Spectroscopy of the R-system (1 8 0) group band of CS 2 achieved by Λ-type excitation

Abstract

We have demonstrated a high resolution spectroscopic technique, the so-called Λ-type excitation, to re-investigate (1 8 0) group band of CS 2, which is closely located below the barrier of bent to linear. Λ-type excitation is a three-photon process. Rotationally resolved spectroscopy can be achieved as long as the chosen intermediate state can be rotationally resolved. Applying this technique, we are able to resolve the doublet due to the complexity of the potential near the bent-to-linear barrier top. And due to gaining a favorable Frank–Condor factor from the initial state (3 18 0), instead of (0 0 0), a combination mode having 2 ν 3 excitation induced by ν 2 mode Coriolis interaction was observed as well.