Vacuum ultraviolet spectroscopy of molecules of environmental and astrophysical interest using synchrotron radiation

Vacuum ultraviolet (VUV ∼6-25 eV) spectroscopy of polyatomic molecules is of considerable interest in many areas of physics, chemistry and biology. Its importance in the understanding of the various photochemical and photophysical processes in the atmosphere, astrophysical objects and biological systems etc. has been well recognized. VUV spectroscopic investigations in early days were often constrained by the limitations of traditional light sources which were either very weak or not continuously tunable. In the past few decades, synchrotron radiation has revolutionized VUV and soft X-ray spectroscopy, owing to its unique properties like high brilliance, continuous tenability, and well-defined pulsed time structure and polarization. India has two synchrotron sources, Indus-1 and lndus-2, at the Raja Ramanna Centre for Advanced Technology, Indore. In particular, the Indus-1 source, which is a 450 MeV storage ring with critical wavelength (λ_c) of 61 Å and a photon flux of 7 x 10¹¹ photons/sec/mrad/0.1% bandwidth at λ_c, is ideally suited for VUV spectroscopy. In this talk we discuss our very recent work on the VUV spectroscopy of molecules, particularly of environmental and astrophysical interest. An overview of the experimental and theoretical issues involved in this work will be presented with a focus on new findings. (author)