DETECTION OF MOLECULAR-SURFACE ADSORBATES AT THE 10(-6)-MONOLAYER LEVEL AND BELOW

Ultrathin molecular surface overlayers were deposited in an UHV chambe r and were detected using pulsed infrared laser desorption followed by resonant laser post-ionization. A single-shot detection limit in the 10(-6) monolayer range was found for aniline adsorbed on silica, a sys tem whose adsorption, laser desorption and ionization properties have been well studied. An excellent signal-to-noise ratio, as well as some simple modifications that will improve the detection efficiency sugge st ultimate detection limits in the 10(-9) to 10(-10) ML range with th is scheme.