Characterisation of a new VUV beamline at the Daresbury SRS using a dispersed fluorescence apparatus incorporating CCD detection

The design and performance of a new normal incidence monochromator at the Daresbury Synchrotron Radiation Source, optimised for experiments requiring high flux of vacuum-UV radiation, are described. The re-developed beamline 3.1, based on the Wadsworth design of monochromator, is the source of tunable vacuum-UV photons in the range 4-31 eV, providing over two orders of magnitude more flux than the vacuum-UV, Seya monochromator in its previous manifestation. The undispersed and dispersed fluorescence spectra resulting from photoexcitation of N2, CO2, CF4 and C6F6 are presented. Emitting species observed were N2+B2Σu+-X2Σg+, CO2+A˜2Πu-X˜2Πg and B˜2Σu+-X˜2Πg, CF4+C˜2T2-X˜2T1 and C˜2T2-A˜2T2, CF3∗2A2′-2A2, and C6F6+B˜2A2u-X˜2E1g. A CCD multi-channel detector has significantly reduced the time period needed to record dispersed fluorescence spectra with a comparable signal-to-noise ratio.