Integrated Intensities of Absorption Bands in Infrared Spectroscopy

Wexler, Arthur S.

doi:10.1080/05704926708547581

Cited by 149 publications

(36 citation statements)

References 177 publications

(161 reference statements)

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“…aliphatic versus aromatic hydrocarbons, carbonyl vs. alcohol carbon-oxygen chemical bonds, etc.). The following analysis utilizes the characteristic group frequencies as well as relative and intrinsic band strengths as described in (Bellamy 1960;Silverstein & Bassler 1967;Wexler 1967). The prominent features in these spectra are discussed systematically from higher to lower frequency.…”

Section: The Non-volatile Residuementioning

confidence: 99%

“…The spectrum of B ghi P is consistent with this analysis, but the bands are weaker. Given that the intrinsic strength of the aromatic C−H stretch is 10 times weaker than the intrinsic strength of the aliphatic C−H stretch per C−H (Wexler 1967), the increasing ratio of the aromatic band intensity to the aliphatic band intensity with PAH size indicates that H addition becomes less effective as the PAH size increases. -The 1700 cm −1 carbonyl C=O stretch: as with the O−H stretching band near 3 μm, some of this band may be attributed to the bending mode of H 2 O molecules frozen onto the cold sample window.…”

Section: The Non-volatile Residuementioning

confidence: 99%

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Photochemistry of polycyclic aromatic hydrocarbons in cosmic water ice

Bouwman

Mattioda

Linnartz

et al. 2010

A&A

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Context. Polycyclic aromatic hydrocarbons (PAHs) are known to be abundantly present in photon-dominated regions (PDRs), as evidenced by their ubiquitous mid-IR emission bands. Towards dense clouds, however, their IR emission bands are strongly suppressed. It is here where molecules are known to reside on very cold grains (T ≤ 30 K) in the form of interstellar ices. Therefore, it is likely that non-volatile species, such as PAHs, also freeze out on grains. Such icy grains act as catalytic sites and, upon vacuum ultraviolet (VUV) irradiation, chemical reactions are initiated. In the study presented here, these reactions and the resulting photoproducts are investigated for PAH containing water ices. Aims. The aim of this work is to monitor vacuum ultraviolet induced chemical reactions of PAHs in cosmic ice through their IR signatures, to characterize the families of species formed in these reactions, and to apply the results to astronomical observations. Methods. Mid-infrared Fourier transform absorption spectroscopic measurements ranging from 6500 to 450 cm −1 are performed on freshly deposited and vacuum ultraviolet processed PAH containing cosmic H 2 O ices at low temperatures. Results. The mid-IR spectroscopy of anthracene, pyrene and benzo[ghi]perylene containing H 2 O ice is reported. Band strengths of the neutral PAH modes in H 2 O ice are derived. Additionally, spectra of vacuum ultraviolet processed PAH containing H 2 O ices are presented. These spectra are compared to spectra measured in VUV processed PAH:argon matrix isolation studies. It is concluded that the parent PAH species is ionized in H 2 O ice and that other photoproducts, mainly more complex PAH derivatives, also form. The importance of PAHs and their PAH:H 2 O photoproducts in astronomical mid-infrared spectroscopic studies, in particular in the 5−8 μm region, is discussed. As a test-case, the VUV photolyzed PAH:H 2 O laboratory spectra are compared to a high resolution ISO-SWS spectrum of the high-mass embedded protostar W33A and to a Spitzer spectrum of the low-mass Young Stellar Object (YSO) RNO 91. For these objects, an upper limit of 2-3% with respect to H 2 O ice is derived for the contribution of PAHs and PAH:H 2 O photoproducts to the absorbance in the 5−8 μm region towards these objects.

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Section: The Non-volatile Residuementioning

confidence: 99%

Section: The Non-volatile Residuementioning

confidence: 99%

Photochemistry of polycyclic aromatic hydrocarbons in cosmic water ice

Bouwman

Mattioda

Linnartz

et al. 2010

A&A

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“…If electro-negative groups are attached to hydrocarbon chains, the intensity of the stretching mode at 3.4 µm decreases while the deformation mode at 6.85 µm becomes stronger (Wexler 1967). When an unsaturated group, such as a carbonyl group (C=O), is adjacent, the bending intensities are increased approximately 10 times in the 6.8-7.3 µm region,while the stretching intensities are reduced by a similar factor (Wexler 1967;d'Hendecourt & Allamandola 1986).…”

Section: The Effect Of Carbonyl and Nitrile Groupsmentioning

confidence: 99%

“…When an unsaturated group, such as a carbonyl group (C=O), is adjacent, the bending intensities are increased approximately 10 times in the 6.8-7.3 µm region,while the stretching intensities are reduced by a similar factor (Wexler 1967;d'Hendecourt & Allamandola 1986). The same effect is also observed if nitrile groups (C≡N) are attached, with no apparent shift in position of the bending and stretching modes.…”

