STATION 3.2
McPherson monochromator

Description

Atomic and Molecular Science:

• Angle resolved photoelectron spectroscopy,
• Threshold photoelectron spectroscopy,
• Photoelectron-photoion coincidence spectrometry
• Photo-double-ionisation,
• Fluorescent yield and photoionisation cross-section measurement.

Surface Science:

• Luminescence excitation and emission spectroscopy,
• Low temperature, high resolution photoelectron spectroscopy.

News

Upgrade Programme Completed
The beamline upgrade programme has been completed with the installation, in March 2003, of a new ellipsoidal premirror in the 11.6m mirrorbox. The severely contaminated Low Energy Grating has been removed for refurbishment: installation of the renovated grating is planned for October 2004

The chassis of the High Resolution Photoelectron Spectroscopy chamber has been modified to enable direct linkage of this system to the beamline, without use of the post-focus mirrorbox.

Functional Description

VUV Beamline 3.2 is equipped with a five metre McPherson high resolution normal incidence monochromator, which employs two diffraction gratings to provide radiation in the range 5-35eV with a best resolution of 2meV. The beamline is used principally for gas-phase atomic and molecular experiments, but can also accommodate the MoLES and HiResPES endstations.

Technical Description

The station consists of a five metre normal incidence concave grating monochromator, preceeded by two premirrors. A post-focusing mirrorbox is normally fitted to deflect the exit beam onto the experimental platform, simultaneously providing a protective differential pumping stage between the experimental chamber and the monochromator. Two interchangeable gratings cover the photon energy range 5 - 35eV (2500 - 350 Angstrom) with a best achievable resolution of 2meV (0.05 Angstrom). A peak flux of 1.4 x 10^12 photons/sec, for an SRS stored beam current of 200mA, has been measured at circa 23eV.

Development

The contaminated low energy grating has been removed for refurbishment. Replacement is scheduled for October 2004.

Proposed Development

A new post-focus mirrorbox has been proposed which will increase the linear polarisation of the beamline output (to c.95%) and facilitate operations with Surface Science end-stations (useable flux increased by>10x, delivered to a 4.0 x 1.0mm beamspot).