Revisiting the Renner–Teller Effect in the X ̃\u3csup\u3e2\u3c/sup\u3e\u3cem\u3eΠ\u3c/em\u3e State of CCN: Pulsed Discharge-supersonic Jet Single Vibronic Level Emission Spectroscopy

Abstract

The CCN radical is a prototypical system for study of the Renner–Teller effect in its degenerate X ̃2Π ground state, with a number of experimental and theoretical studies carried out over the past 50 years. Most experimental studies have focused on the low-lying vibrational structure as observed in the high-resolution spectra of hot bands, or in emission. In this work, we have used pulsed-discharge supersonic-jet single vibronic level (SVL) emission spectroscopy from selected levels of the Ã2Δ state to probe the vibronic structure of X ̃2Π up to ∼6000 cm−1 above the vibrationless level. Around 50 levels were assigned, and these were fit to a Renner–Teller Hamiltonian to derive a detailed set of spectroscopic constants. Our data are compared with the results of recent high level coupled cluster calculations