Ammonia cluster anions and their relationship to ammoniated (solvated) electrons: The photoelectron spectra of (NH3)n=41–1100−

Abstract

A theoretical prediction on intermolecular monoelectron dihydrogen bond H e H in the cluster anion ( FH ) 2 {e}( HF ) 2We report the negative ion photoelectron spectra of (NH 3 ) nϭ41-1100 Ϫ , recorded using 2.540 eV photons. The largest cluster anion in this series has a diameter of approximately 4.3 nm. The vertical detachment energies ͑VDEs͒ of these cluster anions increase smoothly from 0.55 eV for nϭ41 to 1.05 eV for nϭ1100. The VDEs throughout this size range are linear with n Ϫ1/3 and extrapolate to a VDE (nϭϱ) value, which is very close to the measured photoelectric threshold energy of condensed phase ammoniated electrons. The linear extrapolation of this data to an analogous condensed phase property implies that these cluster anions are gas-phase counterparts to ammoniated electrons, i.e., they are embryonic forms of ammoniated electrons which will mature with increasing cluster size to become condensed phase-solvated electrons. The VDE data further implies that these embryonic ammoniated electrons were generated in solid ammonia environments, consistent with the source conditions under which they were produced.

Dynamics of Electrons in Ammonia Cages: The Discovery System of Solvation

“…[35,36] A slope of 3.0 eV is also close to that of 3.08 eV obtained using the parameters of B for ammonia. [21] For (NH 3 ) 50 À , the VDE measured in this work is 0.62 eV, which is consistent with Bowen's reported value of 0.59 AE 0.1 eV. [21] A single peak was observed for the large size clusters, but for the smaller clusters some structure in the PE spectra is evident.…”

“…[33] Using a dielectric continuum model, [21,25,34] where the molecular cluster is described by a dielectric cavity of radius R = r s n À1/3 (r s is the mean radius of the molecular constituent), gives VDE(R) = VDE ( The slope and intercept of the linear plot agree well with those reported by the Bowen and co-workers. [21] The intercept is 1.5 eV consistent with the value of 1.27-1.45 eV obtained by photoelectric electron threshold measurement in bulk liquid. [35,36] A slope of 3.0 eV is also close to that of 3.08 eV obtained using the parameters of B for ammonia.…”

“…The cluster distribution obtained here ( Figure 1) shows that the lowest n value is 13, compared to 30 [17,18] and 41, [21] and that the distribution is more shifted toward the smaller size clusters. This shifting originates from our utilization of a high pressure nozzle, which is known to provide a very efficient cooling.…”

“…[17][18][19][20] Bowen and co-workers, [21] in their study using PE spectroscopy, showed a new range of cluster size, n = 41-1100, and, as discussed below, indicated their embryonic relationship to solvated electrons, especially as n increases. Neumark and his co-workers, [22] for the I À A C H T U N G T R E N N U N G (NH 3 ) n , with n = 4-15, system were able to monitor the dynamics following the charge transfer to the solvent.…”

Femtosecond Relaxation Dynamics of Solvated Electrons in Liquid Ammonia

“…In fact, it is even faster than the vibrational lifetime of a water OH stretching vibration, and faster than the timescale for vibrational energy randomization in bulk liquid water. [28] However, certain molecular dynamical processes, such as translational and rotational diffusion, are known to occur at the same temperature about an order of magnitude faster in ammonia than in water, although the molecular masses are similar and the moments of inertia are higher for NH 3 . [29] Interestingly, the cooling time observed here agrees rather well with the mean hydrogen-bond lifetime extracted from Car-Parrinello molecular dynamics simulations using an improved density functional that can also account for nonlinear hydrogen bonding contacts.…”