Section: The Effect Of Carbonyl and Nitrile Groupsmentioning

confidence: 99%

Ice absorption features in the 5-8μm region toward embedded protostars

Keane¹,

Tielens

Boogert

et al. 2001

A&A

239

295

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Abstract.We have obtained 5-8 µm spectra towards 10 embedded protostars using the Short Wavelength Spectrometer on board the Infrared Space Observatory (ISO-SWS) with the aim of studying the composition of interstellar ices. The spectra are dominated by absorption bands at 6.0 µm and 6.85 µm. The observed peak positions, widths and relative intensities of these bands vary dramatically along the different lines of sight. On the basis of comparison with laboratory spectra, the bulk of the 6.0 µm absorption band is assigned to amorphous H2O ice. Additional absorption, in this band, is seen toward 5 sources on the short wavelength wing, near 5.8 µm, and the long wavelength side near 6.2 µm. We attribute the short wavelength absorption to a combination of formic acid (HCOOH) and formaldehyde (H2CO), while the long wavelength absorption has been assigned to the C-C stretching mode of aromatic structures. From an analysis of the 6.85 µm band, we conclude that this band is composed of two components: a volatile component centered near 6.75 µm and a more refractory component at 6.95 µm. From a comparison with various temperature tracers of the thermal history of interstellar ices, we conclude that the two 6.85 µm components are related through thermal processing. We explore several possible carriers of the 6.85 µm absorption band, but no satisfactory identification can be made at present. Finally, we discuss the possible implications for the origin and evolution of interstellar ices that arise from these new results.

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“…We use the value given by Kerkhof et al of 1.3 × 10 −17 cm molecule −1 , as usually done in the literature. For CH 3 CHO, we use the values given by Schutte et al (1999) and Wexler (1967) of 1.3 × 10 −17 cm molecule −1 for the CO stretch mode at 1715 cm −1 and 1.5 × 10 −18 cm molecule −1 for the CH bending mode at 1350 cm −1 . The thickness of the deposited solid films, assuming a density of 0.73 g cm −3 and 0.92 g cm −3 for NH 3 and H 2 O, respectively, is estimated to be around 0.1 μm, which is consistent with interstellar ice mantle thickness.…”

Section: Experimental and Theoreticalmentioning

confidence: 99%

Chiral molecule formation in interstellar ice analogs: alpha-aminoethanol NH₂CH(CH₃)OH

Duvernay

Dufauret

Danger

et al. 2010

A&A

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Aims. Aminoalcohol molecules such as alpha-aminoethanol NH 2 CH(CH 3 )OH may be aminoacid precursors. We attempt to characterize and detect this kind of molecules which is important to establish a possible link between interstellar molecules and life as we know it on Earth. Methods. We use Fourier transform infrared (FTIR) spectroscopy and mass spectrometry to study the formation of alphaaminoethanol NH 2 CH(CH 3 )OH in H 2 O:NH 3 : CH 3 CHO ice mixtures. Isotopic substitution with 15 NH 3 and ab-initio calculation are used to confirm the identification of alpha-aminoethanol. Results. After investigating the thermal reaction of solid NH 3 and acetaldehyde CH 3 CHO at low temperature, we find that this reaction leads to the formation of a chiral molecule, the alpha aminoethanol NH 2 CH(CH 3 )OH. For the first time, we report the infrared and mass spectra of this molecule. We also report on its photochemical behavior under VUV irradiation. We find that the main photoproduct is acetamide (NH 2 COCH 3 ). Data provided in this work indicates that alpha-aminoethanol is formed in one hour at 120 K and suggests that its formation in warm interstellar environments such as protostellar envelopes or cometary environments is likely.

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Integrated Intensities of Absorption Bands in Infrared Spectroscopy

Cited by 149 publications

References 177 publications

Photochemistry of polycyclic aromatic hydrocarbons in cosmic water ice

Photochemistry of polycyclic aromatic hydrocarbons in cosmic water ice

Ice absorption features in the 5-8μm region toward embedded protostars

Chiral molecule formation in interstellar ice analogs: alpha-aminoethanol NH₂CH(CH₃)OH

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Integrated Intensities of Absorption Bands in Infrared Spectroscopy

Cited by 149 publications

References 177 publications

Photochemistry of polycyclic aromatic hydrocarbons in cosmic water ice

Photochemistry of polycyclic aromatic hydrocarbons in cosmic water ice

Ice absorption features in the 5-8μm region toward embedded protostars

Chiral molecule formation in interstellar ice analogs: alpha-aminoethanol NH2CH(CH3)OH

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Product

Resources

About

Chiral molecule formation in interstellar ice analogs: alpha-aminoethanol NH₂CH(CH₃)OH