  We present a new velocity map imaging instrument for studying molecular beam
surface scattering in a near-ambient pressure (NAP-VMI) environment. The
instrument offers the possibility to study chemical reaction dynamics and
kinetics where higher pressures are either desired or unavoidable. NAP-VMI
conditions are created by two sets of ion optics that guide ions through an
aperture and map their velocities. The aperture separates the high pressure
ionization region and maintains the necessary vacuum in the detector region.
The performance of the NAP-VMI is demonstrated with results from N$_2$O
photodissociation and N$_2$ scattering from Pd(110) surface, which are compared
under vacuum and at near-ambient pressure ($ 1\times10^{-3} $ mbar). NAP-VMI
has the potential to be a applied to, and useful for, a broader range of
experiments including photoelectron spectroscopy and scattering with liquid
microjets.

Chemical Physics