Energy Transfer and Restructuring in Amorphous Solid Water upon Consecutive Irradiation

Cuppen, H. M.; Noble, J. A.; Coussan, S.; Redlich, Britta; Ioppolo, Sergio

doi:10.1021/acs.jpca.2c06314

Cited by 6 publications

(7 citation statements)

References 34 publications

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“…Fredon et al (2021) have explored the dissipation of different types of energy (i.e., vibrational, rotational and translational) by admolecules on top of an ASW surface using molecular dynamics simulations. They observed that the distribution of vibrational energy among the species' vibrational modes heavily impacts the energy dissipation channels, in agreement with our experimental results and those of previous IR-FEL exposure works (Noble et al 2020;Ioppolo et al 2022;Coussan et al 2022;Cuppen et al 2022). They also concluded that the dissipation of vibrational energy from the admolecule to the surface occurs through the excitation of a surface-admolecule bond, and therefore intermolecular interactions play a key role in this processwhich is corroborated by our experimental results.…”

Section: Morphologysupporting

confidence: 92%

Resonant infrared irradiation of CO and CH3OH interstellar ices

Santos¹,

Chuang²,

Schrauwen³

et al. 2023

Preprint

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Context. Solid-phase photo-processes involving icy dust grains greatly affect the chemical evolution of the interstellar medium by leading to the formation of complex organic molecules and by inducing photodesorption. So far, the focus of laboratory studies has been mainly on the impact of energetic ultraviolet (UV) photons on ices, but direct vibrational excitation by infrared (IR) photons is expected to influence the morphology and content of interstellar ices as well. However, little is still known about the mechanisms through which this excess vibrational energy is dissipated, and its implications on the structure and ice photochemistry. Aims. In this work, we present a systematic investigation of the behavior of interstellar relevant CO and CH 3 OH ice analogues upon resonant excitation of vibrational modes using tunable infrared radiation, leading to both the quantification of infrared-induced photodesorption and insights in the impact of vibrational energy dissipation on ice morphology. Methods. We utilize an ultrahigh vacuum setup at cryogenic temperatures to grow pure CO and CH 3 OH ices, as well as mixtures of the two. We expose the ices to intense, near-monochromatic mid-infrared free-electron-laser radiation using the LISA end-station at the FELIX free electron laser facility to selectively excite the species. Changes to the ice are monitored by means of reflection-absorption infrared spectroscopy combined with quadrupole mass-spectrometry. The methods also allow to characterize the photodesorption efficiency.Results. The dissipation of vibrational energy is observed to be highly dependent on the excited mode and the chemical environment of the ice. All amorphous ices undergo some degree of restructuring towards a more organized configuration upon on-resonance irradiation. Moreover, IR-induced photodesorption is observed to occur for both pure CO and CH 3 OH ices, with interstellar photodesorption efficiencies of the order of 10 molecules cm −2 s −1 -i.e., comparable to or higher than UV-induced counterparts. Indirect photodesorption of CO upon vibrational excitation of CH 3 OH in ice mixtures is also observed to occur, particularly in environments rich in methanol. The astrochemical implications of these IR-induced phenomena are discussed.

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Section: Morphologysupporting

confidence: 92%

Resonant infrared irradiation of CO and CH3OH interstellar ices

Santos¹,

Chuang²,

Schrauwen³

et al. 2023

Preprint

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“…Furthermore, despite both ices containing the same column density of CO molecules, the higher abundance of surrounding CH 3 OH species in the methanol-rich ice results in more intense changes to the CO band, even upon irradiation at 4.67 µm. As was observed by Cuppen et al (2022) in H 2 O ices, it is likely that the higher fraction of hydrogen-bonded species in the CH 3 OH-rich mixture facilitates the vibrational energy transfer in comparison to the CO-rich counterpart, thus resulting in more intense spectral changes. In both ice mixtures, irradiations at the CHstretching bands of methanol (not shown) yield similar changes to the other modes, but less intense.…”

