A far-infrared beamline for ultrahigh vacuum surface vibrational spectroscopy at Aladdin

A far-infrared beamline has been implemented on port 031 of the Aladdin Storage Ring. Port 031 has been designed to capture the edge radiation produced by the fringe field of a bending magnet rather than normal bending magnet radiation. Calculations indicate that in cases where the aperture is limited edge radiation provides higher flux than bending magnets, particularly at the longer wavelengths. The far-infrared (IR) beamline shares this port with a mid-IR microscope beamline and uses the same optics to collect and collimate the light. To install the far-IR beamline, a special mirror was designed to deflect light to the purged bench and microscopes or to move out of the light path and allow the light to continue to the far-IR beamline. The vacuum bench employs a Thermo Nicolet interferometer with a solid substrate beamsplitter modified for use under rough vacuum. The light from the interferometer is focused through CsI windows on a sample in an ultrahigh vacuum chamber. The specular reflected light from the sample is collected by an elliptical mirror and focused onto a bolometer detector. The details of the beamline will be discussed as well as the first experimental results.