Readme for Spectra of Thin Films with Varying Exposure
Time
For further details please see Fraser et al., A&A, 2003.
Format
The spectra are in ASCII format as *******.dat files. The left hand column reads
frequency in wavenumbers (cm-1) and the right hand column is the absorbance. The
data is tab-separated:
X-column
cm-1
Y-column
Absorbance
File Name Format
Files were named according to the experiment conducted:
experiment_exposuretime_temperature.dat
Pure Ices (Control Experiments):
Named: CO_10sec_15K.dat
CO
;
‘Layered’ Ices:;
a)
Named: a) COunderX_20sec_15K.dat
b) COoverX_60sec_15K.dat
X
b)
CO
CO
Exposure Times and Ice Thickness
Ice System
Cumulative Exposure Time When Spectrum
Taken (s)
CO
10, 20, 30, 60 , 90, 120
X
CO-X (1:1)
120
CO-CH4: 120
CO-CO2: 240
CO-CH3OH: 900
CO under X CO: 120, CH4: 120
CO: 240, CH3OH: 240
CO: 240, CO2: 240
CH4: 120, CO: 10, 20, 30, 60, 90, 120
CO over X
CH3OH: 240, CO: 10, 20, 30, 60, 90, 120, 240
CO2: 240, CO: 10, 20, 30, 60, 90, 120, 240
X
Ices were grown using background filling of the chamber at 1 x 10-5 torr. This is
approximately equivalent to an exposure 10 monolayer s-1. Assuming 1 monolayer is
2 – 5 Å, and uniform ice thickness, approximate ice thicknesses are:
Exposure Time (s)
Approx.
(μm)
10
20
30
60
90
120
240
900
0.0350
0.0700
0.105
0.210
0.315
0.420
0.840
3.15
Ice
Thickness
FTIR Settings
Parameter
Y-axis Maximum
Y-axis Minimum
Detector
Scan Speed
Delay
Aperture
Sample Beam
Resolution
Collect Sensitivity
Zero Filling Factor
Spectrum Type
Under-Sampling Ratio
No. of Scans
Low Pass Filter
Setting
4000 cm-1
400 cm-1
Internal Signal
5 kHz
1.0 s
For 0.5 cm-1
Not Installed
0.5 cm-1
8
4
Absorbance
2
128
1.12 kHz