Transcript Thesis DEFENSE

FTIR Measurements on November
06,08 at Reno
By
Madhu Gyawali
Narayan Adhikari
Yadab Paudel
Nov 18, 08
UNIVERSITY OF NEVADA , RENO,NV
PHYS
749
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
Nov 18, 08
UNIVERSITY OF NEVADA , RENO,NV
PHYS
749
Introduction…
IR Window 8-13 microns. IR radiation
from the Earth’s surface escapes to space
(cooling the Earth). Absorption by O3 near
9 microns ‘dirties’ the window.
Nov 18, 08
Figures: From Lecturer’s Note (Pat Arnott)
UNIVERSITY OF NEVADA , RENO,NV
PHYS
749
Results: Temperature Vs. Wave number
 Cloudy sky:
window region
high temperature
(≈ 275 K, 7:28AM)
 Clear sky: Lower
temperature
from deep
surface (≈ 180K,
12:00AM)
Surface
temperature ≈
278-285K
Nov 18, 08
UNIVERSITY OF NEVADA , RENO,NV
PHYS
749
Results: Temperature Vs. Wave number
Co2
peaks
around
wave
number
670 cm-1
Nov 18, 08
UNIVERSITY OF NEVADA , RENO,NV
PHYS
749
Results: Temperature Vs. Wave number
Nov 18, 08
UNIVERSITY OF NEVADA , RENO,NV
PHYS
749
Results: Radiance Vs. wave number
0.012
Rad(12:15)
Radiance
0.01
Rad(7:50)
0.008
Rad(7:28)
0.006
Rad(9:38)
0.004
0.002
0
500
700
900
1100
1300
1500
1700
1900
Wave Number(Cm-1)
Nov 18, 08
UNIVERSITY OF NEVADA , RENO,NV
PHYS
749
Results: Irradiance Vs. wave number (model)
Nov 18, 08
UNIVERSITY OF NEVADA , RENO,NV
PHYS
749