Star and Planet Forming systems
Sandra Brünken, Olli Sipilä, Edward T. Chambers, Jorma Harju, Paola Caselli, Oskar Asvany, Cornelia E. Honingh, Tomasz Kamiński, Karl M. Menten, Jürgen Stutzki, and Stephan Schlemmer. “H2D+ observations give an age of at least one million years for a cloud core forming Sun-like stars”. Nature, 516(7530):219–221, December 2014.
https://doi.org/10.1038/nature13924.
L. Ilsedore Cleeves, Ryan A. Loomis, Richard Teague, Edwin A. Bergin, David J. Wilner, Jennifer B. Bergner, Geoffrey A. Blake, Jenny K. Calahan, Paolo Cazzoletti, Ewine F. van Dishoeck, Viviana V. Guzmán, Michiel R. Hogerheijde, Jane Huang, Mihkel Kama, Karin I. Öberg, Chunhua Qi, Jeroen Terwisscha van Scheltinga, and Catherine Walsh. “The TW Hya Rosetta Stone Project IV: A Hydrocarbon-rich Disk Atmosphere”. ApJ, 911(1):29, April 2021. https://doi.org/10.3847/1538-4357/abe862.
M. Gaillard, A. Faure, P. Hily-Blant, R. Le Gal, S. Lee, H. Nomura, and K. Furuya. “OrthoPara Chemistry of H2CO in the Protoplanetary Disk TW Hya”. ACS Earth and Space Chemistry, 10(3):687–696, March 2026. https://doi.org/10.1021/acsearthspacechem.5c00292.
Maryvonne Gerin, Harvey Liszt, Jérôme Pety, and Alexandre Faure. “H2CO and CS in diffuse clouds: Excitation and abundance”. A&A, 686:A49, June 2024. https://doi.org/10.1051/0004-6361/202449152.
V. Guzmán, J. Pety, J. R. Goicoechea, M. Gerin, and E. Roueff. “H2CO in the Horsehead PDR: photo-desorption of dust grain ice mantles”. A&A, 534:A49, October 2011. https://doi.org/10.1051/0004-6361/201117257.
V. V. Guzmán, K. I. Öberg, J. Carpenter, R. Le Gal, C. Qi, and J. Pagues. “H2CO Ortho-to-para Ratio in the Protoplanetary Disk HD 163296”. ApJ, 864(2):170, September 2018. https://doi.org/10.3847/1538-4357/aad778.
Claudio Hernández-Vera, Viviana V. Guzmán, Elizabeth Artur de la Villarmois, Karin I. Öberg, L. Ilsedore Cleeves, Michiel R. Hogerheijde, Chunhua Qi, John Carpenter, and Edith C. Fayolle. “Radial and Vertical Constraints on the Icy Origin of H2CO in the HD 163296 Protoplanetary Disk”. ApJ, 967(1):68, May 2024. https://doi.org/10.3847/1538-4357/ad3cdb.
J. K. Jørgensen, F. L. Schöier, and E. F. van Dishoeck. “H2CO and CH3OH abundances in the envelopes around low-mass protostars”. A&A, 437(2):501–515, July 2005. https://doi.org/10.1051/0004-6361:20042060.
C. Kahane, M. A. Frerking, W. D. Langer, P. Encrenas, and R. Lucas. “Measurement of the formaldehyde ortho to para ratio in three molecular clouds”. A&A, 137:211–222, August 1984.
C. M. Persson, A. O. H. Olofsson, R. Le Gal, E. S. Wirström, G. E. Hassel, E. Herbst, M. Ölberg, A. Faure, P. Hily-Blant, J. H. Black, M. Gerin, D. Lis, and F. Wyrowski. “Ortho-to-para ratio of NH2. Herschel-HIFI observations of ortho- and para-NH2 rotational transitions towards W31C, W49N, W51, and G34.3+0.1”. A&A, 586:A128, February 2016. https://doi.org/10.1051/0004-6361/201526781.
Chunhua Qi, Karin I. Öberg, and David J. Wilner. “H2CO and N2H+ in Protoplanetary Disks: Evidence for a CO-ice Regulated Chemistry”. ApJ, 765(1):34, March 2013. https://doi.org/10.1088/0004-637X/765/1/34.
C. M. Persson, M. De Luca, B. Mookerjea, A. O. H. Olofsson, J. H. Black, M. Gerin, E. Herbst, T. A. Bell, A. Coutens, B. Godard, J. R. Goicoechea, G. E. Hassel, P. Hily-Blant, K. M. Menten, H. S. P. Müller, J. C. Pearson, and S. Yu. “Nitrogen hydrides in interstellar gas. II. Analysis of Herschel/HIFI observations towards W49N and G10.6 – 0.4 (W31C).” A&A, 543:A145, July 2012. https://doi.org/10.1051/0004-6361/201118686.
