R.E. Ballard

Photoelectron spectroscopy of liquids: relationships between ionization energy and reduction potential

Abstract The standard (reduction) potential of a half-cell, E, and the photoelectric work function, W (ev), are related by W = E + 4.4. Empirical relationships between the gas-phase ionization energy and polarographic half-wave potentials are given a theoretical basis.

New apparatus for liquid sampling in electron spectroscopy: He(I) spectra of the vapours and surfaces of methanol, ethanol, 1-heptanol and 1-decanol

Abstract A new apparatus is described for maintaining either a flowing or a stationary liquid surface within an evacuated compartment for the purposes of electron spectroscopy, mass spectroscopy, etc. The liquid is made to flow down a tungsten rod which can be cooled or heated by a saturated slush bath or liquid. The position of the rod is variable so that the liquid surface can be held in the best position and orientation. By varying the rate of flow or by completely stopping the flow of liquid it is possible to examine surfaces at different times after formation and to carry out kinetic studies. The He(I) photoelectron spectra are reported of flowing surfaces of methanol and ethanol at −78°C and also of the vapours above the flow. Spectra of 1-heptanol at 0°C and 1-decanol at 20°C are also given. Contamination of these liquid surfaces with loss of spectral structure occurs in the spectrometer within 30 s to 2 min of formation.

The He(I) photoelectron spectrum of benzyl alcohol-liquid surface and gas phase

Abstract He(I) photoelectron spectra of benzyl alcohol (liquid surface and gas phase) are presented and a simple method is given for the removal of the effects of He(Iβ) impurity. In addition to the general shift to lower ionisation energy usually observed in the spectrum of neutral (uncharged, as opposed to ionic) substances on change of phase from gas to liquid, there are also shifts in the ionisation energies of some bands relative to others: specifically the non-bonding O band shifts on liquefaction by O.5 eV more than the other bands. This relative shift is attributed to hydrogen bonding.

The surface concentrations of binary liquid mixtures measured by UV photoelectron spectroscopy

Abstract By means of He(I) photoelectron spectroscopy the surface concentrations of liquid mixtures of n -decan-1-ol. 1,2-ethanediol, tris(dioxa-3,6-heptyl)amine and hydroxypropionitrile have been determined at ambient temperatures. Measurements of the surface tensions of these mixtures have been made and qualitative agreement is found between the surface compositions and those predicted by the Gibbs adsorption formula.

He(I) photoelectron studies of liquids and gases

Abstract He(I)photoelectron spectra of tetramethyl- p -phenylenediamine, phenol, benzyl alcohol and formamide in gaseous and liquid forms have been measured. The structure underlying these spectra is enhanced by plotting them in the form of their second derivatives. Comparison of the spectra of the gas phase and liquid surface reveals the effects of intermolecular interaction and sometimes enables the determination of the molecular form of the surface layer.

The electron affinity of water and the structure of the hydrated electron

Abstract The electron affinity of water has been obtained by a new method and a value of 1.3 eV is proposed. This value is consistent with an ice-like structure for the hydrated electron in which four water molecules are disposed about a central water anion, there being small (≈ 10°) changes from the ice structure values of the angles between the dipole moments.

Surface activity of solutes in hydroxypropionitrile studied by He(I) photoelectron spectroscopy - EGG lecithin, sodium oleate, malachite green and tris-(dioxa-3,6-heptyl)amine

Abstract We have used He(I) photoelectron spectroscopy to measure the percent surface coverage for substances dissolved in hydroxypropionitrile, HO(CH 2 ) 2 CN. The concentration at which 100% surface coverage is achieved, C 100 , is an inverse measure of surface activity. Measured values of log 10 ( C 100 ), with C 100 in molarity units, in hydroxypropionitrile at 20°C are (in order of diminishing surface activity): −3.85 (egg lecithin), −2.85 (sodium oleate), −0.64 (malachite green hydroxide), and 0.34 [tris(dioxa-3,6-heptyl)amine].

The He(I) photoelectron spectra of lipid phosphatides

Abstract Complete layers of some lipids are formed spontaneously on the surfaces of solutions of sufficient concentration in certain solvents, e.g. phosphatidylcholine (egg lecithin) and phosphatidylinositol (wheat germ) dissolved in hydroxypropionitrile. The He(I) photoelectron spectra of phosphatides in such layers contain: (1) a broad band, assigned to alkyl groups, with maximum intensity at about 11 eV, (2) another broad band at about 8 eV, assigned to the PO - 4 group with about 1 % of the band area of (1).

Auger and electron energy loss studies on liquid surfaces

Abstract The effects of surfactant layers on the Auger and electron energy loss spectra of liquid formamide and hydroxypropionitrile are reported. The characteristic structure of formamide remains in the loss spectrum even when there is complete surface coverage as verified by the Auger spectra.

He(I) photoelectron studies of lipid layers

Abstract It is shown how films of pure or mixed lipids can be investigated by means ofHe(I) photoelectron spectroscopy; the relationship between the results and those from pressure/area studies is discussed. Films of phosphatidylcholine (egg lecithin), cholesterol and mixtures of the two have been studied; a monolayer of lecithin facilitates the early stages of the surface adsorption of cholesterol but a monolayer of cholesterol has the reverse effect on lecithin.