Hydration Process of Na₂^- in Small Water Clusters:  Photoelectron Spectroscopy and Theoretical Study of Na₂^-(H₂O)_n

Abstract

Photoelectron spectroscopy (PES) of Na2- (H2O)n (n < or = 6) was investigated to examine the solvation of sodium aggregates in small water clusters. The PES bands for the transitions from the anion to the neutral ground and first excited states derived from Na2 (1(1)Sigmag+) and Na2 (1(3)Sigmau+) shifted gradually to the blue, and those to the higher-excited states correlated to the 3(2)S + 3(2)P asymptote dropped down rapidly to the red and almost degenerated on the 1(3)Sigmau+-type band at n = 4. Quantum chemical calculations for n up to 3 showed that the spectra can be ascribed to structures where one of the Na atoms is selectively hydrated. From the electron distributions, it is found that the Na- -Na+(H2O)n- -type electronic state grows with increasing cluster size, which can be regarded as a sign of the solvation of Na2- with ionization of the hydrated Na.

An infrared spectroscopic and theoretical study on (CH3)3N–H+–(H2O)n, n = 1–22: highly polarized hydrogen bond networks of hydrated clusters

“…A number of spectroscopic and theoretical studies on hydrated cation-anion clusters have been reported, and a variety of water H-bond network structures have been found. [4][5][6][7][8][9][10][11][12][13][14][15] When a water network is in contact with a charged species through only a single water site, the feature of the polarized water network would be most prominent. An example is the small water anions (H 2 O) 5,6…”

“…16 Such an example, however, has been rarely found in hydration of cations or protonated species because multiple coordination is formed (this is typical in hydration of metal cations) or intra-cluster proton transfer to the water moiety occurs with increasing cluster size. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] To study the microscopic nature of highly polarized water networks, protonated trimethylamine-water clusters TMA-H + -(H 2 O) n are of great interest. In H-bond networks, TMA can play only the role of a single proton acceptor.…”

Microsolvation and Protonation Effects on Geometric and Electronic Structures of Tryptophan and Tryptophan-Containing Dipeptides

“…In the trap, the buffer gas filled in the entire region at a well-defined temperature and pressure thermalizes the trapped ions by multiple collisions as a thermal bath. We have been investigating microscopic solvation process in clusters using spectroscopic methods as a function of cluster size. ,− In order to conduct a spectroscopic study of gas-phase cluster ions as a function of temperature, we constructed a photodissociation spectrometer containing the temperature-controlled multipole ion trap and a spray ionization source and studied the structure and reactivity of cold protonated peptides …”

“…We have been investigating microscopic solvation process in clusters using spectroscopic methods as a function of cluster size. 6,[9][10][11][12][13][14] In order to conduct a spectroscopic study of gas-phase cluster ions as a function of temperature, we constructed a photodissociation spectrometer containing the temperature-controlled multipole ion trap and a spray ionization source and studied the structure and reactivity of cold protonated peptides. 15 Primary and secondary structures of polypeptides are one of the important factors in the characterization of physical and chemical properties of biological molecules.…”

Microsolvation of sodium ion in acetonitrile clusters: Structure and energetic trend by first principle study

“…Compared to water, neat acetonitrile liquid is much less structured, the orientation of any given molecule being correlated only with those of its immediate neighbors [42][43][44]. The solvation of ions in water [12][13][14][15][16][17][18][19][20] is determined by both the large dipole moment of water and also the strong water structure; however the solvation in acetonitrile is expected to be different because acetonitrile have even higher dipole moment but strong internal structure is not there. Thus, it is worth to investigate solvation of ion in acetonitrile for its qualities as a solvent.…”