Long-range electrostatic forces in the coadsorption of CH3Cl and water

Compression and caging of CD3Cl by H2O layers on Ru(001)

“…20 CD 3 Cl were deposited first at 82 K, and then increasing coverages of water were added on top. ͑In a previous work by Maschhoff et al 9 the adsorption order was reversed, resulting in a completely different behavior.͒ The CD 3 Cl TPD signal shows a complex dependence on water coverage, but the total uptake of the methyl chloride remains constant within 10%, as determined by integrating the area under the TPD peaks. Water molecules repel the CD 3 Cl coadsorbates out of their normal adsorption sites, squeezing them into a gradually more densely packed phase.…”

“…The goal of the study to be presented below is to explore the unique outcome of strong electrostatic interactions among repelling (CD 3 Cl) and attracting (H 2 O) molecules on a smooth metallic surface-Ru͑001͒, on which the interaction of the separate molecules have been studied extensively. 6 -8,16,17 In one instance, this combination of molecules has been studied on top of Cu͑110͒, 9 with the sole interest, however, in the adsorption properties and characteristics of CH 3 Cl on top of preadsorbed water. A different study used D 2 O layers as spacers between a Pt͑111͒ surface and layers of CH 3 Cl to understand the behavior of the photochemical cross section.…”

Dipole–dipole interactions among CH3Cl molecules on Ru(001): Correlation between work function change and thermal desorption studies

“…If we assume a coverage independent pre-exponential factor, v, E a (n) can be extracted by inverting a ⌬p-TPD peak profile. 13 The first order desorption rate is expressed as follows:…”

“…Previous efforts to predict the work function change upon monolayer completion ͓e.g., CH 3 Cl on Cu͑110͔͒, 13 from TPD analysis based on a single work function change measurement, 14 were unsuccessful. 13 The objectives of this work are twofold: ͑a͒ Correlate between the rate of desorption and the rate of work function change. Discrepancy between the two often originates from coverage dependence of the dipole moment.…”

Excitation and quenching mechanisms in the near-UV photodissociation of CH3Br and CH3Cl adsorbed on D2O or CH3OH on Cu(110)

“…22,23 There are several previous studies that have looked at the coadsorption systems of methyl halides with water, most particularly chloromethane and water. Due primarily to the electrostatic dipole moments of these species, the interactions between CH 3 Cl and D 2 O on metals are characterized by repulsion, and has been investigated by temperature programmed desorption (TPD) and modelling studies by Maschhoff et al 24 who concluded that the long range electrostatic dipole-dipole interactions are an important factor in the CH 3 Cl structures. The CH 3 Cl binding energies were found to decrease with increasing coverage of D 2 O and CH 3 Cl, and the repulsive interactions cause CH 3 Cl islands to form atop the preadsorbed D 2 O or between D 2 O islands.…”