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• Journal article
  Ding M, Darvariu V-A, Ryabtsev AN, Hawes N, Pickering JCet al., 2026,
  , Communications Physics

  <jats:title>Abstract</jats:title> <jats:p> Atomic data determined by analysis of observed atomic spectra are essential for plasma diagnostics. For each low-ionisation open d- and f-subshell atomic species, around 10 <jats:sup>3</jats:sup> fine structure energy levels can be determined through years of analysis of 10 <jats:sup>4</jats:sup> observable spectral lines. We propose a partial automation of this task by casting the analysis procedure as a Markov decision process and solving it by graph reinforcement learning using reward functions partly learned on historical human decisions. In our evaluations on existing spectral line lists and theoretical calculations for Co II, Nd II and Nd III, hundreds of energy levels were identified and determined in hours, agreeing with published values in 95% of cases for Co II and 54–87% for Nd II and Nd III. As the current efficiency in atomic fine structure determination struggles to meet growing atomic data demands, our artificial intelligence approach sets the stage for closing this gap. </jats:p>

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• Journal article
  Clear CP, Uylings P, Raassen T, 2026,
  , Astronomy and Astrophysics (A & A), Vol: 706, ISSN: 0004-6361

  Aims. This work reports calculated transition probabilities for spectral lines of singly ionised nickel (Ni II) incorporating newly determined experimental energy levels, addressing critical gaps in atomic data required for astrophysical spectroscopy and plasma diagnostics.Methods. Transition probabilities of Ni II were calculated using the semi-empirical orthogonal operator method for both odd and even energy levels. Calculated eigenvalues were fine-tuned to experimental energy levels, determined using Fourier transform spectroscopy, further increasing the accuracy of these calculated transition probabilities.Results. In total, transition probabilities have been calculated for nearly 118 000 electric dipole transitions between 361 even and 735 odd levels. The resulting transition probabilities show strong agreement with existing experimental and semi-empirical data, while offering improved consistency and coverage across a wide range of line strengths. The calculated transitions span the far-infrared to the vacuum ultraviolet spectral regions, providing extensive coverage for astrophysical applications. This dataset significantly enhances the calculated atomic data available for Ni II and represents a critical contribution to the advancement of our understanding of astrophysical phenomena through improved spectroscopic analysis.

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• Journal article
  Ding M, Lim SZJ, Yu X, Clear CP, Pickering JCet al., 2025,
  , MACHINE LEARNING-SCIENCE AND TECHNOLOGY, Vol: 6
  • Cite
• Journal article
  Ding M, 2025,
  , ATOMS, Vol: 13
  • Cite
• Journal article
  Ding M, Kozuki H, Concepcion F, Nave G, Pickering JCet al., 2024,
  , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 536, Pages: 274-279, ISSN: 0035-8711
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• Journal article
  Ding M, Ryabtsev AN, Kononov EY, Ryabchikova T, Pickering JCet al., 2024,
  , ASTRONOMY & ASTROPHYSICS, Vol: 692, ISSN: 0004-6361
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• Journal article
  Ding M, Ryabtsev AN, Kononov EY, Ryabchikova T, Clear CP, Concepcion F, Pickering JCet al., 2024,
  , ASTRONOMY & ASTROPHYSICS, Vol: 684, ISSN: 0004-6361
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• Journal article
  Clear CP, Pickering JC, Nave G, Uylings P, Raassen Tet al., 2023,
  , ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, Vol: 269, ISSN: 0067-0049
  • Cite
• Journal article
  Basar G, Ozturk IK, Erdogan H, Bingol D, Guzelcimen F, Kroger S, Windholz L, Pickering JC, Basar Get al., 2023,
  , SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY, Vol: 207, ISSN: 0584-8547
  • Cite
  • Citations: 1
• Journal article
  Concepcion F, Clear CP, Ding M, Pickering JCet al., 2023,
  , EUROPEAN PHYSICAL JOURNAL D, Vol: 77, ISSN: 1434-6060
  • Cite
  • Citations: 1
• Journal article
  Clear CP, Uylings P, Raassen T, Nave G, Pickering JCet al., 2023,
  , Monthly Notices of the Royal Astronomical Society, Vol: 519, Pages: 4040-4046, ISSN: 0035-8711

  We report accurate Ritz wavelengths for parity-forbidden [Ni II] transitions, derived from energy levels determined using high-resolution Fourier transform spectroscopy. Transitions between the 18 lowest Ni II energy levels of even-parity produced Ritz wavelengths for 126 parity-forbidden lines. Uncertainties for the Ritz wavelengths derived in this work are up to two orders of magnitude lower than previously published values. Transition probabilities were calculated using the semi-empirical orthogonal operator method, with uncertainties ranging from approximately 1 per cent for strong M1 lines and up to 10 per cent for weak E2 lines. Accurate forbidden line wavelengths and transition probabilities, particularly for lines in the infrared, are important in the analyses of low-density astrophysical plasmas, such as supernova remnants, planetary nebulae, and active galactic nuclei.

