2. Pump system using liquid nitrogen as a coolant, e.g., a Linkam
stage (Linkam Scientific Instruments), connected to a liquid
nitrogen dewar (1 L minimum) and the sample holder
described above (see Note 5).
3. Datalogging thermometer with type T thermocouple (e.g.
Fluke) and stopwatch.
4. Two CaF 2 windows, 25 Â 2 mm (e.g., from Korth Kristalle,
Kiel, Germany), and a Teflon spacer 25 Â 0.25 mm (e.g., from
Harrick Scientific).
3 Methods
3.1 Setting Up
and Background
Spectrum Acquisition
1. Turn on the FTIR purge gas generator (pressure of ~50 psi).
Make sure all compartment areas of the FTIR system are
connected to the purge system and dry air is supplied in the
sample area (see Note 6).
2. Dependent on the available setup, either a TGS or an MCT
detector can be used (see Note 1):
(a) When an MCT detector is used, cool it with liquid nitrogen (LN 2 ): slowly add LN 2 in small portions using a
funnel. The detector is properly cooled when the energy
level of the background spectrum reaches its maximum
and remains stable. Make sure to refill the detector in time
with LN 2 , which typically should be done after about
4–8 h.
(b) Alternatively, a TGS detector can be used, which does not
need to be cooled.
3. In case the temperature-controlled transmission sample holder
is used, clean two CaF 2 windows with 70% ethanol and mount
them in the sample holder. Insert a Teflon spacer between the
two windows to avoid fringing (see Note 7). Place the sample
holder in the FTIR, close the lid around the sample holder area,
and wait about 5–10 min until the sample area is thoroughly
flushed with dry air from the purge system (see Note 8). In case
the ATR accessory is used, clean the diamond/ZnSe crystal
with 70% ethanol.
4. Open the program for acquisition of FTIR spectra. Set the
instrumental settings in the program: (1) give a background
name (yymmdd-bckg); (2) add scan settings including type of
scan (“background”), spectral region (4000–900 cm
À1 ), and
number of scans (8); (3) set spectrometer resolution (4 cm
À1 )
and deselect/select the automatic CO 2 /H 2 O correction (see
Note 9); (4) select the type of accessory that is used, transmission mode in case of the temperature-controlled sample holder
334
Willem F. Wolkers and Harrie ¨ tte Oldenhof
stage (Linkam Scientific Instruments), connected to a liquid
nitrogen dewar (1 L minimum) and the sample holder
described above (see Note 5).
3. Datalogging thermometer with type T thermocouple (e.g.
Fluke) and stopwatch.
4. Two CaF 2 windows, 25 Â 2 mm (e.g., from Korth Kristalle,
Kiel, Germany), and a Teflon spacer 25 Â 0.25 mm (e.g., from
Harrick Scientific).
3 Methods
3.1 Setting Up
and Background
Spectrum Acquisition
1. Turn on the FTIR purge gas generator (pressure of ~50 psi).
Make sure all compartment areas of the FTIR system are
connected to the purge system and dry air is supplied in the
sample area (see Note 6).
2. Dependent on the available setup, either a TGS or an MCT
detector can be used (see Note 1):
(a) When an MCT detector is used, cool it with liquid nitrogen (LN 2 ): slowly add LN 2 in small portions using a
funnel. The detector is properly cooled when the energy
level of the background spectrum reaches its maximum
and remains stable. Make sure to refill the detector in time
with LN 2 , which typically should be done after about
4–8 h.
(b) Alternatively, a TGS detector can be used, which does not
need to be cooled.
3. In case the temperature-controlled transmission sample holder
is used, clean two CaF 2 windows with 70% ethanol and mount
them in the sample holder. Insert a Teflon spacer between the
two windows to avoid fringing (see Note 7). Place the sample
holder in the FTIR, close the lid around the sample holder area,
and wait about 5–10 min until the sample area is thoroughly
flushed with dry air from the purge system (see Note 8). In case
the ATR accessory is used, clean the diamond/ZnSe crystal
with 70% ethanol.
4. Open the program for acquisition of FTIR spectra. Set the
instrumental settings in the program: (1) give a background
name (yymmdd-bckg); (2) add scan settings including type of
scan (“background”), spectral region (4000–900 cm
À1 ), and
number of scans (8); (3) set spectrometer resolution (4 cm
À1 )
and deselect/select the automatic CO 2 /H 2 O correction (see
Note 9); (4) select the type of accessory that is used, transmission mode in case of the temperature-controlled sample holder
334
Willem F. Wolkers and Harrie ¨ tte Oldenhof