Assessing the Formation of Solid Hydrogen Objects in Starless Molecular Cloud Cores

Levine, W. Garrett; Laughlin, Gregory

doi:10.3847/1538-4357/abec85

Cited by 18 publications

(3 citation statements)

References 56 publications

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“…That is not a new idea (e.g. White 1996), but the possibility that we might have actually observed one -in the form of the interstellar object 'Oumuamuais a fascinating recent development (Füglistaler & Pfenniger 2018;Seligman & Laughlin 2020;Levine & Laughlin 2021). Precisely because of their large dimensions, such objects will not contribute significantly to the absorption or emission on typical lines of sight.…”

Section: Macroscopic Bodies Of Solid H2mentioning

confidence: 88%

Absorption spectra of electrified hydrogen molecules

Walker

2022

Preprint

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Molecular hydrogen normally has only weak, quadrupole transitions between its rovibrational states, but in a static electric field it acquires a dipole moment and a set of allowed transitions. Here we use published ab initio calculations of the static electrical response tensors of the H 2 molecule to construct the perturbed rovibrational eigensystem and its ground state absorptions. We restrict attention to two simple field configurations that are relevant to condensed hydrogen molecules in the interstellar medium: a uniform electric field, and the field of a point-like charge. The energy eigenstates are mixtures of vibrational and angular momentum eigenstates so there are many transitions that satisfy the dipole selection rules. We find that mixing is strongest amongst the states with high vibrational excitation, leading to hundreds of absorption lines across the optical and near infrared. These spectra are very different to that of the field-free molecule, so if they appeared in astronomical data they would be difficult to assign. Furthermore in a condensed environment the excited states likely have short lifetimes to internal conversion, giving the absorption lines a diffuse appearance. We therefore suggest electrified H 2 as a possible carrier of the Diffuse Interstellar Bands (DIBs). We further argue that in principle it may be possible to account for all of the DIBs with this one carrier. However, despite electrification the transitions are not very strong and a large column of condensed H 2 would be required, making it difficult to reconcile this possibility with our current understanding of the ISM.

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Section: Macroscopic Bodies Of Solid H2mentioning

confidence: 88%

Absorption spectra of electrified hydrogen molecules

Walker

2022

Preprint

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“…This section would not be complete without mention of the possible existence of macroscopic bodies of solid hydrogen. That is not a new idea (e.g., White 1996), but the possibility that we might have actually observed one-in the form of the interstellar object 'Oumuamua-is a fascinating recent development (Füglistaler & Pfenniger 2018;Seligman & Laughlin 2020;Levine & Laughlin 2021). Precisely because of their large dimensions, such objects will not contribute significantly to the absorption or emission on typical lines of sight.…”

Section: Macroscopic Bodies Of Solid Hmentioning

confidence: 88%

Absorption Spectra of Electrified Hydrogen Molecules

Walker

2022

ApJ

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Molecular hydrogen normally has only weak, quadrupole transitions between its rovibrational states, but in a static electric field it acquires a dipole moment and a set of allowed transitions. Here we use published ab initio calculations of the static electrical response tensors of the H2 molecule to construct the perturbed rovibrational eigensystem and its ground state absorptions. We restrict attention to two simple field configurations that are relevant to condensed hydrogen molecules in the interstellar medium (ISM): a uniform electric field and the field of a pointlike charge. The energy eigenstates are mixtures of vibrational and angular momentum eigenstates so there are many transitions that satisfy the dipole selection rules. We find that mixing is strongest among the states with high vibrational excitation, leading to hundreds of absorption lines across the optical and near-infrared. These spectra are very different from that of the field-free molecule, so if they appeared in astronomical data they would be difficult to assign. Furthermore, in a condensed environment the excited states likely have short lifetimes to internal conversion, giving the absorption lines a diffuse appearance. We therefore suggest electrified H2 as a possible carrier of the diffuse interstellar bands (DIBs). We further argue that in principle it may be possible to account for all of the DIBs with this one carrier. However, despite electrification, the transitions are not very strong and a large column of condensed H2 would be required, making it difficult to reconcile this possibility with our current understanding of the ISM.

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“…It is unlikely to have an astroenvironment that is similar to rare-gas matrices for preserving the rotation of condensed water. Although it is unlikely that hydrogen can be directly solidified in most astroenvironments, according to recent reports H 2 can be adsorbed on amorphous water ice, 43 amorphous silicate (Mg 2 SiO 4 ), 44 carbonaceous grains, 45 and dust grains 46 at temperatures as high as 18 K. Hence, we propose a plausible route for the preferential formation of interstellar pH 2 O via the O + H 2 reaction. O 2 molecules adsorb on an interstellar grain surface covered with H 2 molecules and catalyze the conversion of the surrounding oH 2 to pH 2 .…”

mentioning

confidence: 99%

Formation of Para-H₂O by Vacuum-UV Photolysis of O₂ in Solid Hydrogen: Implication for Astrochemistry

Lin

Huang

Chou

et al. 2022

J. Phys. Chem. Lett.

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The observation that the ortho to para ratio (OPR) of interstellar H2O is smaller than 3 is an important yet unresolved subject in astronomy. We irradiated O2 embedded in solid H2 at 3 K with vacuum-ultraviolet (VUV) light and observed IR lines associated with para-H2O (denoted as pH2O) and nonrotating H2O–(oH2) n (where oH2 denotes ortho-H2) but no lines associated with ortho-H2O (denoted as oH2O). After maintaining the matrix in darkness for ∼30 h, the amount of pH2O decreased, accompanied by an increase in H2O–(oH2) n via diffusion of oH2. After that, the continuous nuclear-spin conversion from oH2 to para-H2 (denoted as pH2) in solid H2 over time resulted in the conversion of nonrotating H2O–(oH2) n to rotating pH2O in solid pH2. The observation of the formation and conversion of pH2O in our experiment suggests a plausible route in which VUV irradiation of O2 and H2 adsorbed on grain surfaces might be responsible for the smaller OPR of interstellar H2O.

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Assessing the Formation of Solid Hydrogen Objects in Starless Molecular Cloud Cores

Cited by 18 publications

References 56 publications

Absorption spectra of electrified hydrogen molecules

Absorption spectra of electrified hydrogen molecules

Absorption Spectra of Electrified Hydrogen Molecules

Formation of Para-H₂O by Vacuum-UV Photolysis of O₂ in Solid Hydrogen: Implication for Astrochemistry

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Assessing the Formation of Solid Hydrogen Objects in Starless Molecular Cloud Cores

Cited by 18 publications

References 56 publications

Absorption spectra of electrified hydrogen molecules

Absorption spectra of electrified hydrogen molecules

Absorption Spectra of Electrified Hydrogen Molecules

Formation of Para-H2O by Vacuum-UV Photolysis of O2 in Solid Hydrogen: Implication for Astrochemistry

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Formation of Para-H₂O by Vacuum-UV Photolysis of O₂ in Solid Hydrogen: Implication for Astrochemistry