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Home Institutions and Research Projects of Recent REU Program Participants — 1999
The SRI REU program assigns each student to work with a staff professional on a
separate research project. Typically these projects are a sub-task on a larger research
program of the mentor. Some of these projects are independent with the mentor
overseeing the students progress on a daily basis. More than half of the projects
involve the student working in the laboratory side-by-side with a Ph.D. staff
member. Here the data collection task is more collaborative than independent. Since
the student projects are each individually supervised, the SRI program can
accommodate students with different starting and ending dates.
1999 REU Students & Program Directors
1999 REU Projects at SRI
Student from Pomona College
Mentor: Dr. Philip Cosby
Project:"Electron-Impact Dissociation of Neutral Molecules and
Radicals"
This project examines the dissociation products produced by
electron-impact dissociation
of neutral molecules and radicals. A fast beam of neutral molecules is
produced by
ionizing, mass selecting, and collimating a parent ion, then passing
the ion beam through
a charge transfer cell. The resulting neutral beam is crossed with an
electron beam to
produce dissociation fragments, which are collected by a time- and
position-sensitive
detector to determine absolute cross sections for the electron-impact
dissociation process
and product translational energy distributions.
Student from Cornell University
Mentors: Dr. Harald Oser and Dr. Michael Coggiola
Project:"Real-Time Detection of Chlorinated Aromatic Compounds
by REMPI-MS"
Chlorinated aromatic compounds, especially dioxin and furan species,
are extremely toxic
to humans, even at the level of one part per trillion. These types of
molecules are often
created in waste incinerators and metal plants. We are developing a
REMPI-based instrument
to detect these and other compounds in real-time, with a high degree
of sensitivity.
Supersonic-cooled, resonance enhanced multiphoton ionization
(Jet-REMPI) combined with
time-of-flight mass spectrometry (ToF-MS) provides the necessarily
high chemical
selectivity.
Student from Geogia Institute of
Technology
Mentors: Dr. Tom Slanger, Dr. Philip Cosby, and Dr. David
Huestis
Project:"The Contribution of Keck/Hires to Terrestrial
Nightglow Studies: Atomic/Molecular
Spectroscopy and Kinetics"
The unsurpassed resolution and sensitivity of the HIRES spectrograph
at the 10-m Keck I
telescope creates new opportunities for investigating the emissions of
the Earth's
atmosphere. Through collaborations between astronomers and aeronomers,
diagnostic
information about the terrestrial middle and upper atmosphere can be
attained. This
research is intended to provide a foundation for selecting and
interpreting new
measurements from the ground, from rockets and balloons, and from
space platforms. We need
a good model of terrestrial and extraterrestrial sources of emission
and absorption
features to take advantage of the improvements in optical
instruments. Because the real
atmosphere is variable on time scales of season, time-of day, or even
minutes, we need
schemes of calibrations that can be acquired with just a few
measurements. The overall
objective is to develop a comprehensive model of terrestrial nightglow
emissions with the
target of identifying and characterizing the nightglow emissions that
provide new
diagnostics for ionospheric processes.
Student from the New College of the
University of South Florida
Mentor: Dr. Gregory Faris
Project:"Photon Density Waves in Turbid Media"
The long-term goal of this project is to develop optical, noninvasive,
medical diagnostic
techniques. We use a measurement system comprising an
amplitude-modulated laser and
photomultiplier tube to measure the absorption and scattering
coefficients of tissue or
tissue phantoms. Tissue phantoms are made using Ropaque and blue food
dye (FD&C No.
1). Accurate measurement of tissue properties is possible by immersion
of a human hand in
the tissue phantom. Concentrations of chromophores of biological
interest can be derived
from measured absorption coefficients. We are extending this technique
to multiple
wavelengths for spectroscopy, using light emitting diodes (LEDs) as
light sources and
examining approaches for improving experimental accuracy.
