Molecules in high spin states III: The millimeter/submillimeter-wave spectrum of the MnCl radical (X 7Σ +)

D. T. Halfen, Lucy M Ziurys

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The pure rotational spectrum of the MnCl radical (X 7Σ +) has been recorded in the range 141-535 GHz using millimeter-submillimeter direct absorption spectroscopy. This work is the first time the molecule has been studied with rotational resolution in its ground electronic state. MnCl was synthesized by the reaction of manganese vapor, produced in a Broida-type oven, with Cl 2. Transitions of both chlorine isotopomers were measured, as well as lines originating in several vibrationally excited states. The presence of several spin components and manganese hyperfine interactions resulted in quite complex spectra, consisting of multiple blended features. Because 42 rotational transitions were measured for Mn 35Cl over a wide range of frequencies with high signal-to-noise, a very accurate set of rotational, fine structure, and hyperfine constants could be determined with the aid of spectral simulations. Spectroscopic constants were also determined for Mn 37Cl and several vibrationally excited states. The values of the spin-rotation and spin-spin parameters were found to be relatively small (γ=11.2658 MHz and λ=1113.10 MHz for Mn 35Cl); in the case of λ, excited electronic states contributing to the second-order spin-orbit interaction may be canceling each other. The Fermi contact hyperfine term was found to be large in manganese chloride with b F(Mn 35Cl)=397.71MHz, a result of the manganese 4s character mixing into the 12σ orbital. This orbital is spσ hybridized, and contains some Mn 4pσ character, as well. Hence, it also contributes to the dipolar constant c, which is small and positive for this radical (c=32.35MHz for Mn 35Cl). The hyperfine parameters in MnCl are similar to those of MnH and MnF, suggesting that the bonding in these three molecules is comparable.

Original languageEnglish (US)
Article number054309
JournalThe Journal of Chemical Physics
Volume122
Issue number5
DOIs
StatePublished - 2005

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Submillimeter waves
submillimeter waves
Manganese
Millimeter waves
manganese
Electronic states
Excited states
Molecules
molecules
Chlorine
Ovens
Absorption spectroscopy
orbitals
ovens
rotational spectra
Orbits
spin-orbit interactions
Vapors
electronics
excitation

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Molecules in high spin states III : The millimeter/submillimeter-wave spectrum of the MnCl radical (X 7Σ +). / Halfen, D. T.; Ziurys, Lucy M.

In: The Journal of Chemical Physics, Vol. 122, No. 5, 054309, 2005.

Research output: Contribution to journalArticle

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abstract = "The pure rotational spectrum of the MnCl radical (X 7Σ +) has been recorded in the range 141-535 GHz using millimeter-submillimeter direct absorption spectroscopy. This work is the first time the molecule has been studied with rotational resolution in its ground electronic state. MnCl was synthesized by the reaction of manganese vapor, produced in a Broida-type oven, with Cl 2. Transitions of both chlorine isotopomers were measured, as well as lines originating in several vibrationally excited states. The presence of several spin components and manganese hyperfine interactions resulted in quite complex spectra, consisting of multiple blended features. Because 42 rotational transitions were measured for Mn 35Cl over a wide range of frequencies with high signal-to-noise, a very accurate set of rotational, fine structure, and hyperfine constants could be determined with the aid of spectral simulations. Spectroscopic constants were also determined for Mn 37Cl and several vibrationally excited states. The values of the spin-rotation and spin-spin parameters were found to be relatively small (γ=11.2658 MHz and λ=1113.10 MHz for Mn 35Cl); in the case of λ, excited electronic states contributing to the second-order spin-orbit interaction may be canceling each other. The Fermi contact hyperfine term was found to be large in manganese chloride with b F(Mn 35Cl)=397.71MHz, a result of the manganese 4s character mixing into the 12σ orbital. This orbital is spσ hybridized, and contains some Mn 4pσ character, as well. Hence, it also contributes to the dipolar constant c, which is small and positive for this radical (c=32.35MHz for Mn 35Cl). The hyperfine parameters in MnCl are similar to those of MnH and MnF, suggesting that the bonding in these three molecules is comparable.",
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