ByMadhu Gyawali

Narayan AdhikariYadab Paudel

FTIR Measurements on November 06,08 at Reno

Nov 18, 08 PHYS 749UNIVERSITY OF NEVADA , RENO,NV

Introduction, Instrumentation:

Nov 18, 08

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)PHYS 749UNIVERSITY OF NEVADA , RENO,NV

http://en.wikipedia.org/wiki/Fourier_transform

Introduction…

Nov 18, 08 PHYS 749

Figures: From Lecturer’s Note (Pat Arnott)

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.

UNIVERSITY OF NEVADA , RENO,NV

Cloudy sky: window region high temperature (≈ 275 K, 7:28AM)

Clear sky: Lower temperature from deep surface (≈ 180K, 12:00AM)

Surface temperature ≈ 278-285K

Results: Temperature Vs. Wave number

Nov 18, 08 PHYS 749

UNIVERSITY OF NEVADA , RENO,NV

Results: Temperature Vs. Wave number

Nov 18, 08

Co2 peaks around wave number 670 cm-1

PHYS 749UNIVERSITY OF NEVADA , RENO,NV

Results: Temperature Vs. Wave number

Nov 18, 08 PHYS 749UNIVERSITY OF NEVADA , RENO,NV

Results: Radiance Vs. wave number

Nov 18, 08 PHYS 749UNIVERSITY OF NEVADA , RENO,NV

Results: Irradiance Vs. wave number (model)

Nov 18, 08 PHYS 749UNIVERSITY OF NEVADA , RENO,NV