A determination of the bond dissociation energy (D0(H-SH)):: Threshold ion-pair production spectroscopy (TIPPS) of a triatomic molecule

We present the first threshold ion-pair production spectrum of a triatomic molecule. We have recorded the ion-pair yield spectrum and TIPP spectrum for the H2S --> H++SH- ion-pair channel using single-photon excitation. From the TIPP spectrum, we have determined the H-SH bond energy (31451 +/- 4 cm(-1)) to unprecedented accuracy and demonstrated the formation of weakly bound H+-SH- (J') ion-pair states, with rotational excitation of the SH- anion up to J' = 4, The bound nature of these states, and the assigned spectrum that results from their field dissociation suggests that this technique can be applied to many other triatomic and larger polyatomic molecules in the future, leading to energetic, spectroscopic, and dynamical information about these species.