Laboration thermal FTIR, Responsible: Johan Mellqvist ([email protected]) Equipment : FTIR spectrometer, computer, calibration cell (bucket), liquid ammonia, source, heat source (max 110 V), heat gun, temperature sensor , calibration spectrum in absorbance of ammonia (100 ppmm at RTP). Absorbance is defined as -log10(I/Io). Deadline 1 week after excercise. Procedure: 1. Get familiar with IR spectrometer and equipment To start measurements run OPUS, password "OPUS" Run measurements, "sample single channel" 2. Fill liquid nitrogen in spectrometer 3. Fill calibration cell with ammonia (together with supervisor)

4. Calibrate the instrumnets at two different temperatures : 300 and 330 K Use explorer, http: 10.10.0.1 direct command: FLM=1    blackbody measurement  FLM=0, Outside measurement     set blackbody to T BTS=0  BTS= T, forinstance "BTS=330" (330 K)   till  330  BTS=0, turn blackbody off.     Get black body temperatur:  GBT  

From these calibrations you can compare the blackbody curve, with the FTIR to correct for the instrument response. (Can be done this at home)

5. Measure spectra with and without calibration cell of : a) hot light source, 50 V b) sky c) Someones bare stomach d) cold brickwall e) hot brickwall. (use heatgun) f) Aluminum plate For every measurement use also the optical temperature probe to measure directly the baclground temperature.

6. ) Convert the spectra to ascii files, and send them via mail. 7. At home, (work 2 and 2) a) Import the spectra into matlab or excel and plot them. b) compare theoretical blackbody curves (in wavenumber) , with the one measured by the FTIR to correct for the instrument response c) analyse the temperature of the background using Eq. 2 and 1. d) analyse the amount of ammonia in the calibration cell for the different measurement cases using the forward model, Eq. 1 . 8. Write a lab report 1.Experimental setup . Figure of av experimetal setup and description of the components and their function (ligh source, detector, FTIR). . 2. Methodology. 3. Result:Plot spewctra and ammonia in each case. 4. Discussion.

Forward model,

I obs (ν ) = (1 − τ 1 ) B1 + τ 1[(1 − τ 2 ) B2 + τ 2 B3 ]

Eq. 1

τ i (ν , p, T ) = transmittance = e −σ (ν , p ,T , f ,)⋅c⋅x Bi (ν , T , f ) = radiance of blackbody at T The B distribution (in cm-1) represent the spectral radiance of blackbodies—the power emitted from the emitting surface, per unit projected area of emitting surface, per unit solid angle, per spectral unit (frequency, wavelength, wavenumber or their angular equivalents) B(ν,T) = c1ν3 / (e c2 ν / T - 1)

Eq. 1

where B(ν,T) has units of W/(m2∗ster∗cm-1) and c1 = 2hc2 = 1.191044 x 10-8 W/(m2∗ster∗cm-4) and c2 = hc/k = 1.438769 K∗cm

Wiens displacement law: νmax = 1.95∗T (cm-1)

Eq. 2