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• Journal article
  Gilmore G, Randich S, Worley CC, Hourihane A, Gonneau A, Sacco GG, Lewis JR, Magrini L, Francois P, Jeffries RD, Koposov SE, Bragaglia A, Alfaro EJ, Allende Prieto C, Blomme R, Korn AJ, Lanzafame AC, Pancino E, Recio-Blanco A, Smiljanic R, Van Eck S, Zwitter T, Bensby T, Flaccomio E, Irwin MJ, Franciosini E, Morbidelli L, Damiani F, Bonito R, Friel ED, Vink JS, Prisinzano L, Abbas U, Hatzidimitriou D, Held E, Jordi C, Paunzen E, Spagna A, Jackson RJ, Maiz Apellaniz J, Asplund M, Bonifacio P, Feltzing S, Binney J, Drew J, Ferguson AMN, Micela G, Negueruela I, Prusti T, Rix H-W, Vallenari A, Bergemann M, Casey AR, de Laverny P, Frasca A, Hill V, Lind K, Sbordone L, Sousa SG, Adibekyan V, Caffau E, Daflon S, Feuillet DK, Gebran M, Gonzalez Hernandez J, Guiglion G, Herrero A, Lobel A, Montes D, Morel T, Ruchti G, Soubiran C, Tabernero HM, Tautvaisiene G, Traven G, Valentini M, Van der Swaelmen M, Villanova S, Vazquez CV, Bayo A, Biazzo K, Carraro G, Edvardsson B, Heiter U, Jofre P, Marconi G, Martayan C, Masseron T, Monaco L, Walton NA, Zaggia S, Borsen-Koch VA, Alves J, Balaguer-Nunez L, Barklem PS, Barrado D, Bellazzini M, Berlanas SR, Binks AS, Bressan A, Capuzzo-Dolcetta R, Casagrande L, Casamiquela L, Collins RS, D'Orazi V, Dantas MLL, Debattista VP, Delgado-Mena E, Di Marcantonio P, Drazdauskas A, Evans NW, Famaey B, Franchini M, Fremat Y, Fu X, Geisler D, Gerhard O, Solares EAG, Grebel EK, Gutierrez Albarran ML, Jimenez-Esteban F, Jonsson H, Khachaturyants T, Kordopatis G, Kos J, Lagarde N, Ludwig H-G, Mahy L, Mapelli M, Marfil E, Martell SL, Messina S, Miglio A, Minchev I, Moitinho A, Montalban J, Monteiro MJPFG, Morossi C, Mowlavi N, Mucciarelli A, Murphy DNA, Nardetto N, Ortolani S, Paletou F, Palous J, Pickering JC, Quirrenbach A, Fiorentin PR, Read J, Romano D, Ryde N, Sanna N, Santos W, Seabroke GM, Spina L, Steinmetz M, Stonkute E, Sutorius E, Thevenin F, Tosi M, Tsantaki M, Wright N, Wyse RFG, Zoccali M, Zorec J, Zucker DBet al., 2022,
  , ASTRONOMY & ASTROPHYSICS, Vol: 666, ISSN: 0004-6361
  • Cite
  • Citations: 100
• Journal article
  Randich S, Gilmore G, Magrini L, Sacco GG, Jackson RJ, Jeffries RD, Worley CC, Hourihane A, Gonneau A, Vazquez CV, Franciosini E, Lewis JR, Alfaro EJ, Allende Prieto C, Bensby T, Blomme R, Bragaglia A, Flaccomio E, Francois P, Irwin MJ, Koposov SE, Korn AJ, Lanzafame AC, Pancino E, Recio-Blanco A, Smiljanic R, Van Eck S, Zwitter T, Asplund M, Bonifacio P, Feltzing S, Binney J, Drew J, Ferguson AMN, Micela G, Negueruela I, Prusti T, Rix H-W, Vallenari A, Bayo A, Bergemann M, Biazzo K, Carraro G, Casey AR, Damiani F, Frasca A, Heiter U, Hill V, Jofre P, de Laverny P, Lind K, Marconi G, Martayan C, Masseron T, Monaco L, Morbidelli L, Prisinzano L, Sbordone L, Sousa SG, Zaggia S, Adibekyan V, Bonito R, Caffau E, Daflon S, Feuillet DK, Gebran M, Gonzalez Hernandez J, Guiglion G, Herrero A, Lobel A, Maiz Apellaniz J, Merle T, Mikolaitis S, Montes D, Morel T, Soubiran C, Spina L, Tabernero HM, Tautvaisiene G, Traven G, Valentini M, Van der Swaelmen M, Villanova S, Wright NJ, Abbas U, Borsen-Koch VA, Alves J, Balaguer-Nunez L, Barklem PS, Barrado D, Berlanas SR, Binks AS, Bressan A, Capuzzo-Dolcetta R, Casagrande L, Casamiquela L, Collins RS, D'Orazi V, Dantas MLL, Debattista VP, Delgado-Mena E, Di Marcantonio P, Drazdauskas A, Evans NW, Famaey B, Franchini M, Fremat Y, Friel ED, Fu X, Geisler D, Gerhard O, Solares EAG, Grebel EK, Gutierrez Albarran ML, Hatzidimitriou D, Held E, Jimenez-Esteban F, Jonsson H, Jordi C, Khachaturyants T, Kordopatis G, Kos J, Lagarde N, Mahy L, Mapelli M, Marfil E, Martell SL, Messina S, Miglio A, Minchev I, Moitinho A, Montalban J, Monteiro MJPFG, Morossi C, Mowlavi N, Mucciarelli A, Murphy DNA, Nardetto N, Ortolani S, Paletou F, Palous J, Paunzen E, Pickering JC, Quirrenbach A, Fiorentin PR, Read J, Romano D, Ryde N, Sanna N, Santos W, Seabroke GM, Spagna A, Steinmetz M, Stonkute E, Sutorius E, Thevenin F, Tosi M, Tsantaki M, Vink JS, Wright N, Wyse RFG, Zoccali M, Zorec J, Zucker DB, Walton NAet al., 2022,
  , ASTRONOMY & ASTROPHYSICS, Vol: 666, ISSN: 0004-6361
  • Cite
  • Citations: 121
• Journal article
  Ding M, Pickering JC, 2022,
  , JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, Vol: 288, ISSN: 0022-4073
  • Cite
  • Citations: 3
• Journal article
  Clear CP, Pickering JC, Nave G, Uylings P, Raassen Tet al., 2022,
  , The Astrophysical Journal Supplement Series, Vol: 261, Pages: 35-35, ISSN: 0067-0049

