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 N\(_2\), CO\(_2\), CF\(_4\) and C\(_6\)F\(_6\) are presented. Emitting species observed were N\(_2^+\) B\(^2\Sigma_u^+\) - X\(^2\Sigma_g^+\), CO\(_2^+\) A\(^2\Pi_u\) - X\(^2\Pi_g\) and B\(^2\Sigma_u^+\) - X\(^2\Pi_g\), CF\(_4\)\(^+\) C\(^2\)T\(_2\) - X\(^2\)T\(_1\) and C\(^2\)T\(_2\) - A\(^2\)T\(_2\), CF\(_3\)* \(^2\)A\(^’_2\) - \(^2\)A\(^”_2\), and C\(_6\)F\(_6^+\) B\(^2\)A\(_{2u}\) - X\(^2\)E\(_{1g}\). A CCD multi-channel detector has significantly reduced the time period needed to record dispersed fluorescence spectra with a comparable signal-to-noise ratio.