Hyperfine quantum beats and Zeeman spectroscopy in the polyatomic molecule propynal HC≡CCHO

Abstract

Quantum beats in the fluorescence decay of two single rovibronic levels of optically excited propynal (HC≡CCHO) have been measured in a supersonic jet apparatus. The complex beat pattern was explored using laser light of linear and circular polarization under zero-field conditions (nulled earth magnetic field) or in conjunction with an applied magnetic field. Theoretical aspects of molecular quantum beats were derived which include hyperfine coupling, magnetic field effects, and polarized excitation and detection. Singlet–triplet coupling matrix elements, Landé g-factors of the triplet hyperfine levels, and singlet and triplet decay rates have been determined.