  High-resolution spectra of singly ionized nickel (Ni ii) have been recorded using Fourier transform spectroscopy in the region 143–5555 nm (1800–70,000 cm−1) with continuous, nickel–helium hollow cathode discharge sources. An extensive analysis of identified Ni ii lines resulted in the confirmation and revision of 283 previously reported energy levels, from the ground state up to the 3d8(ML)6s subconfigurations. Typical energy-level uncertainties are a few thousandths of a cm−1, representing at least an order-of-magnitude reduction in uncertainty with respect to previous measurements. Twenty-five new energy levels have now been established and are reported here for the first time. Eigenvector compositions of the energy levels have been calculated using the orthogonal operator method. In total, 159 even and 149 odd energy levels and 1424 classified line wavelengths of Ni ii are reported and will enable more accurate and reliable analyses of Ni ii in astrophysical spectra.

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• Journal article
  Weiss Z, Concepcion-Mairey F, Pickering JC, Smid Pet al., 2021,
  , SPECTROCHIMICA ACTA PART B-ATOMIC SPECTROSCOPY, Vol: 180, ISSN: 0584-8547
  • Cite
  • Citations: 2
• Journal article
  Nave G, Clear C, 2021,
  , MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 502, Pages: 5679-5685, ISSN: 0035-8711
  • Cite
• Journal article
  Liggins FS, Pickering JC, Nave G, Kramida A, Gamrath S, Quinet Pet al., 2021,
  , ASTROPHYSICAL JOURNAL, Vol: 907, ISSN: 0004-637X
  • Cite
  • Citations: 2
• Journal article
  Heiter U, Lind K, Bergemann M, Asplund M, Mikolaitis S, Barklem PS, Masseron T, de Laverny P, Magrini L, Edvardsson B, Jonsson H, Pickering JC, Ryde N, Aran AB, Bensby T, Casey AR, Feltzing S, Jofre P, Korn AJ, Pancino E, Damiani F, Lanzafame A, Lardo C, Monaco L, Morbidelli L, Smiljanic R, Worley C, Zaggia S, Randich S, Gilmore GFet al., 2021,
  , ASTRONOMY & ASTROPHYSICS, Vol: 645, ISSN: 0004-6361
  • Cite
  • Citations: 70
• Journal article
  Liggins FS, Pickering JC, Nave G, Ward JW, Tchang-Brillet W-ULet al., 2021,
  , ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, Vol: 252, ISSN: 0067-0049
  • Cite
  • Citations: 5

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