Molecular fragmentation studies at the Indus-1 synchrotron

Interest in studying molecular fragmentation under various perturbations stems from the need to understand the effect of radiation on matter in stellar, biological and plasma environments, as also in the material science context. We have carried out a series of experiments on various molecules using soft X-rays from the Indus-1 synchrotron. We study photoionisation following the absorption of a single photon under single collision conditions. In most cases, our investigations were carried out using an ion momentum spectrometer, which is based on simultaneous spatial and temporal dispersion of ions in a uniform electric field. Ion flight time measurement is carried out by an electron-ion coincidence scheme, while the spatial dispersion is determined by employing a large area channel plate with a delay line anode. The focus of this series of experiments was on determining the fragmentation sequence and structural changes taking place as a result of multiple ionisation in small and large molecules. In the talk I shall dwell upon a few results from our work, that demonstrate the capabilities of the instrument and the rich information about molecular ions that can be had from molecular photoionisation experiments. This series of experiments is a result of a collaboration between PRL, Ahmedabad, lIT, Madras, and the Synchrotron Utilisation Division at RRCAT, Indore. (author)