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· 2 min read

Izaskun Jimenez-Serra has published a study of the chemistry of phosophorus bearing species using UCLCHEM. The paper can be found here and the abstract is below.

For decades, the detection of phosphorus-bearing molecules in the interstellar medium was restricted to high-mass star-forming regions (e.g., SgrB2 and Orion KL) and the circumstellar envelopes of evolved stars. However, recent higher-sensitivity observations have revealed that molecules such as PN and PO are present not only toward cold massive cores and low-mass star-forming regions with PO/PN ratios ≥1 but also toward the giant molecular clouds in the Galactic center known to be exposed to highly energetic phenomena such as intense UV radiation fields, shock waves, and cosmic rays. In this paper, we carry out a comprehensive study of the chemistry of phosphorus-bearing molecules across different astrophysical environments that cover a range of physical conditions (cold molecular dark clouds, warm clouds, and hot cores/hot corinos) and are exposed to different physical processes and energetic phenomena (proto-stellar heating, shock waves, intense UV radiation, and cosmic rays). We show how the measured PO/PN ratio (either ≥1, as in, e.g., hot molecular cores, or ≤1, as in UV strongly illuminated environments) can provide constraints on the physical conditions and energetic processing of the source. We propose that the reaction P + OH → PO + H, not included in previous works, could be an efficient gas-phase PO formation route in shocks. Our modeling provides a template with which to study the detectability of P-bearing species not only in regions in our own Galaxy but also in extragalactic sources.

· 2 min read
Jonathan Holdship

Audrey Coutens has published modelling work on glycoaldehyde and ethylene glycol using UCLCHEM. You can find the paper here and the abstract below.

Peptide bonds (N-C = O) play a key role in metabolic processes since they link amino acids into peptide chains or proteins. Recently, several molecules containing peptide-like bonds have been detected across multiple environments in the interstellar medium, growing the need to fully understand their chemistry and their role in forming larger pre-biotic molecules. We present a comprehensive study of the chemistry of three molecules containing peptide-like bonds: HNCO, NH2CHO, and CH3NCO. We also included other CHNO isomers (HCNO, HOCN) and C2H3NO isomers (CH3OCN, CH3CNO) to the study. We have used the UCLCHEM gas-grain chemical code and included in our chemical network all possible formation/destruction pathways of these peptide-like molecules recently investigated either by theoretical calculations or in laboratory experiments. Our predictions are compared to observations obtained towards the proto-star IRAS 16293-2422 and the L1544 pre-stellar core. Our results show that some key reactions involving the CHNO and C2H3NO isomers need to be modified to match the observations. Consistently with recent laboratory findings, hydrogenation is unlikely to produce NH2CHO on grain surfaces, while a combination of radical-radical surface reactions and gas-phase reactions is a better alternative. In addition, better results are obtained for NH2CHO when a slightly higher activation energy of 25 K is considered for the gas-phase reaction NH2 + H2CO → NH2CHO + H. Finally, our modelling shows that the observed correlation between NH2CHO and HNCO in star-forming regions may come from the fact that HNCO and NH2CHO react to temperature in the same manner rather than from a direct chemical link between the two species.

· 2 min read
Jonathan Holdship

David Quenard just published an update to the UCLCHEM with an application to COMs in prestellar cores you can find the paper here and the abstract below.

Peptide bonds (N-C = O) play a key role in metabolic processes since they link amino acids into peptide chains or proteins. Recently, several molecules containing peptide-like bonds have been detected across multiple environments in the interstellar medium, growing the need to fully understand their chemistry and their role in forming larger pre-biotic molecules. We present a comprehensive study of the chemistry of three molecules containing peptide-like bonds: HNCO, NH2CHO, and CH3NCO. We also included other CHNO isomers (HCNO, HOCN) and C2H3NO isomers (CH3OCN, CH3CNO) to the study. We have used the UCLCHEM gas-grain chemical code and included in our chemical network all possible formation/destruction pathways of these peptide-like molecules recently investigated either by theoretical calculations or in laboratory experiments. Our predictions are compared to observations obtained towards the proto-star IRAS 16293-2422 and the L1544 pre-stellar core. Our results show that some key reactions involving the CHNO and C2H3NO isomers need to be modified to match the observations. Consistently with recent laboratory findings, hydrogenation is unlikely to produce NH2CHO on grain surfaces, while a combination of radical-radical surface reactions and gas-phase reactions is a better alternative. In addition, better results are obtained for NH2CHO when a slightly higher activation energy of 25 K is considered for the gas-phase reaction NH2 + H2CO → NH2CHO + H. Finally, our modelling shows that the observed correlation between NH2CHO and HNCO in star-forming regions may come from the fact that HNCO and NH2CHO react to temperature in the same manner rather than from a direct chemical link between the two species.