Observation of intermolecular Coulombic decay and shake up satellites in liquid ammonia

We report the first nitrogen 1s Auger Meitner electron spectrum from a liquid ammonia microjet at a temperature of 223 K 50 C and compare it with the simultaneously measured spectrum for gas phase ammonia. The spectra from both phases are interpreted with the assistance of high level electronic structure and ab initio molecular dynamics calculations. In addition to the regular Auger Meitner electron features, we observe electron emission at kinetic energies of 374 388 eV, above the leading Auger Meitner peak 3a12 . Based on the electronic structure calculations, we assign this peak to a shake up satellite in the gas phase, i.e., Auger Meitner emission from an intermediate state with additional valence excitation present. The high energy contribution is significantly enhanced in the liquid phase. We consider various mechanisms contributing to this feature. First, in analogy with other hydrogen bonded liquids noticeably water , the high energy signal may be a signature for an ultrafast proton transfer taking place before the electronic decay proton transfer mediated charge separation . The ab initio dynamical calculations show, however, that such a process is much slower than electronic decay and is, thus, very unlikely. Next, we consider a non local version of the Auger Meitner decay, the Intermolecular Coulombic Decay. The electronic structure calculations support an important contribution of this purely electronic mechanism. Finally, we discuss a non local enhancement of the shake up processe