M. Zannese, P. Guillard, A. Abergel, E. Habart, P. Dell’Ova, B. Trahin, J. Le Bourlot, K. Misselt, D. Van De Putte, A. N. Witt, K. D. Gordon, A. Noriega-Crespo, M. Baes, P. Bouchet, B. R. Brandl, M. Elyajouri, O. Kannavou, P. Klassen, and N. Ysard. “JWST observations of photodissociation regions: II. Warm molecular hydrogen spectroscopy in the Horsehead nebula”. A&A, 704:A202, December 2025. https://doi.org/10.1051/0004-6361/202556314
Comets and Solar System
Boncho P. Bonev, Geronimo L. Villanueva, Lucas Paganini, Michael A. DiSanti, Erika L. Gibb, Jacqueline V. Keane, Karen J. Meech, and Michael J. Mumma. “Evidence for two modes of water release in Comet 103P/Hartley 2: Distributions of column density, rotational temperature, and ortho-para ratio”. Icarus, 222(2):740–751, February 2013. https://doi.org/10.1016/j.icarus.2012.07.034.
Y.-C. Cheng, D. Bockelée-Morvan, M. Roos-Serote, J. Crovisier, V. Debout, S. Erard, P. Drossart, C. Leyrat, F. Capaccioni, G. Filacchione, M.-L. Dubernet, and T. Encrenaz. “Water ortho-to-para ratio in the coma of comet 67P/Churyumov-Gerasimenko”. A&A, 663:A43, July 2022. https://doi.org/10.1051/0004-6361/202142494.
Hideyo Kawakita, Junichi Watanabe, Reiko Furusho, Tetsuharu Fuse, Maria Teresa Capria, Maria Cristina De Sanctis, and Gabriele Cremonese. “Spin Temperatures of Ammonia and Water Molecules in Comets”. ApJ, 601(2):1152–1158, February 2004. https://doi.org/10.1086/380579.
Yoshiharu Shinnaka, Hideyo Kawakita, Emmanuel Jehin, Alice Decock, Damien Hutsemékers, and Jean Manfroid. “Ortho-to-para abundance ratios of NH2 in 26 comets: implications for the real meaning of OPRs”. MNRAS, 462:S124–S131, November 2016. https://doi.org/10.1093/mnras/stw2298.
Modelling and Laboratory
P. L. Chapovsky and A. A. Mamrashev. Nuclear spin conversion in H2O revisited. PhRvA, 104(5):052816, November 2021. https://doi.org/10.1103/PhysRevA.104.052816.
Pavel L. Chapovsky. Water ortho-para conversion by microwave background radiation in space. MNRAS, 503(2):1773–1779, May 2021. https://doi.org/10.1093/mnras/stab407.
A. Faure, P. Hily-Blant, R. Le Gal, C. Rist, and G. Pineau des Forêts. “Ortho-Para Selection Rules in the Gas-phase Chemistry of Interstellar Ammonia”. ApJL, 770(1):L2, June 2013. https://doi.org/10.1088/2041-8205/770/1/L2.
Tetsuya Hama, Akira Kouchi, and Naoki Watanabe. “The Ortho-to-para Ratio of Water Molecules Desorbed from Ice Made from Para-water Monomers at 11 K”. ApJL, 857(2):L13, April 2018. https://doi.org/10.3847/2041-8213/aabc0c.
Ardita Kilaj, Hong Gao, Daniel Rösch, Uxia Rivero, Jochen Küpper, and Stefan Willitsch. “Observation of different reactivities of para and ortho-water towards trapped diazenylium ions”. Nature Communications, 9:2096, May 2018. https://doi.org/10.1038/s41467-018-04483-3.
R. Le Gal, E. Herbst, C. Xie, A. Li, and H. Guo. “The ortho-to-para ratio of interstellar NH2: quasi-classical trajectory calculations and new simulations”. A&A, 596:A35, November 2016. https://doi.org/10.1051/0004-6361/201629107.
R. Le Gal, C. Xie, E. Herbst, D. Talbi, H. Guo, and S. Muller. “The ortho-to-para ratio of H2Cl+: Quasi-classical trajectory calculations and new simulations in light of new observations”. A&A, 608:A96, December 2017. https://doi.org/10.1051/0004-6361/201731566.
Alessandro Lupi, Stefano Bovino, and Tommaso Grassi. “On the low ortho-to-para H2 ratio in star-forming filaments”. A&A, 654:L6, October 2021. https://doi.org/10.1051/0004-6361/202142145.
L. Pagani, P. Lesaffre, M. Jorfi, P. Honvault, T. Gonz´alez-Lezana, and A. Faure. Ortho-H2 and the age of prestellar cores. A&A, 551:A38, March 2013. https://doi.org/10.1051/0004-6361/201117161.
N. Troscompt, A. Faure, S. Maret, C. Ceccarelli, P. Hily-Blant, and L. Wiesenfeld. “Constraining the ortho-to-para ratio of H2 with anomalous H2CO absorption”. Astronomy and Astrophysics, 506(3):1243–1247, November 2009. https://doi.org/10.1051/0004-6361/200912770.
K. M. Yocum, O. H. Wilkins, J. C. Bardwell, S. N. Milam, and P. A. Gerakines. “Gas-phase Ortho-to-para Ratio of Formaldehyde Formed at Low Temperatures in Laboratory Ices”. ApJL, 958(2):L41, December 2023. https://doi.org/10.3847/2041-8213/ad0bee.