The missing halide: Millimeter-wave spectroscopy of the MgI radical (X 2Σ+)

K. M. Kilchenstein, D. T. Halfen, L. M. Ziurys

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


The pure rotational spectrum of the MgI radical in its ground electronic state (X 2Σ+) has been measured using millimeter/submillimeter wave direct absorption techniques in the region of 200–300 GHz. The molecule was created in a DC discharge by the reaction of magnesium vapor, produced in a Broida-type oven, with CH3I. Between five to twelve transitions were recorded for the v = 0, 1, and 2 vibrational states of 24MgI, as well as the v = 0 state for the isotopologues 25MgI and 26MgI, measured in their natural magnesium abundance. All observed transitions exhibited large spin-rotation splittings. Rotational, centrifugal distortion, and spin-rotation constants were determined for each isotopologue and the excited vibrational states of 24MgI. Equilibrium parameters Be, αe, De, βe, γe and γe were derived for the main isotopologue, as well as the equilibrium bond length, re = 2.5730 (1) Å. The large spin-rotation constant of γ ∼ 300 MHz in MgI is thought to arise from second-order spin-orbit coupling originating in the nearby A2Π state, with possible contributions from other excited 2Π states.

Original languageEnglish (US)
Pages (from-to)1-5
Number of pages5
JournalJournal of Molecular Spectroscopy
StatePublished - Sep 2017


  • Metal halides
  • MgI
  • Millimeter-wave spectroscopy
  • Spin-rotation interaction

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Spectroscopy
  • Physical and Theoretical Chemistry


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