Lyn R. Watson

Evaluation of the Laser Ablation of Transition Metals/Metal Compounds by Time-of-Flight and Optical Spectroscopy

Abstract : A fast pulsed beam of neutral metal atoms is produced by laser vaporization of a solid metal or metal compound sample in a modified high- temperature mass spectrometer. Atomic beams of several eV kinetic energy are generated as measured using time-of-flight spectroscopy. The energy range can be controlled with the laser power, similar to studies conducted on thin metal films. The solid samples, however, overcome the problem of short sample lifetime associated with irradiating thin films. Samples have been irradiated for several hours without observing a change in beam intensity or energy, thus offering an interesting source for kinetic studies. Initial results of studies done on copper, nickel zinc and related oxide, sulfide, bromide, and chloride salts will be discussed as to their applicability to serve as a fast atom source. Spectroscopic data from these compounds will also be presented.... Laser ablation, Metals, Fast beams.

Trace Analysis Using Position-Sensitive Detection in Magnetic Sector Mass Spectrometry

Abstract A position-sensitive ion detection system for trace analysis with magnetic sector mass spectrometers is described in detail, with particular application to high temperature mass spectrometry. The detection system consists of two stacked microchannel plates (Chevron assembly) backed by a resistive anode encoder and associated electronics. The range of masses simultaneously detectable is m to 1.2m. For electron impact ionization of silver at an electron energy of 10.5 eV, the sensitivity is 1.6 × 10−7 Pa, and the mass resolution is 260 at mass 80 (valley 10% of the peak height definition). Additional applications for the detection system are discussed.