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Direct Absorption Spectroscopy at 1.1 THz: New Measurements of CrH (X6Σ+)
Rajat Ravi1, Deacon J Nemchick2, Brian J Drouin2
1Department of Chemistry and Biochemistry, University of Arizona, 1305 E. Fourth Street, Tucson, Arizona 85719, United States.
Pure rotational spectroscopy of chromium hydride (CrH) reveals detailed electronic structure. This study precisely measures hyperfine interactions, confirming unpaired electrons reside on the chromium atom.
Area of Science:
- Chemical Physics
- Molecular Spectroscopy
- Quantum Chemistry
Background:
- Chromium hydride (CrH) is a key molecule for understanding transition metal bonding.
- Previous studies lacked high-resolution rotational data for CrH.
Purpose of the Study:
- To record and analyze the pure rotational spectrum of CrH.
- To investigate the electronic structure and hyperfine interactions in CrH.
- To characterize the 53CrH isotopologue for the first time.
Main Methods:
- Direct absorption spectroscopy at 1.1 THz using a cascaded chain multiplier source.
- Measurement of N=3←2 transition for 52CrH and 53CrH isotopologues.
- Analysis using a Hund's case (b) Hamiltonian with advanced spin terms.
Main Results:
- Resolved proton hyperfine structure for 52CrH.
- Measured proton and 53Cr hyperfine splittings for 53CrH.
- Determined accurate rotational, fine structure, and hyperfine constants, including higher-order parameters.
- Established electronic configuration and orbital character of unpaired electrons.
Conclusions:
- The hyperfine constants confirm unpaired electrons are primarily on the chromium nucleus.
- The Fermi contact term indicates the unpaired σ electron has significant 3d character.
- This work provides crucial data for theoretical and experimental studies of transition metal hydrides.
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