Spectroscopic and lifetime measurements of C2 in the 33Πg and 43Πg states.

Spectroscopic and lifetime measurements of C2, one of the most important diatoms in the universe, provide valuable insights into its molecular structure, electronic transitions, and dissociation dynamics. In this work, we present an experimental investigation of the high-lying 33Πg and 43Πg states of C2 in the ultraviolet region. By using the resonance-enhanced multi-photon ionization (REMPI) scheme in combination with the spectral hole-burning technique, a new vibronic transition band assigned as 33Πgv' = 6-a3Πuv" = 5 is identified. The spectroscopic parameters are derived, and the vibrational levels of the 33Πg state are analyzed based on the newly obtained spectra. In addition, by employing the UV-pump-UV-probe scheme, the rotational state lifetimes in various vibrational levels of the 33Πg and 43Πg states are experimentally measured. The measurements reveal complex dependencies of the lifetimes on both the vibrational and rotational quantum numbers. Our findings advance the understanding of the excited state dynamics of C2 and underscore the further need for theoretical calculations to elucidate its high-lying potential energy surfaces and their mutual interactions, which are important for modeling the carbon chemistry in various gas environments.