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Title: The ortho-to-para ratio of H2Cl+: Quasi-classical trajectory calculations and new simulations in light of new observations

Journal Article · · Astronomy and Astrophysics
 [1];  [2];  [1];  [3];  [2];  [4]
  1. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Chemistry and Astronomy
  2. Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemistry and Chemical Biology
  3. Univ. de Montpellier, Montpellier (France). Lab. Univers et Particules de Montpellier
  4. Chalmers Univ. of Technology, Onsala (Sweden). Onsala Space Observatory, Dept. of Space, Earth and Environment
+ Show Author Affiliations

Multi-hydrogenated species with proper symmetry properties can present different spin configurations, and thus exist under different spin symmetry forms, labeled as para and ortho for two-hydrogen molecules. We investigated here the ortho-to-para ratio (OPR) of H2Cl+ in the light of new observations performed in the z = 0.89 absorber toward the lensed quasar PKS 1830-211 with the Atacama Large Millimeter/submillimeter Array (ALMA). Two independent lines of sight were observed, to the southwest (SW) and northeast (NE) images of the quasar, with OPR values found to be 3.15 ± 0.13 and 3.1 ± 0.5 in each region, respectively, in agreement with a spin statistical weight of 3:1. An OPR of 3:1 for a molecule containing two identical hydrogen nuclei can refer to either a statistical result or a high-temperature limit depending on the reaction mechanism leading to its formation. It is thus crucial to identify rigorously how OPRs are produced in order to constrain the information that these probes can provide. To understand the production of the H2Cl+ OPR, we undertook a careful theoretical study of the reaction mechanisms involved with the aid of quasi-classical trajectory calculations on a new global potential energy surface fit to a large number of high-level ab initio data. Our study shows that the major formation reaction for HH2Cl+ produces this ion via a hydrogen abstraction rather than a scrambling mechanism. Finally, such a mechanism leads to a 3:1 OPR, which is not changed by destruction and possible thermalization reactions for H2Cl+ and is thus likely to be the cause of observed 3:1 OPR ratios, contrary to the normal assumption of scrambling.

Research Organization:
Univ. of New Mexico, Albuquerque, NM (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
SC0015997
OSTI ID:
1540110
Journal Information:
Astronomy and Astrophysics, Vol. 608; ISSN 0004-6361
Publisher:
EDP SciencesCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 6 works
Citation information provided by
Web of Science

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Cited By (7)

Chlorine-bearing molecules in molecular absorbers at intermediate redshifts journal September 2019
Modeling deuterium chemistry in starless cores: full scrambling versus proton hop journal October 2019
The ortho-to-para ratio of water in interstellar clouds journal June 2019
Deuterated forms of H 3 + and their importance in astrochemistry
  • Caselli, P.; Sipilä, O.; Harju, J.
  • Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 377, Issue 2154 https://doi.org/10.1098/rsta.2018.0401
journal August 2019
The ortho-to-para ratio of water in interstellar clouds text January 2022
Modeling deuterium chemistry in starless cores: full scrambling versus proton hop text January 2019
Deuterated forms of H${_3^+}$ and their importance in astrochemistry preprint January 2019

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Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
Astronomy & Astrophysics
astrochemistry
ISM: molecules
quasars: individual: PKS 1830
211
galaxies: ISM
quasars: absorption lines
radio lines: galaxies