ABSTRACT
We present a 1 + 1' resonance-enhanced multiphoton ionization (REMPI) scheme for acetylene via the linear GÌ 4sσ (1)Πu Rydberg state, offering partial rotational resolution and the possibility to detect excitation in both the cis- and trans-bending modes. The resonant transition to the GÌ state is driven by a vacuum ultraviolet (VUV) photon, generated by resonant four-wave mixing (FWM) in krypton. Ionization from the short-lived GÌ state then occurs quickly, driven by the high intensity of the residual light from the FWM process. We have observed nine bands in the region between 79â¯200 cm(-1) and 80â¯500 cm(-1) in C2H2 and C2D2. We compare our results with published spectra in this region and suggest alternative assignments for some of the Renner-Teller split bands. Similar REMPI schemes should be applicable to other small molecules with picosecond lifetime Rydberg states.
