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William M. Fairbank, Jr.
Professor
B.A., Pomona College, 1968; Ph.D., Stanford University, 1974;
Fellow, American Physical Society.
(970) 491-6660, fairbank@lamar.colostate.edu
Ultra Sensitive Analysis
Single Atom Detection
Single atoms are detected in our laboratory through the burst of
photons they absorb and emit as they pass through a dye laser beam
whose wavelength is in resonance with the atom. Recently we have
also detected photon bursts from single fast ions for the first
time. We are now developing a new radioisotope dating technique,
called Photon Burst Mass Spectroscopy (PBMS), capable of measuring
isotope ratios down to the 10-15 level.
A second method of single atom detection we have used is called
resonance ionization spectroscopy (RIS). We are working on a new
technique for ultrasensitive analysis of solid samples, called
SIRIS (Sputter-Initiated RIS). In SIRIS an ion beam vaporizes by
sputtering a microscopic portion of the sample. RIS is them used to
selectively count the atoms of a particular element in this region
of the sample.
Fundamental Physics
We have used the SIRIS method to look for atoms containing new
elementary particles which may exist around us at very low
concentrations but have so far escaped detection. A new SIMS
instrument with a microfocus ion gun will allow us to apply SIRIS
to the ultrasensitive analysis of semiconductor quantum wells,
solar cells and devices grown at Colorado State University and in
other laboratories. We are also collaborating with nuclear
physicists to use both RIS and laser fluorescence methods to study
short-lived nuclei created by accelerators.
Laser Spectroscopy
Our work in high-precision spectroscopy includes hyperfine
structure and isotope shift studies and absolute wavelength
measurements which test fundamental theories such as quantum
electrodynamics. We are also investigating a new effect we
discovered in resonance ionization with broadband lasers in which
odd-mass isotopes have a different response from even isotopes.
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