Laser fluorescence excitation spectroscopy of the CAr van der Waals complex

Abstract

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.