Measurements of\nthe Rovibrationally Dependent Lifetimes\nof C<sub>2</sub> in the 1<sup>3</sup>Σ<sub>g</sub><sup>+</sup> and <i>f</i><sup>3</sup>Σ<sub>g</sub><sup&

The\ndicarbon molecule, C<sub>2</sub>, is one of the most important\ndiatomic species in various gaseous environments. Despite extensive\nspectroscopic studies in the last two centuries, the radiative and\nphotodissociative properties of C<sub>2</sub> in its highly excited\nelectronic states are still largely unexplored, particularly in the\nshort vacuum ultraviolet (VUV) region. In this study, the lifetimes\nof C<sub>2</sub> for rotational levels in the recently identified\n1<sup>3</sup>Σ<sub>g</sub><sup>+</sup> state up to the vibrational\nlevel ν′ = 4 and in the <i>f</i><sup>3</sup>Σ<sub>g</sub><sup>–</sup> state up to ν′\n= 2 are measured for the first time with a VUV-pump–UV-probe\nphotoionization scheme. It is found that all rovibrational levels\nin the <i>f</i><sup>3</sup>Σ<sub>g</sub><sup>–</sup> state have lifetimes shorter than the dynamical limit of ∼4.7\nns of the present method, and the lifetimes in the 1<sup>3</sup>Σ<sub>g</sub><sup>+</sup> state show obvious and complex dependence on\nthe rotational and vibrational quantum levels. Generally, the lifetime\nin the 1<sup>3</sup>Σ<sub>g</sub><sup>+</sup> state becomes\nshorter at higher rotational and vibrational levels, i.e., the longest\nlifetime measured in the ν′ = 0 level is ∼18 ns,\nwhile all rotational levels in the ν′ = 4 level are found\nto have shorter lifetimes than ∼4.7 ns. This implies that predissociation\nmight occur and become more prominent at the higher energy levels\nin the 1<sup>3</sup>Σ<sub>g</sub><sup>+</sup> state. The prominent\ndependence of the lifetime on the rotational, vibrational and electronic\nlevel indicates complex dynamical processes in the highly excited\nstates of C<sub>2</sub>.