Progress in water vapour spectroscopy at RAL. Dr Robert McPheat CAVIAR Progress Meeting UCL, 13/05/2010. Measurements in the mid- and near-IR. These measurements were intended to target the weak water vapour continuum. Long path lengths.
Progress in water vapour spectroscopy at RAL
Dr Robert McPheat
CAVIAR Progress Meeting
Measurements in the mid- and near-IR.
These measurements were intended to target the weak water vapour continuum.
Long path lengths.
Measurements carried out at moderate (0.01cm-1) & high resolution (0.002cm-1) using the Bruker IFS125 HR FTS.
Initial measurements revealed a need for better line data too.
High resolution measurements 0.002 cm-1 using the Bruker IFS120/5 HR
Long integration times (~ 12 hours) in mid-IR
High temperature pressure gauge & filling line
Temperature & pressure logging
Outer vacuum jacket
Transfer optics vacuum tank
Example Spectra at 160 °C
3000 hPa Water vapour
1600Wavenumber / cm-1 12000
Self Broadened Spectra
3000 hPa Water vapour at 160 °C
2000Wavenumber / cm-1 11000
Air Broadened Spectra
600 mbar water vapour in 5 bar total pressure mixture with air at 160 deg. C
2500Wavenumber / cm-1 10000
SPAC measurement procedure
Pure H2O measurements (self-continuum):
1) empty cell
2) Argon (same pressure as H2O in step 3)
3) pure H2O (same pressure as in step 2)
4) Argon (same pressure as H2O in step 3)
5) empty cell (quick measurement)
H2O + Air measurements (foreign-continuum):
1) empty cell
2) Air (5 atm)
3) Air + H2O (5 atm total)
4) Same as in 2)
5) empty cell
2000 – 10000 cm-1, 5 – 1 µm
8500 – 14000 cm-1, 1.18 – 0.714 µm
FForeign (H2O + Air; 5atm total pressure) measurements, in addition to the pure H2O
(F) Only foreign (5 atm total pressure) measurement
Plan for mid-IR
800 – 2100 cm-1, 12.5 – 4.8 µm
| SPAC, 20m | LPAC, 512m
(F) Only foreign measurement: H2O + Air(1.5atm)
F Foreign measurement: H2O + Air(1.5atm), in addition to the pure one