Clusters of betaine with positive and negative ions: Evidence for the betaine tetramer being magic

Adva Ben Yaacov, Lei Chen, Lihi Musbat, Maria Nihamkin, Alexander Kaiser, Yoni Toker

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Betaine (Bet) is a pure zwitterion with an extraordinarily large dipole moment, which allows it to form stable clusters in the gas phase of the form X±BetN, where X± is a positive or negative ion. We show here that such clusters have a prominent magic number at N = 4 for all X± ions used in this work. Nevertheless, we observe a marked difference in the fragmentation pattern of anionic and cationic clusters: While cationic clusters fragment by evaporating one betaine monomer at a time, fragmentation of anionic clusters is through fission resulting in the emission of one or several betaine molecules. Theoretical calculations show that charged betaine tetramers have a square like structure with the central ion lying above the cluster plane and explain the difference in fragmentation patterns as a result of the charge distribution within the betaine molecule.

Original languageEnglish
Article number184303
JournalJournal of Chemical Physics
Issue number18
StatePublished - 14 Nov 2019

Bibliographical note

Publisher Copyright:
© 2019 Author(s).


We are grateful to S. Brønsted Nielsen for insightful discussions and ideas on this work. This research was funded by the Israeli Science Foundation. L. Chen and A. Kaiser are grateful for the support from the Austrian Science Fund (FWF) Project No. P28979-N27, the Tiroler Science Fund (TWF) Project No. UNI-0404/2308, and the Förderkreis 1669 and AIANI from the University of Innsbruck.

FundersFunder number
Israeli Science Foundation
Tiroler Science Fund
Austrian Science FundP28979-N27
The Women's Foundation


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