Section: Morphologymentioning

confidence: 62%

“…Alternatively, this difference could also be related to the type of intermolecular interactions within the ice, in which H-bonding networks could potentially facilitate the vibrational energy dissipation through restructuring, while generally weaker van der Waals interactions could be less efficient in doing so. Indeed, transfer of vibrational energy has been shown to occur in H 2 O ices through hydrogen-bonded water molecules with resonant O-H stretches, which leads to local heating and restructuring of the ice (Cuppen et al 2022).…”

Section: Morphologymentioning

confidence: 99%

“…Infrared-induced matrix-assisted laser desorption and ionization (MALDI) experiments ensued, evincing the photodesorption of polycyclic aromatic hydrocarbons (PAHs), as well as their hydrated clusters, embedded in water ice matrices and subjected to resonant vibrational excitation (Focsa et al 2006;Mihesan et al 2006;Henderson & Gudipati 2014). More recently, porous amorphous solid water (pASW) has been studied in works combining IR-free electron laser (FEL) irradiation experiments and molecular dynamics simulations, which revealed a reorganization of the ice structure towards a more ordered configuration upon the absorption of photons in the broad IR regime (Noble et al 2020;Coussan et al 2022;Cuppen et al 2022). Amorphous CO 2 ices have shown a similar behavior as a result of IR-FEL irradiation, whereas this effect was barely observed in the crystalline counterparts (Ioppolo et al 2022).…”

Section: Introductionmentioning

confidence: 99%

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Resonant infrared irradiation of CO and CH₃OH interstellar ices

Santos

Chuang

Schrauwen

et al. 2023

A&A

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Context. Solid-phase photo-processes involving icy dust grains greatly affect the chemical evolution of the interstellar medium by leading to the formation of complex organic molecules and by inducing photodesorption. So far, the focus of laboratory studies has mainly been on the impact of energetic ultraviolet (UV) photons on ices, but direct vibrational excitation by infrared (IR) photons is expected to influence the morphology and content of interstellar ices as well. However, little is still known about the mechanisms through which this excess vibrational energy is dissipated, as well as its implications for the structure and ice photochemistry. Aims. In this work, we present a systematic investigation of the behavior of interstellar relevant CO and CH3OH ice analogs following the resonant excitation of vibrational modes using tunable IR radiation. We seek to quantify the IR-induced photodesorption and gain insights into the impact of vibrational energy dissipation on ice morphology. Methods. We utilized an ultrahigh vacuum setup at cryogenic temperatures to grow pure CO and CH3OH ices, as well as mixtures of the two. We exposed the ices to intense, near-monochromatic mid-IR (MIR) free-electron-laser radiation using the LISA end-station at the FELIX free electron laser facility to selectively excite the species. Changes to the ice are monitored by means of reflection-absorption IR spectroscopy combined with quadrupole mass-spectrometry. These methods also allowed us to characterize the photodesorption efficiency. Results. The dissipation of vibrational energy is observed to be highly dependent on the excited mode and the chemical environment of the ice. All amorphous ices undergo some degree of restructuring towards a more organized configuration upon on-resonance irradiation. Moreover, IR-induced photodesorption is observed to occur for both pure CO and CH3OH ices, with interstellar photodesorption efficiencies on the order of 10 molecules cm−2 s−1. This result is comparable to or higher than what is found for UV-induced counterparts. An indirect photodesorption of CO upon vibrational excitation of CH3OH in ice mixtures is also observed to occur, particularly in environments that are rich in methanol. Here, we discuss the astrochemical implications of these IR-induced phenomena.

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“…Previous investigations of the effect of selective infrared irradiation of water ice have shown that desorption 40,41 and restructuring 42,43 of the water ice can take place, with the exact effects depending on which vibrational modes of the water are excited. A more recent study of the infrared free-electron laser irradiation of CO 2 ice 44 under astrophysically relevant conditions has also shown that restructuring of the ice, as well as photodesorption, occurs following irradiation with infrared light.…”

Section: Introductionmentioning

confidence: 99%