Mass-analyzed threshold ionization spectroscopy of lanthanide imide LnNH (Ln = la and Ce) radicals from N-H bond activation of ammonia

Yuchen Zhang, Silver Nyambo, Dong Sheng Yang

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Ln (Ln = La and Ce) atom reactions with ammonia are carried out in a pulsed laser vaporization supersonic molecular beam source. Lanthanide-containing species are observed with time-of-flight mass spectrometry, and LnNH molecules are characterized by mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical calculations. The theoretical calculations include density functional theory for both Ln species and a scalar relativity correction, electron correlation, and spin-orbit coupling for the Ce species. The MATI spectrum of LaNH exhibits a single vibronic band system with a strong origin band and two weak vibronic progressions, whereas the spectrum of CeNH displays two band systems separated by 75 cm-1 with each being like the LaNH spectrum. By comparing with the theoretical calculations, both LaNH and CeNH are identified as linear molecules with C∞v symmetry, and the two vibronic progressions are attributed to the excitations of Ln-N stretching and Ln-N-H bending modes in the ions. The additional band system observed for CeNH is due to the spin-orbit splitting from the interactions of triplet and singlet states. The ground valence electron configurations of LaNH and CeNH are La 6s1 and Ce 4f16s1, and the ionization of each species removes the Ln 6s1 electron. The remaining two electrons that are associated with the isolated Ln atoms or ions are in a doubly degenerate molecular orbital that is a bonding combination between Ln 5dπ and N pπ orbitals.

Original languageEnglish
Article number234301
JournalJournal of Chemical Physics
Volume149
Issue number23
DOIs
StatePublished - Dec 21 2018

Bibliographical note

Funding Information:
We are grateful for the financial support from the National Science Foundation Division of Chemistry (Chemical Structure, Dynamics, and Mechanisms, Grant No. 1800316) and to Dr. Michael Schmidt for his help in relativistic calculations using the GAMESS quantum chemistry package.

Publisher Copyright:
© 2018 Author(s).

ASJC Scopus subject areas

  • Physics and Astronomy (all)
  • Physical and Theoretical Chemistry

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