Madhu Gyawali

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FTIR Measurements on November 06,08 at Reno

• By
• Madhu Gyawali
• Narayan Adhikari
• Yadab Paudel

PHYS 749
UNIVERSITY OF NEVADA , RENO,NV
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Introduction, Instrumentation

• FTIR is an optical instrument used to measure
  properties of light over a specific portion of
  the electromagnetic spectrum, 5 microns to 20
  microns.
• FTIR collects infrared spectra by an
  interferogram of a sample signal using an
  interferometer, then performs a Fourier Transform
  on the interferogram to obtain the spectrum.
• An interferometer is an instrument that uses the
  technique of superimposing (interfering) two or
  more waves, to detect differences between them.
  The FTIR spectrometer uses a Michelson
  interferometer.
• (Source-Pat Arnott,ATMS 749)

http//en.wikipedia.org/wiki/Fourier_transform
PHYS 749
UNIVERSITY OF NEVADA , RENO,NV
3
Introduction
IR Window 8-13 microns. IR radiation from the
Earths surface escapes to space (cooling the
Earth). Absorption by O3 near 9 microns dirties
the window.
Figures From Lecturers Note (Pat Arnott)
UNIVERSITY OF NEVADA , RENO,NV
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Results Temperature Vs. Wave number

• Cloudy sky window region high temperature ( 275
  K, 728AM)
• Clear sky Lower temperature from deep surface (
  180K, 1200AM)
• Surface temperature 278-285K

PHYS 749
UNIVERSITY OF NEVADA , RENO,NV
5
Results Temperature Vs. Wave number

• Co2 peaks around wave number 670 cm-1

PHYS 749
UNIVERSITY OF NEVADA , RENO,NV
6
Results Temperature Vs. Wave number
PHYS 749
UNIVERSITY OF NEVADA , RENO,NV
7
Results Radiance Vs. wave number
PHYS 749
UNIVERSITY OF NEVADA , RENO,NV
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Results Irradiance Vs. wave number (model)
PHYS 749
UNIVERSITY OF NEVADA , RENO,NV