Rotational excitation of singly and doubly deuterated formaldehyde induced by collisions with molecular hydrogen
Abstract
This work presents calculations of state-to-state collisional rate coefficients for the rotational excitation of the deuterated formaldehyde isotopologs, HDCO and D2CO, induced by collisions with molecular hydrogen, coupled with experimental verification by pressurebroadening measurements. Time-independent scattering calculations were performed using the close-coupling method to compute inelastic cross sections for collisions with both para-H2 (j2 = 0) and ortho-H2 (j2 = 1). These calculations are based on the H2CO–H2 potential energy surface previously determined at the CCSD(T) level of theory and transformed to account for the isotopic substitution. The resulting rate coefficients cover the lowest 100 rotational states of HDCO and 60 states of ortho- and para-D2CO with internal energies less than 200 cm−1. Collisional data were obtained for temperatures up to 100 K for HDCO and D2CO and extended up to 300 K using the coupled-states approximation. The computed rate coefficients show systematic differences between ortho-H2 and para-H2 collisions, with the former generally yielding larger values by a factor of 2–3. Rate coefficients for HDCO–H2 are found to be lower by a factor of 2 to 3 compared to those of H2CO–H2 and D2CO–H2. Pressure-broadening coefficients were also calculated using the random-phase approximation and compared with new laboratory measurements, yielding agreement by about 5–30%.
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BibTeX
@article{pirlot2026rotational,
title = {{Rotational excitation of singly and doubly deuterated formaldehyde induced by collisions with molecular hydrogen}},
author = {Paul Pirlot and Takahiro Oyama and Alberto Macario Farto and Chinmai Sai Jureddy and Alexandre Faure and Ian R Sims and Nami Sakai},
journal = {Astronomy \& Astrophysics - A\&A},
year = {2026},
month = oct,
doi = {10.1051/0004-6361/202660504},
url = {https://hal.science/hal-05747016v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Rotational excitation of singly and doubly deuterated formaldehyde induced by collisions with molecular hydrogen
AU - Paul Pirlot
AU - Takahiro Oyama
AU - Alberto Macario Farto
AU - Chinmai Sai Jureddy
AU - Alexandre Faure
AU - Ian R Sims
AU - Nami Sakai
PY - 2026
DA - 2026/10/09
JO - Astronomy & Astrophysics - A&A
DO - 10.1051/0004-6361/202660504
UR - https://hal.science/hal-05747016v1
AB - This work presents calculations of state-to-state collisional rate coefficients for the rotational excitation of the deuterated formaldehyde isotopologs, HDCO and D2CO, induced by collisions with molecular hydrogen, coupled with experimental verification by pressurebroadening measurements. Time-independent scattering calculations were performed using the close-coupling method to compute inelastic cross sections for collisions with both para-H2 (j2 = 0) and ortho-H2 (j2 = 1). These calculations are based on the H2CO–H2 potential energy surface previously determined at the CCSD(T) level of theory and transformed to account for the isotopic substitution. The resulting rate coefficients cover the lowest 100 rotational states of HDCO and 60 states of ortho- and para-D2CO with internal energies less than 200 cm−1. Collisional data were obtained for temperatures up to 100 K for HDCO and D2CO and extended up to 300 K using the coupled-states approximation. The computed rate coefficients show systematic differences between ortho-H2 and para-H2 collisions, with the former generally yielding larger values by a factor of 2–3. Rate coefficients for HDCO–H2 are found to be lower by a factor of 2 to 3 compared to those of H2CO–H2 and D2CO–H2. Pressure-broadening coefficients were also calculated using the random-phase approximation and compared with new laboratory measurements, yielding agreement by about 5–30%.
SN - 0004-6361
SN - 1432-0746
ER -