Spin-Forbidden Carbon–Carbon Bond Formation in Vibrationally Excited α-CO

DeVine, Jessalyn A.; Choudhury, Arnab; Lau, Jascha A.; Schwarzer, Dirk; Wodtke, Alec M.

doi:10.1021/acs.jpca.2c01168

Cited by 8 publications

(17 citation statements)

References 47 publications

(104 reference statements)

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“…In the interstellar medium this is rather unlikely, but for the high fluxes used in the laboratory this should not be a priori neglected. As a consequence, some desorption mechanisms could in principle become accessible to CO molecules that collect energy from their neighbors and reach higher vibrational levels (DeVine et al 2022). Differently from DeVine et al ( 2022), however, we do not detect any photoinduced products upon irradiation of aCO nor cCO.…”

Section: Photodesorptioncontrasting

confidence: 81%

“…Differently from DeVine et al ( 2022), however, we do not detect any photoinduced products upon irradiation of aCO nor cCO. This is likely due to the differences between the experimental conditions of both studies (e.g., ice morphology, thickness, IR-photon generation method) that result in a significant quenching of the pooling effect during our experiments in comparison to DeVine et al (2022). Indeed, simultaneously excited species at any given time are expected to be very diluted within the ice in this work, as the number of absorption events per IR-FEL pulse is estimated to be much lower (∼0.1%) than the total ice column density.…”

Section: Photodesorptionmentioning

confidence: 89%

“…Vibrational energy pooling (VEP) is also an interesting phenomenon that takes place as a result of vibrational excitation. In VEP, vibrationally excited CO molecules pool their energy through a base-camp mechanism, resulting in highly excited CO species that constitute a small portion of the group (DeLeon & Rich 1986;Corcelli & Tully 2002;Chen et al 2017Chen et al , 2019DeVine et al 2022). DeVine et al (2022 have explored the effects of VEP of crystalline CO under interstellar conditions in a combined laboratory and theoretical work, and reported the formation of CO 2 and C 2 O 3 species as a result of spin-forbidden reactions involving highly vibrationally excited CO molecules.…”

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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Section: Photodesorptioncontrasting

confidence: 81%

Section: Photodesorptionmentioning

confidence: 89%

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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“…In VEP, vibrationally excited CO molecules pool their energy through a base-camp mechanism, resulting in highly excited CO species that constitute a small portion of the group (DeLeon & Rich 1986;Corcelli & Tully 2002;Chen et al 2017;Chen et al 2019;DeVine et al 2022). DeVine et al (2022 have explored the effects of VEP of crystalline CO under interstellar conditions in a combined laboratory and theoretical work, and reported the formation of CO 2 and C 2 O 3 species as a result of spin-forbidden reactions involving highly vibrationally excited CO molecules.…”

Section: Introductionmentioning

confidence: 99%

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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“…In the first, reactive, category, we have a contribution from DeVine et al, who address an issue of importance to astrobiology, namely, the formation of carbon−carbon bonds in reactions of vibrationally excited carbon monoxide in the interstellar medium. 7 By combining Fourier-transform infrared spectroscopy with high-quality theory, these authors identify mechanisms whereby, for example, C 3 O 2 is produced via a mechanism that passes the system through a spin-triplet manifold. Ion chemistry is also well-suited for study in cold gases.…”

mentioning

confidence: 99%