The Model AC-2 Photoelectron Spectrometer is designed for atmospheric pressure operation and consists of an open counter equipped with a UV source to measure ionization potential and work function of surfaces in air (without vacuum). The open counter electron detector has been used for photoelectron spectroscopy in the air (PESA). By combining the open counter with a UV source, the AC-2 PESA instrument opens the way to a new dimension in surface analysis. The AC-2 is capable of measuring large samples up to 50 mm X 50 mm, powder samples and films on a surface. Measurements can be taken is five minutes.