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 assis- tance 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 processes

Photoelectron spectra of alkali metal–ammonia microjets: From blue electrolyte to bronze metal

Experimental studies of the electronic structure of excess electrons in liquids—archetypal quantum solutes—have been largely restricted to very dilute electron concentrations. We overcame this limitation by applying soft x-ray photoelectron spectroscopy to characterize excess electrons originating from steadily increasing amounts of alkali metals dissolved in refrigerated liquid ammonia microjets. As concentration rises, a narrow peak at ~2 electron volts, corresponding to vertical photodetachment of localized solvated electrons and dielectrons, transforms continuously into a band with a sharp Fermi edge accompanied by a plasmon peak, characteristic of delocalized metallic electrons. Through our experimental approach combined with ab initio calculations of localized electrons and dielectrons, we obtain a clear picture of the energetics and density of states of the ammoniated electrons over the gradual transition from dilute blue electrolytes to concentrated bronze metallic solutions

High resolution analysis of 32 S18O2 spectra: The ν1 and ν3 interacting bands

Highly accurate, image, ro-vibrational spectrum of S18O2 was recorded with Bruker IFS 120 HR Fourier transform interferometer in the region of 1050–1400 cm−1 where the bands ν1 and ν3 are located. About 1560 and 1840 transitions were assigned in the experimental spectrum with the maximum values of quantum numbers image equal to 65/22 and 58/16 to the bands ν3 and ν1, respectively. The further weighted fit of experimentally assigned transitions was made with the Hamiltonian model which takes into account Coriolis resonance interaction between the vibrational states (100) and (001). To make the ro-vibrational analysis physically more suitable, the initial values of main spectroscopic parameters have been estimated from the values of corresponding parameters of the S16O2 species on the basis of the results of the Isotopic Substitution theory. Finally, the set of 23 spectroscopic parameters obtained from the fit reproduces values of 1292 initial “experimental” ro-vibrational energy levels (about 3400 transitions assigned in the experimental spectrum) with the image. Also, the ground state parameters of the S18O2 molecule were improved

High resolution analysis of 32 S18O2 spectra: The ν1 and ν3 interacting bands

Highly accurate, image, ro-vibrational spectrum of S18O2 was recorded with Bruker IFS 120 HR Fourier transform interferometer in the region of 1050–1400 cm−1 where the bands ν1 and ν3 are located. About 1560 and 1840 transitions were assigned in the experimental spectrum with the maximum values of quantum numbers image equal to 65/22 and 58/16 to the bands ν3 and ν1, respectively. The further weighted fit of experimentally assigned transitions was made with the Hamiltonian model which takes into account Coriolis resonance interaction between the vibrational states (100) and (001). To make the ro-vibrational analysis physically more suitable, the initial values of main spectroscopic parameters have been estimated from the values of corresponding parameters of the S16O2 species on the basis of the results of the Isotopic Substitution theory. Finally, the set of 23 spectroscopic parameters obtained from the fit reproduces values of 1292 initial “experimental” ro-vibrational energy levels (about 3400 transitions assigned in the experimental spectrum) with the image. Also, the ground state parameters of the S18O2 molecule were improved

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

Spectroscopic evidence for a gold-coloured metallic water solution

Insulating materials can in principle be made metallic by applying pressure. In the case of pure water, this is estimated1 to require a pressure of 48 megabar, which is beyond current experimental capabilities and may only exist in the interior of large planets or stars2,3,4. Indeed, recent estimates and experiments indicate that water at pressures accessible in the laboratory will at best be superionic with high protonic conductivity5, but not metallic with conductive electrons1. Here we show that a metallic water solution can be prepared by massive doping with electrons upon reacting water with alkali metals. Although analogous metallic solutions of liquid ammonia with high concentrations of solvated electrons have long been known and characterized6,7,8,9, the explosive interaction between alkali metals and water10,11 has so far only permitted the preparation of aqueous solutions with low, submetallic electron concentrations12,13,14. We found that the explosive behaviour of the water–alkali metal reaction can be suppressed by adsorbing water vapour at a low pressure of about 10$^{−4}$ millibar onto liquid sodium–potassium alloy drops ejected into a vacuum chamber. This set-up leads to the formation of a transient gold-coloured layer of a metallic water solution covering the metal alloy drops. The metallic character of this layer, doped with around 5 × 10$^{21}$ electrons per cubic centimetre, is confirmed using optical reflection and synchrotron X-ray photoelectron spectroscopies