In this Experimental Physical Chemistry project, sponsored by the Chemistry Division, Prof. Anderson (SUNY Stonybrook) will develop a new and powerful method for preparing polyatomic ions in specific excited vibrational states. The effect of specific vibrational excitation on ion reactivity will then be studied by high resolution molecular beam methods. The primary question to be answered is, "in what range of molecular size and vibrational energy are vibrational mode effects important?" A clear answer to this question will determine the future course of research in this field for many years to come. %%% Bonds which hold molecules together are not rigid; they stretch and vibrate. A long sought goal of physical chemistry is to influence the course of chemical reactions by stimulating specific vibrations in order to facilitate breaking specific bonds. Prof. Anderson (SUNY Stonybrook) will develop a new method for doing this using simultaneous irradiation by lasers of two different wavelengths. This is important because the method can be applied to larger and more chemically relevant molecules than was previously possible.