{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T13:14:27Z","timestamp":1788268467750,"version":"build-2803163510"},"reference-count":34,"publisher":"AIP Publishing","issue":"9","funder":[{"DOI":"10.13039\/501100001409","name":"Department of Science and Technology, Ministry of Science and Technology, India","doi-asserted-by":"publisher","award":["CRG\/2022\/003516"],"award-info":[{"award-number":["CRG\/2022\/003516"]}],"id":[{"id":"10.13039\/501100001409","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2026,9,7]]},"abstract":"<jats:p>Multiphoton ionization of pyrazine (Pyr) clusters generated in supersonic expansion was investigated using 266\u00a0nm UV excitation combined with time-of-flight mass spectrometry. Mass spectra revealed proton migration during the formation and dissociation of cluster cations, yielding protonated monomer [H+(Pyr)], dehydrogenated dimer [d-(Pyr)2+], and protonated trimer [H+(Pyr)3] ions. In addition, we report the first experimental observation of pyrazine\u2013water mixed clusters [(Pyr)n(H2O)m, n = 1\u20133, m = 1, 2] in a supersonic expansion, which had remained undetected in previous mass spectrometric studies. Their absence in earlier experiments is attributed to rapid relaxation and dissociation following single-photon excitation prior to ionization, whereas multiphoton excitation enables the formation and detection of bound ionic mixed-cluster complexes. The unusual ion-yield distribution of the mixed clusters, characterized by very weak signals for (Pyr)n(H2O)+ (n = 1 and 2) and a comparatively strong yield for (Pyr)3(H2O)+, is explained in terms of excited-state relaxation dynamics and cluster stability. Furthermore, photostability studies under intense focused laser irradiation (\u223c1011 W cm\u22122) demonstrate complete suppression of the parent cluster ions, accompanied by dominant formation of smaller fragment ions, including C3H3N+. These results provide insight into the photodissociation pathways of nitrogen-containing heterocyclic clusters and may have implications for the chemical evolution of such species in the interstellar medium.<\/jats:p>","DOI":"10.1063\/5.0347486","type":"journal-article","created":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T12:21:52Z","timestamp":1788265312000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Multiphoton ionization and proton transfer dynamics in (pyrazine)\n                    <i>n<\/i>\n                    clusters and (pyrazine)\n                    <i>n<\/i>\n                    (water)\n                    <i>m<\/i>\n                    (\n                    <i>n<\/i>\n                    = 1\u20133,\n                    <i>m<\/i>\n                    = 1, 2) mixed clusters"],"prefix":"10.1063","volume":"165","author":[{"ORCID":"https:\/\/orcid.org\/0009-0007-7449-6108","authenticated-orcid":false,"given":"Siddhartha S.","family":"Payra","sequence":"first","affiliation":[{"name":"Department of Physics, Indian Institute of Technology Madras , Chennai,","place":["India"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-1425-6620","authenticated-orcid":false,"given":"Pratikkumar","family":"Thakkar","sequence":"additional","affiliation":[{"name":"Department of Physics, Indian Institute of Technology Madras , Chennai,","place":["India"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-7766-8848","authenticated-orcid":false,"given":"Yash","family":"Lenka","sequence":"additional","affiliation":[{"name":"Department of Physics, Indian Institute of Technology Madras , Chennai,","place":["India"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4648-7136","authenticated-orcid":false,"given":"G.","family":"Aravind","sequence":"additional","affiliation":[{"name":"Department of Physics, Indian Institute of Technology Madras , Chennai,","place":["India"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"317","published-online":{"date-parts":[[2026,9,1]]},"reference":[{"key":"2026090108205428700_c1","doi-asserted-by":"publisher","first-page":"259","DOI":"10.1038\/s42004-023-01060-8","article-title":"Prebiotic chemical origin of biomolecular complementarity","volume":"6","year":"2023","journal-title":"Commun. 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