Werner F. Schmidt

Photoconductivity of nonpolar liquids induced by vacuum‐ultraviolet light

The intrinsic photoconductivity (pc) of 11 liquid hydrocarbons and silanes induced by VUV light was measured. From the onset of the pc the following thresholds were estimated in eV at T=(294±2) K: isopentane 9.15; n‐pentane 9.1; neohexane 8.75; 3‐methyl pentane 8.85; cyclohexane 8.75; n‐tridecane 9.25; n‐pentene‐1 8.33; cyclopentene 7.4; tetramethylethylene 6.8; hexamethyldisilane 6.75; triethylsilane 8.25. Absolute quantum yields were determines at 120 nm for a field strength of 2.5 kV cm−1.

Excess electrons and positive charge carriers in liquid ethane

Measurements of excess electron drift velocity as a function of the electric field were carried out up to field strengths of 280 kV/cm at temperatures from 111 to 216°K. Low field mobilities were obtained and at higher field strength the drift velocity increased more than proportionally with the field. The data are discussed on the basis of the trapping model, and thermally activated hopping is assumed for the motion. The jumping length as a function of the temperature was obtained from the high field data. The positive charge carrier seems to be of ionic nature and the mobility follows Waldens rule.

High- and low-mobility electrons in liquid neon

Abstract Electrons injected from the photocathode of a diode measurement cell into liquid neon produce two types of current signals. A fast rising and decaying signal in the time domain of several tens of nanoseconds which is attributed to the movement of delocalized electrons, and a current signal in the time domain of milliseconds which is attributed to the movement of localized electrons. The electron drift velocities in the delocalized and localized states were measured as a function of temperature and/or electric field strength. The results are discussed taking into account the energetics and dynamics of electron transport in simple condensed systems. A theoretical model of the kinetics of electron autolocalization is presented and compared to experiment.

On excess electron transport in liquid hydrocarbons

Abstract Electron drift velocities in liquid ethane, neopentane and neohexane were measured as a function of the electric field strength up to values of 240 kV cm −1 , 150 kV cm −1 and 140 kV cm −1 , respectively. In neopentane the drift velocity increases less than proportional to the electric field above 5 kV cm −1 indicating the influence of quasi-free electron conduction between shallow traps. In ethane the drift velocity increases more than proportional with field above 80 kV cm −1 . The motion is trap controlled and the electric field is thought to increase the jump frequency. In neohexane the drift velocity remained proportional to the electric field up to 140 kV cm −1 .

Excess electrons in liquid hydrogen, liquid neon, and liquid helium

Abstract The drift velocity of photo injected electrons in liquid hydrogen, liquid neon and liquid helium was measured at several temperatures as a function of the electric field strength up to 100 kV/cm. The magnitude of the drift mobilities and the field and temperature dependencies obtained from these measurements confirm the model of electron localization in bubbles. In liquid neon in addition a fast electron signal was observed which is attributed to electron migration in the delocalized state.

Electron transport in mixtures of liquid methane and ethane

The mobility of excess electrons in liquid mixtures of methane and ethane was measured over the entire range of composition at T=111 °K. Field dependent mobilities were observed at higher field strengths. The data are discussed on the basis of the quasifree and localized electron models.

MOBILITY OF EXCESS ELECTRONS IN LIQUID METHANE.

Abstract The drift velocity of excess electrons in liquid methane was measured for electric fields from 75 to 15 000 V cm−1. At lower field strengths the drift velocity increases proportional to the electric field and yields a mobility of (450 ± 50) cm2 V−1 sec−1. Above 1500 V cm−1 the drift velocity varies with E1/2.

Dissociative electron attachment to H2O2: a very effective source for OH and OH− generation

Abstract Dissociative electron attachment (DEA) to hydrogen peroxide (H 2 O 2 ) is studied by two independent electron beam experiments using mass spectrometric detection of the product ions. The fragments OH − and O − are observed from a prominent low energy resonance peaking near 0.4 eV. The partial absolute DEA cross-sections are 6.8×10 −17 and 1.7×10 −17 cm 2 for the OH − and the O − channels, respectively. These numbers are several orders of magnitude higher than for the corresponding DEA processes in simple OH containing organic compounds. These numbers are also important from the point of view of radiation damage in biological tissues.

Ionic mobilities in liquid xenon

The drift mobility of positive ions of tetramethylsilane (TMSi) and of negative oxygen ions in liquid xenon was measured as a function of temperature from 161 K (triple point) to 205 K. The mobility of the TMSi/sup +/ ion is more than one order of magnitude lower than the intrinsic mobility of positive charge carriers (holes) in very pure liquid xenon. The positive ionic mobility is influenced by electrostrictive effects, which lead to the formation of solid layers of Xe atoms around the ion, and to a locally enhanced viscosity. A simple model for the cluster formation is discussed. Qualitative agreement is obtained over most of the temperature range, but serious deviations occur at the triple point. Another shortcoming of the model is the fact that it cannot explain the higher mobility of the negative oxygen ions. >

Optical Spectral Change in Conducting Polymer Due to Insulator-Metal Transition Induced by Light Irradiation and Proposal As Optical Memory Element

By the irradiation of light on the conducting polymer like polythiophene doped with diaryliodonium salts, its absorption spectrum changes remarkably, which can be explained in terms of an insulator-metal transition due to light induced doping. The application of this phenomenon as an optical memory element which can be written by the light irradiation, is proposed.