Student from Valparaiso University
Mentors: Dr. Jeff Johnston and Dr. Laura Iraci
Project:"Uptake Coefficient Measurement of HNO3 on
Soot Aerosols"
Soot emissions from jet aircraft in the upper troposphere and lower
stratosphere may have
an impact on the generation/destruction of tropospheric and
stratospheric ozone. We are
interested in the reaction of HNO3 on soot aerosols, which
may have
implications for ozone levels in the stratosphere. HNO3 may
react on soot
surfaces to produce NOx (i.e., NO and NO2) and
H2O or
otherwise adsorb onto the soot surface, in effect, removing
HNO3 from the
stratosphere and thus producing less ozone depleting
NOx. This experiment is
designed to determine how HNO3 behaves on soot aerosols by
exposing HNO3
to soot aerosols in a flow tube reactor.
Student from the University of
Portland
Mentor: Dr. Gregory Faris
Project:"Development of Stimulated Scattering as a Diagnostic
for Supercritical Fluids"
The goal of this project is to develop techniques for monitoring
collective fluctuations
in the critical region and above, which will be suitable for studying
supercritical fuel
behavior. By overlapping a strong pump laser beam and a weaker probe
laser beam in a
sample, we can induce gain or loss on the probe beam. By scanning the
frequency of either
the pump or probe laser, we can perform spectroscopy on the resonant
scattering modes of a
sample. We use the fundamental wavelength of a Nd:YAG laser as a pump
beam with pulse
energies ranging from 50 microJoules to 1 milliJoule. A single-mode
tunable diode laser is
used as the probe laser, and stimulated Brillouin scattering and
Rayleigh scattering are
observed in supercritical hexane.
Student from the Unversity of
St. Thomas
Mentors: Dr. Laura Iraci and Dr. David Golden
Project:"Solubility of HOBr in Sulfuric Acid under
Stratospheric Conditions"
Halogen compounds are the dominant catalyst for the formation of the
polar ozone hole and
for global ozone loss in the upper stratosphere. Although bromine
concentrations are much
lower than chlorine concentrations and thus contribute to only a small
fraction of direct
ozone destruction, bromine compounds can indirectly enhance ozone loss
through coupling to
other radical families. One possible pathway for coupling the bromine
and chlorine
families is the reaction of HOBr with HCl in cold sulfuric acid
aerosols. As a first step
in this reaction, both gases must dissolve in the concentrated aerosol
droplets found in
the global stratosphere at approximately 10-12 km. The solubility of
HCl is well
understood, but HOBr has not been systematically
investigated. Experiments are in progress
to study the solubility of HOBr in a wide range of sulfuric acid
solution concentrations
and temperatures.
Student from Columbia University
Mentor: Dr. Richard Copeland
Project:"Pressure Dependence of the (3+1) REMPI Spectrum of
O2"
The absorption of solar ultraviolet (UV) radiation by the oxygen
molecule is the
starting point for many important chemical processes in the Earth's
atmosphere. A way to
examine the excited states of O2 responsible for the
single-photon UV
absorption and the nearby states that are optically forbidden in
single photon studies is
resonantly enhanced multi-photon ionization (REMPI) via a (3+1)
process. In this (3+1)
REMPI experiment, three 368-384 nm photons pump O2 to the
excited states, and
the fourth photon ionizes. The effects of pressure on the
E 3Su- ¬ X
3Sg-
(the longest band), the
f 1Su+(v = 3, 2,
1) ¬ X 3Sg-
and the D 3Su+(v
= 3, 2) ¬ X 3Sg-
bands of O2 are studied. Between 0.1 and 200 Torr, we find
that the relative
intensities of the bands vary unexpectedly with pressure. For example,
the relative
intensity of the longest band decreases at higher pressures, while the
relative intensity
of the D 3Su+(v
= 3, 2) ¬ X 3Sg-
band increases dramatically at higher pressures. The pressure
dependence is attributed to
collisional mixing with the previously unobserved one-photon
forbidden, three-photon
allowed 3Du
¬
X 3Sg- band.
Interested in participating? Check out the Application Form.
Contact Us:
For more information about SRI's REU Program, contact
Dr. Kostas Kalogerakis (650-859-3398) or
Dr. Gregory Faris (650-859-4131)
e-mail: reu@sri.com
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