Mechanism of electron exchange between low energy He+ and solid surfaces

A general picture on the mechanism of electron exchange between low energy He⁺ ions and solid surfaces is proposed on the basis of experiments on three-dimensional angle resolving ion scattering spectroscopy in which not only He⁺ but neutral He is used as a projectile.     

Interface motion of capillary-driven flow in rectangular microchannel

In microchannel flow, gas-liquid interface behavior is important for developing a wide range of microfluidic applications, especially in passive microfluidic systems. This paper presents a discussion of interface motion driven by capillary action in a microchannel. We have extended the theory beyond the previous theory of capillary rise problem for a circular tube, to a rectangular microchannel. The same formula for the relation between nondimensional time and interface position is obtained as for a circular tube. We examined rectangular microchannels with several sizes (about 50 to 100 microm square) of glass capillaries and 85 x 68 microm and 75 x 45 microm polydimethylsiloxane (PDMS) microchannels fabricated by photolithography technique, respectively. We observed movement of the gas-liquid interface position and compared it to the dimensionless relation. We obtained the value of a dimensionless variable of driving force that is related to dynamic contact angles for glass-water, glass-ethanol, and PDMS-ethanol. Using this variable, interface motion can be predicted for any size of rectangular channels.     

Ultrasonic absorption of the oxyethylene group in aqueous nonelectrolyte solutions

The ultrasonic absorption from 6.5 to 220 MHz and velocities at 2.5 MHz have been measured in aqueous solution of triethylene glycol monobutyl ether as a function of concentration at 25°C. A single relaxational excess absorption, observed from 0.60 to 2.5 mol-dm^–3, is attributed to a perturbation of an equilibrium associated with solute-solvent interaction. Rate constants for the forward and reverse processes have been determined from the concentration dependence of the relaxation frequency, and the influence on the water structure by an addition of the solute has been considered. Solution densities were also measured in order to obtain the expansivity of the solution. The standard volume and enthalpy changes of the reaction have been estimated from the concentration dependence of the maximum excess absorption per wave length. A linear relationship between the number of oxyethylene groups and the free energy change between bonded water and nonbonded water is established.     

Structural relaxation of formic acid and its interaction with water and Xe at cryogenic temperatures

The glass-liquid transition of the amorphous HCOOH films and the reorganization of hydrogen-bonds of HCOOH during interactions with adsorbed D₂O and Xe have been investigated on the basis of temperature-programmed TOF-SIMS and TPD. On the as-deposited HCOOH film at 15 K, the physisorbed Xe atom permeates through pores and is trapped in the bulk during pore collapse upon heating. The hydrogen bonds of the HCOOH film are persistent up to 125 K as revealed from the interaction with the adsorbed D₂O molecules. The translational molecular diffusion commences at 125 K and dewetting of the HCOOH film follows at 150 K. The Xe atom incorporated in the bulk of the HCOOH film desorbs at 150 K concomitantly with dewetting of the film. These phenomena can be explained in terms of the glass-liquid transition of formic acid and the slow evolution of fluidity in the supercooled liquid phase.