Oxidation and Reduction of Polycrystalline Cerium Oxide Thin Films in Hydrogen.

This study investigates the oxidation state of ceria thin films' surface and subsurface under 100 mTorr hydrogen using ambient pressure X-ray photoelectron spectroscopy. We examine the influence of the initial oxidation state and sample temperature (25-450 °C) on the interaction with hydrogen. Our findings reveal that the oxidation state during hydrogen interaction involves a complex interplay between oxidizing hydride formation, reducing thermal reduction, and reducing formation of hydroxyls followed by water desorption.

Hydrogen Exchange through Hydrogen Bonding between Methanol and Water in the Adsorbed State on Cu(111).

The interaction between submonolayers of methanol and water on Cu(111) is studied at 95-160 K temperature range with surface-sensitive infrared spectroscopy using isotopically labeled molecules. The initial interaction of methanol with the preadsorbed amorphous solid water at 95 K is through hydrogen-bonding with the dangling hydroxyl groups of water. Upon increasing the temperature up to 140 K, methanol and deuterated water form H-bonded structures which allow hydrogen-deuterium exchange between the hydroxyl group of methanol and the deuterated water.

Clusters of betaine with positive and negative ions: Evidence for the betaine tetramer being magic.

Betaine (Bet) is a pure zwitterion with an extraordinarily large dipole moment, which allows it to form stable clusters in the gas phase of the form XBet, where X is a positive or negative ion. We show here that such clusters have a prominent magic number at N = 4 for all X ions used in this work. Nevertheless, we observe a marked difference in the fragmentation pattern of anionic and cationic clusters: while cationic clusters fragment by evaporating one betaine monomer at a time, fragmentation of anionic clusters is through fission resulting in the emission of one or several betaine molecules.