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High-Performance Fourier Transform Infrared Spectrometer:
A Versatile Modular Interdisciplinary Instrument
in the Regional Atmospheric Profiling Center for Discovery
David A. BowdleUniversity of Alabama in Huntsville
NASA/UAH Atmospheric Science "Brown Bag" SeminarDecember 4, 2002
• FTIR Theory
• FTIR Instrument
Optical Layout
Basic Capabilities
• FTIR Science
Planned Use in RAPCD
Potential Interdisciplinary Projects
Brain-storming
OUTLINE AOR
FTIR THEORY AOR
Let spectrum 1 represent a gas sample or a suspended aerosol in the atmosphere or in a laboratory chamber, or an aerosol deposit on
a substrate. Let spectrum 0 represent a blank.
0
1
000
111
0
1
00
11
0
1
0
1
T
T
tG
tG
A
A
L
L
N
N
Photo-counts
SourceRadiance
Receiver Areaand Solid Angle
OpticalEfficiency
Gain, Spectral Resolution,
Intergration TimeTransmission
1,0
0
1
0
1 lnln KT
T
N
NAU
Extinction
UnitsInstrumentArtifacts
01,1
2
1311 OmLkg
mk
m
gCAU nonlinear
ConcentrationIn situ MassExtinctionEfficiency
OpticalDistortion
EffectiveLength
CorrectionReduce
By Design
NICOLET NEXUS 870 FTIR – EXTERNAL VIEW
External Experiment
Data Interface
Left External Beam Port
Dual Detector Compartment Main Sample
Compartment
Dual Source Compartment
Interferometer Compartment
AOR
NICOLET NEXUS 870 FTIR – INTERNAL VIEW
Main SampleCompartment
(KBr Windows)
DTGSDetector
(MIR)
InGaAsDetector
(NIR)
Motorized Path Selection Mirrors
Data & Purge Ports
Power SupplySignal Processor
Michelson Interferometer)
InternalSource
Compartment
AOR
NICOLET NEXUS 870 FTIR – TOP VIEW
Incandescent Source(VIS/NIR)
Globar Source(MIR)
CondensingMirror
(Source)
MotorizedAperture
Wheel
CondensingMirror
(Sample)
MotorizedCollimating
Mirror
Michelson Interferometer)
HeNe Laser
AOR
LeftExternal
Beam
ExternalSourceBeam
NICOLET NEXUS 870 FTIR – OPTICAL PATH
LeftExternal
Beam
AOR
NICOLET NEXUS 870 FTIR – INTERFEROMETER
HeNe Laser
Moving Mirror Drive
Piezo-Electric Dynamic Alignment
FixedMirror
LaserPickoffMirror
Dynamic Alignment Phase Detectors
KBr Beam Splitter
Extended Range
AOR
NICOLET FTIR CAPABILITIES AOR
Linear scan Scan speeds up to ~50 Hz
Spectral resolution as fine as ~0.125 cm-1
Spectral range from 375-11,000 cm-1
Automated experiment setup including alignment; recognition of key components and accessories; selection of source, detector, and sample chamber; diagnostics; etc.
Easily adaptable to custom attachments
Step scan Amplitude modulation
• Chopper, with lock-in-amplifier• Repeatable sample phenomena
• Slow (ms) to ultra-fast (s) processes Phase modulation
• Dithering of fixed mirror•Analysis of thin layers
FTIR OPERATION AOR
Attend demonstration
of Nicolet Nexus 870 FTIR
in NSSTC Room 2014
after presentation and
brainstorming session
NICOLET NEXUS FTIR - REMOTE SENSING STATION
AOR
Solar TrackerChimney
Horizon ScannerChimney
OpticalCurtainsOptical
Bench
CoolingWater
& Drain
Utility Buss Bar110, 208 1/Ph, 2083/PhAir, Vacuum, Nitrogen
Data Ports, Light Switch
DimmingIncandescents
Not Shown:Dimming Fluorescents
Casework
HEPAFilters
AEROSOL ICROPHYSICS AND RADIOMETRY LAB
AOR
AEROSOL ICROPHYSICS AND RADIOMETRY LAB
AOR
RAPCD CHIMNEY INSPECTION
Mike Newchurchgoes to great lengths
to make sure RAPCD works
Jay Lekointerviews for
a RAPCD research position
AOR
PLANNED USE IN RAPCD
Composition and Concentration of Particles and Trace Gases
Atmospheric Chemistry Measurements
Column optical depth, using multi-spectral Langley plots from a roof-mounted solar tracker with dithered pointing
Horizontal optical thickness, using one-way or two-way transmission with a roof-mounted alt-azimuth scanner
Cloud initiation, cloud particle phase, fog chemistry
Aspirated sample analysis, using bottles, filters, impactors
Size-dependent composition of airborne mineral dust
Deployment in RAPCD mobile van
AOR
PLANNED USE IN RAPCD
Composition and Concentration of Particles and Trace Gases
Atmospheric Chemistry Simulations
Artificial aerosols suspended in air, deposited on substrates
Heterogeneous chemical reactions, chemical kinetics
Calibration/Validation of Atmospheric Sensors and Models
Backscatter enhancement spectra from particle coatings
Composition of calibration particles for lidar backscatter
Optical distortion in particulate deposits on substrates
Scattering from non-spherical particles (e.g., pollen grains)
Polarimetry in transmission, forward scatter, backscatter
AOR
INTERDISCIPLINARY PROJECTS
Satellite remote sensing validation
Precipitation chemistry (remote or aspirated)
Spectral backscatter from simulated river surfaces
Optical emissions and chemical byproducts of lightning
Spectroscopy of simulated interstellar dust grains
Solar spectroscopy and solar variability
Nano-technology, bioaerosol detection
Brief brain-storming session after seminar dismisses
AOR
SUMMARY AND CONCLUSIONS
New high-performance FTIR obtained for RAPCD
Provides versatile tool for atmospheric chemistry research, in both ambient and simulated environments
Initial installation in RAPCD aerosol lab expected in January. Rooftop scanners to be acquired in future proposals.
Offers opportunity for interdisciplinary research ventures by adding modular commercial or in-house accessories
AOR
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