Ion-molecule reactions and ion energies in a CF4 discharge

Absolute cross sections have been measured for reactants typically found in carbon tetrafluoride (CF(4)) discharges for collision energies below a few hundred electron volts. The reactions investigated include collision-induced dissociation and dissociative electron transfer reactions for CF(+)(3) and F(+) colliding with CF(4), and collisional electron detachment for F(-) colliding with CF4. Also presented are measurements of energies and relative intensities of ions generated in dc Townsend CF4 discharges with E/N values ranging from 4 x 10(-18) V m(2) to 25 x 10(-18) V m(2) [4 to 25 kTd]. Ion energy and ion intensity data for the Townsend discharges are analyzed in light of the measured cross sections.

Studies of Ion Kinetic-Energy Distributions in the Gaseous Electronics Conference RF Reference Cell

A review is presented of kinetic-energy distribution measurements for ions striking grounded surfaces in a Gaseous Electronics Conference (GEC) rf Reference Cell. Two experimental arrangements that have been used to measure ion energies in the GEC Cell are described, and a comparison of their performance under different operating conditions is presented. Significant results from ion-energy analysis in the Reference Cell are highlighted, including evidence of effects due to surface conditions on ion sampling, verification of electrical behavior of the cell, inferences about ion-molecule reactions indicated by the shapes of measured ion kinetic-energy distributions (IEDs), and the use of measured IEDs for the validation of theoretical models. The paper concludes with a detailed study of IEDs measured for rf plasmas generated in mixtures of argon and oxygen, using both experimental arrangements.

The Gaseous Electronics Conference RF Reference Cell-An Introduction

This paper provides an introduction to the Gaseous Electronics Conference (GEC) RF Reference Cell, and to the articles published in this Special Issue of the Journal of Research of the National Institute of Standards and Technology. A brief summary of the history and purpose of the Reference Cell concept is presented, and recent changes to the GEC Cell design are documented. The paper concludes with highlights of research performed on GEC Cells, and with an appendix of all known publications that present research performed on GEC Cells.

Absolute Spatially- and Temporally-Resolved Optical Emission Measurements of rf Glow Discharges in Argon

Spatially- and temporally-resolved measurements of optical emission intensities are presented from rf discharges in argon over a wide range of pressures (6.7 to 133 Pa) and applied rf voltages (75 to 200 V). Results of measurements of emission intensities are presented for both an atomic transition (Ar I, 750.4 nm) and an ionic transition (Ar II, 434.8 nm). The absolute scale of these optical emissions has been determined by comparison with the optical emission from a calibrated standard lamp. All measurements were made in a well-defined rf reactor. They provide detailed characterization of local time-resolved plasma conditions suitable for the comparison with results from other experiments and theoretical models. These measurements represent a new level of detail in diagnostic measurements of rf plasmas, and provide insight into the electron transport properties of rf discharges.

Desorption of ions from rat membranes: selectivity of different ionization techniques

Complex lipid biomarkers, including phosphatidylcholines, cerebrosides and sulfatides, are shown to be desorbed intact from rat brain myelin and rat liver microsomes by liquid secondary ion mass spectrometry, by plasma desorption and by laser desorption. Different polar lipids are favored by the different desorption techniques and as negative or positive ions. These selectivities support current theories about ionization for the different techniques.

Mass spectral analysis of complex lipids desorbed directly from lyophilized membranes and cells

Three desorption ionization techniques--laser desorption, plasma desorption and fast atom bombardment mass spectrometry--have been applied to lyophilized cells, membranes, lysed cells and various extracts. It has been shown that intact polar lipids are selectively desorbed from biological membranes by these methods and that their mass spectra provide "fingerprints" which reflect the unique biochemical composition of each class of cell or membrane.