The design and performance of an energy- and angle-resolved secondary ion mass spectrometer are described. The instrument incorporates a quadrupole mass filter mounted on a flange which can be rotated under ultrahigh vacuum conditions, allowing variation of the polar collection angle of secondary ions, while rotation of the sample crystal about an axis parallel to the primary ion beam provides azimuthal angle section. Energy analyses are performed in the 0-100 eV range using a 90°spherical electrostatic sector combined with an accelerating/decelerating lens system which provides a variable 1-15 eV bandpass. Low energy electron diffraction provides complementary information on surface and adsorbate geometry. The determination of energy and angular distributions of secondary ions ejected from an ion-bombarded Ni(001)c(2×2)-CO surface illustrates the capabilities of the system.
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