By using laser methods to prepare specific quantum states of gas-phase nitric oxide molecules, we examined the role of vibrational motion in electron transfer to a molecule from a metal surface free from the complicating influence of solvation effects. The signature of the electron transfer process is a highly efficient multiquantum vibrational relaxation event, where the nitrogen oxide loses hundreds of kilojoules per mole of energy on a subpicosecond time scale. These results cannot be explained simply on the basis of Franck-Condon factors. The large-amplitude vibrational motion associated with molecules in high vibrational states strongly modulates the energetic driving force of the electron transfer reaction. These results show the importance of molecular vibration in promoting electron transfer reactions, a class of chemistry important to molecular electronics devices, solar energy conversion, and many biological processes.

Hydrogen-bonded water clusters were formed with inert gases adsorbed to them in a strong molecular beam expansion. Upon single-photon ionization of such mixed clusters using VUV light, fragmentation of the substrate water cluster ion is markedly suppressed. Experimental evidence is presented, showing that the rapid evaporation of the inert gas from the newly formed water cluster ion efficiently removes internal energy on a time scale much faster than the usual fragmentation reactions present in pure water clusters, i.e., rates of fragmentation that are normally >109 s-1. This phenomenon is exploited to produce “unprotonated” water clusters, formally (H2O) n +. Using post source decay reflectron time-of-flight mass spectrometry, the structure of the “unprotonated” water cluster ions is experimentally determined for the first time. The structure determined, H3O+(H2O) k ·OH where the hydroxyl radical is found outside the first solvation shell of the charge, is consistent with recent ab initio calculations. This simple approach to the control of fragmentation in mass spectrometry appears to have promise in applications to other interesting polymeric samples, for example biopolymers.

Measurements of vibrational excitation and deexcitation of NO (v = 2) scattering from a Au(111) surface show that the probability of both processes increases strongly with the kinetic energy of the incident NO. These results are qualitatively consistent with a vibrational energy transfer mechanism involving electron-hole pairs but not with competing adiabatic models. The form of the energy dependence, and other features of the measurements, are not in accord with existing calculations.

1829dehydes, and carboxylic acids). The strategy involves protecting-group chemistry. Carboxylic acids have been introduced by using the chemistry in eq 3. Acknowledgment. We are indebted to Dr. Ralph G. Nuzzo and AT&T Bell Laboratories for assistance in obtaining ESCA spectra and the Office of Naval Research for financial support.Registry No. PCTFE, phenyllithium, methyllithium,. A 310 430 nm Figure 4. UV-vis spectra of PCTFE oil (0), PCTFE oil after reaction (0.5 equiv) with methyllithium (O'), PCTFE film (F), and PCTFE film after reaction (5 min) with methyllithium (F').The surface modification reaction appears to be less surface selective than the two-phase dehydrofluorination of poly(viny1idene fluoride)? it does not, however, exhibit autocatalysis and pitting. If the stoichiometry in eq 2 is assumed, the mass losses at 2-, lo-, and 20-min reaction times correlate with average reaction depths of 45,136, and 285 A, respectively. The contact angle data further suggest that the reaction is not surface selective: changes within the sampling depth (several angstroms) of this technique are occurring after an average of many tens of angstroms of material have reacted.Work in progress concerns extending this chemistry to introduce surface polar functional groups (alcohols, al- I OH References and Notes(1) For a discussion of the theory of chemistry in reduced dimensions, see: Astumian, R. D.; Schelly, Z. A. J. Am. Chem. SOC. 1984, 106, 304. (2) For a discussion of chemistry in noninteger dimensions between two and three. see: Pfeifer. P.: Avnir. D.ABSTRACT Complex formation between poly(acry1ic acid) (PAA) and poly(oxyethy1ene) (POE) was studied by following changes in the emission of dansyl-labeled PAA (Dan-PAA). Addition of POE with a molecular weight of 24000 (POE-24) to Dan-PAA produced an up to eightfold increase of fluorescence with a blue shift of the maximum. Addition of much higher molecular weight POE led to a relatively small increase of fluorescence, and the emission maximum was red-shifted, suggesting increased exposure of the dansyl label to water. This was interpreted as indicating that Dan-PAA stretched out and was in contact with POE only at widely separated regions. The model was supported by the observation that addition of POE-24 to the Dan-PAA complex with high molecular weight POE leads to emission changes similar to those seen when POE-24 is added to Dan-PAA alone. Also, displacement of Dan-PAA from POE complexes by unlabeled PAA leads first to a sharp drop but later to an increase of fluorescence, indicating that Dan-PAA is first liberated in a stretched state before contracting to its equilibrium extension. An acrylic acid copolymer with 9 mol % acrylamide forms POE complexes similar to those of PAA although polyacrylamide does not complex with POE. This suggests than an uninterrupted sequence of interacting groups is not important in the formation of PAA-POE complexes.

We have measured the trapping probability of NO(v = 0 and v = 2) on Au(1 1 1) as a function of translational energy of incidence. The range of translational and vibrational energies probed is comparable, yet the influence of the two types of motion is very different; 0.46 eV of translational energy is sufficient to completely suppress trapping, but the 0.46 eV of vibrational energy in NO(v = 2) has no measurable effect. The insensitivity of trapping probabilities to vibrational energy stands in sharp contrast to the strong sensitivity of direct activated dissociative adsorption to vibrational energy.