Collision surface for improved ionisation

A mass and/or ion mobility spectrometer comprises a device arranged to generate aerosol, smoke or vapour from a target to be analysed, and a device arranged to direct the aerosol, smoke or vapour onto a collision assembly. The collision assembly may be a hollow collision assembly having an inner cross-sectional area that reduces from an inlet to an outlet of the hollow collision assembly. Aerosol, smoke or vapour may be received at the inlet to impact upon an inner surface of the hollow collision assembly to generate analyte ions that emerge from the hollow collision assembly via the outlet. Alternatively, the collision assembly may be a mesh. The collision assembly may be located within a vacuum chamber and may be heated. The aerosol, smoke or vapour may be intermixed with a matrix. Droplets of the diluted or dissolved aerosol, smoke or vapour may be accelerated onto the collision assembly by a pressure difference across an atmospheric interface.