a correlated electronic decay
process that occurs following nanoplasma formation and Rydberg atom generation
in the ionization of clusters by intense, non-resonant infrared laser fields.
Relaxation of the Rydberg states and transfer of the available electronic
energy to adjacent electrons in Rydberg states or quasifree electrons in the
expanding nanoplasma leaves a distinct signature in the electron kinetic
energy spectrum. These so far unobserved electron-correlation-driven energy
transfer processes may play a significant role in the response of any nano-
scale system to intense laser light.