Additional Participants

Post-doc

Robert Jackson
Jay LeGore

Graduate Student

Zhongyu Yang

Undergraduate Student

Wendy Kresge
Clifford Davis

Technician, Programmer

Nicholas LeCursi
Bronson Crothers
Conrad Silvestre
George Bernhardt

Research Experience for Undergraduates

Joel NgueMba

Project Period

September 1, 1999-August 31, 2003

Level of Access

Open-Access Report

Grant Number

9977800

Submission Date

1-9-2004

Abstract

This project, funded by the Major Research Instrumentation program, will develop a time-of-flight electron velocity analyzer using advanced modulation and Fourier deconvolution techniques with a throughput advantage on the order of 1000 over existing instruments. The new spectrometer will operate with ultra-high resolution in the energy range 1-1000 electron volts. It will be useful for the investigation of surface properties under ultra-high vacuum and a variety of other scientific and commercial applications. The device utilizes secondary chopping of the electron beam in the nanosecond or sub-nanosecond time regime, and state-of-the-art Fourier transform-based digital signal recovery methods. Additionally, there is potential for several orders of magnitude more throughput by using array detectors. Other substantial performance advantages arise when it is used with synchrotron sources. The ultimate result will be a new generation of spectrometers allowing a wide range of new applications, both applied and fundamental, to research, research training, and analytical work. This sophisticated instrumentation is of wide applicability to vibrational electron energy loss spectroscopy, e.g. high resolution electron energy loss spectroscopy (HREELS), higher energy spectroscopies (X-ray photoelectron (XPS), Auger electron (AES), and ultraviolet photoemission (UPS) spectroscopy), and gas phase ion (mass) spectrometry and gas phase photoemission. The new device allows a number of new experiments and analytical techniques. By reducing acquisition time from hours to seconds, surface reactions can be followed on a much faster time-scale, for example during thermal processing. The several orders of magnitude improvement in throughput has a dramatic affect on the sensitivity to low intensity processes, such as trace analysis in analytical surface chemistry applications, non-dipolar scattering in HREELS and inelastic diffraction. Broader applications include practical surface analysis of soft and rough materials, e.g. HREELS of polymers, as well as greatly improved analytical capabilities in more standard types of measurements, such as XPS. Development requires optimizing the design of charged particle beam chopping devices. The new instrument requires the adaptation of deconvolution software for optimum performance. In collaboration with several experienced private sector software companies, sophisticated numerical algorithms for signal recovery will be implemented. Development of the spectrometer includes extensive participation by faculty and students, involving both experimental and theoretical work.

A new time-of-flight electron spectrometer, developed with funding from the Major Research Instrumentation program, will be useful for the investigation of surface properties under ultra-high vacuum and a variety of other scientific and commercial applications. The scientific and engineering infrastructure at the University of Maine will be strengthened not only by the research enabled by this new instrument, but also by the education and career development of participants in the project, since students as well as faculty will be involved.

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