High-resolution laser spectroscopy on H2 at 97–98 nm

A narrowband tunable eXtreme UltraViolet (XUV) laser source is used for a high resolution study of the Lyman (B ¹ _u ⁺ X ¹ _g ⁺ ) band system of molecular hydrogen. Seven rotational transitions of two vibrational bands, (10,0) and (11,0), in the wavelength range from 97.2–98.3 nm have been investigated for the first time under sub-Doppler molecular beam conditions. A calibration procedure using the I₂ standard in the visible yielded an absolute frequency accuracy of 0.02 cm^–1. The obtained H₂ transition frequencies provide a calibration standard in the extreme ultraviolet wavelength region.     

A study of the gold/aqueous electrolyte interphase by modulated reflection spectroscopy

The admittance and differential reflectivity of an electrode of polycrystalline gold in contact with aqueous 0.02 M NaF, KClO₄, 0.01 M Na₂SO₄ and KCl have been measured in the range of potential where the electrode is ideally polarized (?0.7 V to 0.8 V NHE). In NaF and KClO₄ evidence was obtained for the compression of the adsorbed layer of water. The increase of the number of water molecules, with respect to the number in the least original state (at?4μC cm^?2), is 3% at +8 μC cm^?2 and at?17 μC cm^?2. At the potential of zero charge the water dipoles are oriented preferentially with the oxygen towards the metal. In KCl the optical measurements confirm the existence of two types of Au?Cl^? interaction and the covalent character of the bond at the most positive charges.     

ESI‐MS/MS of expanded porphyrins: a look into their structure and aromaticity

Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd.     

Adsorption of ethyl ether on polycrystal and the (110) single crystal face of gold by admittance measurements and modulated reflection spectroscopy

The adsorption of ethyl ether on polycrystalline and on (110) gold electrodes has been studied by simultaneous measurements of differential capacity and modulated electroreflectance (ER) in aqueous solutions of 0.02 M NaF containing various concentrations of ethyl ether. The results indicate that the adsorption can be studied only at negative charges, the behaviour at positive charges being masked by the oxidation of ether. A comparison of our capacity curves with the data obtained for Hg would indicate that the ether molecules are less strongly adsorbed on Au than on Hg. The ER measurements show that there is a proportionality between the amount adsorbed and the reflectivity change, and confirms that a simple interfacial model may be used to evaluate the amount adsorbed. Qualitative analysis of the ER spectra reveal that the adsorbed layer exhibits transparent optical properties and displays anisotropic characteristics in the adsorption—desorption region, probably due to the sudden change in the layer structure. Furthermore, the ER spectra provide evidence for the absence of any chemical interaction between gold and ether molecules.