Characterising S(¹D) atoms formed by exciting D₂S molecules via intense Rydberg resonances at wavelengths ~139.1 nm and ~129.1 nm

We report high-resolution velocity map imaging studies of S(¹D) atoms formed following excitation on two intense absorption bands of gas phase D₂S molecules, centred at wavelengths ~139.1 and ~129.1 nm. DS–D bond fission is the dominant fragmentation pathway at these wavelengths, yielding SD fragments in both the ground (X) and excited (A) electronic states. Most S(¹D) atoms arising via the rival S atom elimination channel when exciting at ~139.1 nm are formed with D₂ partners, in a wide range of rovibrational levels. The partially resolved structure in the total translational energy distributions, P(ET), derived from the S(¹D) atom images, implies two dynamical routes into S(¹D)+D2 products following non-adiabatic coupling from the photo-excited Rydberg state to the dissociative 2¹ A´ potential energy surface (PES). Similar D2 products are evident in the P(ET) spectra derived from analysis of S(1D) images from D2S photolysis at ~129.1 nm, but their contribution is overshadowed by a feature attributable to three-body dissociation to S(1D) + 2D fragments. These atomic products are deemed to arise via a natural extension of the dynamics responsible for the previously observed highly rotationally excited SD(A) fragments arising via the rival S–D bond fission pathway: asymmetric bond extension together with a dramatic opening of the interbond angle driven by torques generated after coupling to the highly anisotropic 2¹ A´ PES, leading to a centripetally-driven break-up.