Laser fluorescence excitation spectroscopy of the CAr van der Waals complex

Laser fluorescence excitation spectra of the CAr van der Waals complex, in the vicinity of the carbon 2s22p3s 3P°←2s22p2 3P and 2s2p3 3D°←2s22p2 3P atomic resonance transitions at 165.7 and 156.1 nm, respectively, are reported. A single, weak band was observed ∼100 cm−1 to the blue of the 2s22p3s 3P°←2s22p2 3P atomic transition. An excited-state (v′,0) progression correlating with the carbon atomic 2s2p3 3D°←2s22p2 3P transition was recorded near the 156.1 nm atomic transition and was assigned to the CAr F 3Π←X 3Σ− transition. The upper-state vibrational constants, ωe′ = 31.82±0.34 cm−1, ωexe′ = 3.58±0.11 cm−1, were determined. The excited F 3Π state was found to be less strongly bound than the ground state: D0′ = 54.8±1 and D0″ = 120.4±1 cm−1. Differences in the rotational contours of bands of the 12CAr to 13CAr isotopomers were ascribed to differences in the fine-structure splittings of the excited F 3Π state. The rotational constant Be′ = 0.112±0.005 cm−1 was estimated for the 12CAr isotopomer. A Morse function was constructed to describe the potential energy curve of the F 3Π state. The CAr binding energy is compared with that of other diatomic complexes, and the role of predissociation in the decay of excited CAr states is discussed. © 2000 American Institute of Physics.