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Updated: Jul 5, 2026

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Published on: August 18, 2017
High resolution probe of spin-orbit coupling and the singlet-triplet gap in chlorocarbene
Chong Tao1, Calvin Mukarakate, Richard H Judge
1Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, USA.
Abstract:
Among the most important of chemical intermediates are the carbenes, characterized by a divalent carbon that generates low-lying biradical (triplet) and spin-paired (singlet) configurations with unique chemical reactivities. The "holy grail" of carbene chemistry has been determining the singlet-triplet gap and intersystem crossing rates. We report here the first high resolution spectra of singlet-triplet transitions in a prototypical singlet carbene, CHCl, which probe in detail the triplet state structure and spin-orbit coupling with the ground singlet state. Our spectra reveal a pronounced vibrational state dependence of the triplet state spin-spin splitting parameter, which we show is a sensitive probe of spin-orbit coupling with nearby singlet states. The parameters derived from our spectra, including a precise determination of the singlet-triplet energy gap, are in excellent agreement with recent ab initio calculations.
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