Velocity modulation spectroscopy of molecular ions I: The pure rotational spectrum of TiCl+ (X3Φr)

D. T. Halfen, L. M. Ziurys

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15 Scopus citations


The pure rotational spectrum of the TiCl+ ion in its X 3Φr ground state has been measured in the frequency range 323-424 GHz, using a combination of direct absorption and velocity modulation techniques. The ion was created in an AC discharge of TiCl 4 and argon. Ten, eleven, and nine rotational transitions were recorded for the 48Ti35Cl+, 48Ti37Cl+, and 46Ti 35Cl+ isotopomers, respectively; fine structure splittings were resolved in every transition. The rotational fine structure pattern was irregular with the Ω = 4 component lying in between the Ω = 2 and 3 lines. This result is consistent with the presence of a nearby 3Δr state, which perturbs the Ω = 2 and 3 sub-levels, shifting their energies relative to the Ω = 4 component. The data for each isotopomer were analyzed in a global fit, and rotational and fine structure parameters were determined. The value of the spin-spin constant was comparable to that of the spin-orbit parameter, indicating a large second-order spin-orbit contribution to this interaction. The bond length established for TiCl+, r0 = 2.18879 (7) Å, is significantly shorter than that of TiCl, which has r0 = 2.26749 (4) Å. The shorter bond length likely results from a Ti2+Cl- structure in the ion relative to the neutral, which is thought to be represented by a Ti +Cl- configuration. The higher charge on the titanium atom shortens the bond.

Original languageEnglish (US)
Pages (from-to)34-40
Number of pages7
JournalJournal of Molecular Spectroscopy
Issue number1
StatePublished - Nov 2005


  • Ions
  • Rotational
  • Spectroscopy

ASJC Scopus subject areas

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


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