We have demonstrated a rovibrational-state-selected photoionization experiment using an IR laser and high-resolution VUV-synchrotron radiation. The VUV photoionization of acetylene [${\mathrm{C}}_2{\mathrm{H}}_2(\tilde{X}{}^1\Sigma _g^{+};{\nu }_3=1,J^{\prime }=8\mathrm{o}\mathrm{r}10)$] prepared by IR excitation reveals three strong autoionizing Rydberg series converging to ${\mathrm{C}}_2\mathrm{H}_2{}^{+}(\tilde{X}{}^2\Pi _u;{\nu }_3^{+}=1)$ with little ion background interference. Rotational transitions resolved for the Rydberg states provide an estimate of $\approx 1.8\mathrm{p}\mathrm{s}$ for their lifetimes. This experiment opens the way for state-selective photoionization studies of polyatomic molecules using VUV-synchrotron radiation.

• Received 17 July 2003

DOI:https://doi.org/10.1103/PhysRevLett.91.233001