High-Performance Fourier Transform Infrared Spectrometer:

1
High-Performance Fourier Transform Infrared
Spectrometer A Versatile Modular
Interdisciplinary Instrument in the Regional
Atmospheric Profiling Center for
Discovery David A. Bowdle University of
Alabama in Huntsville NASA/UAH Atmospheric
Science "Brown Bag" Seminar December 4, 2002
2
AmOR
OUTLINE

• FTIR Theory
• FTIR Instrument
• Optical Layout
• Basic Capabilities
• FTIR Science
• Planned Use in RAPCD
• Potential Interdisciplinary Projects
• Brain-storming

3
AmOR
FTIR THEORY
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.
4
NICOLET NEXUS 870 FTIR EXTERNAL VIEW
Interferometer Compartment
External Experiment Data Interface
Dual Source Compartment
Dual Detector Compartment
Main Sample Compartment
Left External Beam Port
AmOR
5
NICOLET NEXUS 870 FTIR INTERNAL VIEW
Michelson Interferometer)
Power Supply Signal Processor
Data Purge Ports
DTGS Detector (MIR)
Internal Source Compartment
InGaAs Detector (NIR)
Main Sample Compartment (KBr Windows)
Motorized Path Selection Mirrors
AmOR
6
NICOLET NEXUS 870 FTIR TOP VIEW
Motorized Collimating Mirror
HeNe Laser
Michelson Interferometer)
Motorized Aperture Wheel
Condensing Mirror (Sample)
Condensing Mirror (Source)
Incandescent Source (VIS/NIR)
Globar Source (MIR)
AmOR
7
NICOLET NEXUS 870 FTIR OPTICAL PATH
External Source Beam
Left External Beam
Left External Beam
AmOR
8
NICOLET NEXUS 870 FTIR INTERFEROMETER
Piezo-Electric Dynamic Alignment
HeNe Laser
Fixed Mirror
Laser Pickoff Mirror
KBr Beam Splitter Extended Range
Moving Mirror Drive
Dynamic Alignment Phase Detectors
AmOR
9
AmOR
NICOLET FTIR CAPABILITIES

• 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 (ms) processes
• Phase modulation
• Dithering of fixed mirror
• Analysis of thin layers

10
AmOR
FTIR OPERATION
Attend demonstration of Nicolet Nexus 870 FTIR in
NSSTC Room 2014 after presentation and
brainstorming session
11
NICOLET NEXUS FTIR - REMOTE SENSING STATION
HEPA Filters
Solar Tracker Chimney
Dimming Incandescents
Horizon Scanner Chimney
Utility Buss Bar 110, 208 1/Ph, 2083/Ph Air,
Vacuum, Nitrogen Data Ports, Light Switch
Optical Curtains
Optical Bench
Cooling Water Drain
Not Shown Dimming Fluorescents Casework
AmOR
12
AEROSOL mICROPHYSICS AND RADIOMETRY LAB
AmOR
13
AEROSOL mICROPHYSICS AND RADIOMETRY LAB
AmOR
14
RAPCD CHIMNEY INSPECTION
Jay Leko interviews for a RAPCD research position
Mike Newchurch goes to great lengths to make sure
RAPCD works
AmOR
15
AmOR
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

16
AmOR
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

17
AmOR
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

18
AmOR
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