J/ApJ/743/131 Infrared absorbance of water H2O/H2O2 ice (Smith+, 2011)
On the formation of interstellar water ice: constraints from a search for
hydrogen peroxide ice in molecular clouds.
Smith R.G., Charnley S.B., Pendleton Y.J., Wright C.M., Maldoni M.M.,
Robinson G.
<Astrophys. J., 743, 131 (2011)>
=2011ApJ...743..131S 2011ApJ...743..131S
ADC_Keywords: Abundances ; Interstellar medium ; Spectra, infrared
Keywords: infrared: ISM - ISM: abundances - ISM: clouds - ISM: lines and bands -
ISM: molecules - molecular processes
Abstract:
Recent surface chemistry experiments have shown that the hydrogenation
of molecular oxygen on interstellar dust grains is a plausible
formation mechanism, via hydrogen peroxide (H2O2), for the
production of water (H2O) ice mantles in the dense interstellar
medium. Theoretical chemistry models also predict the formation of a
significant abundance of H2O2 ice in grain mantles by this route.
At their upper limits, the predicted and experimental abundances are
sufficiently high that H2O2 should be detectable in molecular
cloud ice spectra. To investigate this further, laboratory spectra
have been obtained for H2O2/H2O ice films between 2.5 and 200um,
from 10 to 180K, containing 3%, 30%, and 97% H2O2 ice. Integrated
absorbances for all the absorption features in low-temperature
H2O2 ice have been derived from these spectra. For identifying
H2O2 ice, the key results are the presence of unique features near
3.5, 7.0, and 11.3um. Comparing the laboratory spectra with the
spectra of a group of 24 protostars and field stars, all of which have
strong H2O ice absorption bands, no absorption features are found
that can definitely be identified with H2O2 ice. In the absence of
definite H2O2 features, the H2O2 abundance is constrained by
its possible contribution to the weak absorption feature near 3.47um
found on the long-wavelength wing of the 3um H2O ice band. This
gives an average upper limit for H2O2, as a percentage of H2O,
of 9%±4%. This is a strong constraint on parameters for surface
chemistry experiments and dense cloud chemistry models.
Description:
The laboratory setup used to make the infrared spectral measurements
of thin H2O2/H2O ice films has already been described by Smith
et al. (1994MNRAS.271..481S 1994MNRAS.271..481S) and Maldoni et al. (1998MNRAS.298..251M 1998MNRAS.298..251M).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 120 1849 Absorbance data for the 3% near-infrared 2.5-25um
(4000-400cm-1) H2O2/H2O ice films
table3.dat 131 1849 Absorbance data for the 30% near-infrared 2.5-25um
(4000-400cm-1) H2O2/H2O ice films
table4.dat 153 1849 Absorbance data for the 97% near-infrared 2.5-25um
(4000-400cm-1) H2O2/H2O ice films
table5.dat 120 235 Absorbance data for the 3% far-infrared 20-200um
(500-50cm-1) H2O2/H2O ice films
table6.dat 120 235 Absorbance data for the 30% far-infrared 20-200um
(500-50cm-1) H2O2/H2O ice films
table7.dat 142 235 Absorbance data for the 97% far-infrared 20-200um
(500-50cm-1) H2O2/H2O ice films
table10.dat 46 24 Upper limits to the H2O2 ice abundances,
relative to H2O ice, for a selection of
protostars and field stars based on the optical
depth at 3.50um within the 3.47um feature
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See also:
J/ApJ/701/1347 : Optical constants of H2O-ice (Mastrapa+, 2009)
J/ApJ/678/985 : c2d Spitzer survey of interstellar ices. I. (Boogert+, 2008)
J/ApJ/684/1240 : Prestellar cores in Perseus, Serpens & Oph (Enoch+, 2008)
J/ApJS/86/713 : IR spectroscopy of ices (Hudgins+, 1993)
Byte-by-byte Description of file: table[234567].dat
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Bytes Format Units Label Explanations
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1- 10 E10.5 cm-1 sigma Wavenumber
12- 21 E10.3 --- Abs10 Absorbance at 10K
23- 32 E10.3 --- Abs30 Absorbance at 30K
34- 43 E10.3 --- Abs50 Absorbance at 50K
45- 54 E10.3 --- Abs70 Absorbance at 70K
56- 65 E10.3 --- Abs90 Absorbance at 90K
67- 76 E10.3 --- Abs110 Absorbance at 110K
78- 87 E10.3 --- Abs120 Absorbance at 120K
89- 98 E10.3 --- Abs130 Absorbance at 130K
100-109 E10.3 --- Abs140 Absorbance at 140K
111-120 E10.3 --- Abs150 Absorbance at 150K
122-131 E10.3 --- Abs160 ? Absorbance at 160K (for tables 3, 4 and 7)
133-142 E10.3 --- Abs170 ? Absorbance at 170 K (only for tables 4 and 7)
144-153 E10.3 --- Abs180 ? Absorbance at 180 K (only for table 4)
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Byte-by-byte Description of file: table10.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Group "Processed" or "Unprocessed" (1)
13- 28 A16 --- Name Source name
30- 33 F4.2 --- tau3.08 Optical depth τ at 3.08um
35- 38 F4.2 --- tau3.50 Optical depth τ at 3.50um
40- 41 I2 % H2O2 H2O2 ice abundance relative to H2O ice
43- 46 A4 --- Ref Reference(s) (2)
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Note (1): Sources have been divided into two groups on the basis of the
appearance of the 3.08um H2O ice absorption feature in their spectra
which reflects different levels of thermal processing of the ice (see,
e.g., the discussion in Smith et al. 1989ApJ...344..413S 1989ApJ...344..413S). For
protostars in the "unprocessed" group their 3.08um H2O ice
absorption features are typical of 10-20K amorphous ice while the
"processed" group have 3.08um features which are narrower and contain
substructure consistent with exposure to higher temperatures.
See section 2.4 for further explanations.
Note (2): Reference as follows:
1 = Willner et al. 1982ApJ...253..174W 1982ApJ...253..174W
2 = Smith et al. 1989ApJ...344..413S 1989ApJ...344..413S
3 = Brooke et al. 1996ApJ...459..209B 1996ApJ...459..209B
4 = Whittet et al. 1988MNRAS.233..321W 1988MNRAS.233..321W
5 = Sato et al. 1990ApJ...359..192S 1990ApJ...359..192S
6 = Chiar et al. 1996ApJ...472..665C 1996ApJ...472..665C
7 = Brooke et al. 1999ApJ...517..883B 1999ApJ...517..883B
8 = Sellgren et al. 1994ApJ...433..179S 1994ApJ...433..179S
9 = Boogert et al. 2000A&A...360..683B 2000A&A...360..683B
10 = Tanaka et al. 1990ApJ...352..724T 1990ApJ...352..724T
11 = Kastner & Weintraub 1996ApJ...466L.103K 1996ApJ...466L.103K
12 = Eiroa & Hodapp 1989A&A...210..345E 1989A&A...210..345E
13 = Whittet et al. 1996ApJ...458..363W 1996ApJ...458..363W
14 = Tanaka et al. 1994ApJ...430..779T 1994ApJ...430..779T
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 07-May-2013