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Excitation of HeNe by synchrotron light just below the frequency of the 1s→3p transition of isolated He has been recently shown to be followed by resonant interatomic Coulombic decay (ICD). The vibrationally resolved widths of the ICD states were extracted with high precision from the photoion spectra. In this paper, we report the results of ab initio calculations of these widths. We show that interaction between electronic states at about the equilibrium distance of HeNe makes dark states of He accessible for the photoexcitation and subsequent electronic decay.Moreover, the values of the calculated widths are shown to be strongly sensitive to the presence of the non-adiabatic coupling between the electronic states participating in the decay. Therefore, only by considering the complete manifold of interacting decaying electronic states a good agreement between the measured and computed ICD widths can be achieved. [ABSTRACT FROM AUTHOR]

Excitation of two identical species in a cluster by the absorption of two photons of the same energy is strongly suppressed since the excitation of one subunit blocks the excitation of the other one due to the binding Coulomb interaction. Here, we propose a very efficient way to overcome this blockade in producing doubly excited homoatomic clusters by a single intense laser pulse. For Ne2 it is explicitly demonstrated that the optimal carrier frequency of the pulse is given by half of the target state's energy, which allows one to doubly excite more than half of the dimers at moderate field intensities. These dimers then undergo ultrafast interatomic decay bringing one Ne to its ground state and ionizing the other one. The reported ab initio electron spectra present reliable predictions for future experiments by strong laser pulses. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]