Observation of orientation-dependent electron transfer in molecule–surface collisions

Abstract

Molecules typically must point in specific relative directions to participate efficiently in energy transfer and reactions. For example, Förster energy transfer favors specific relative directions of each molecule's transition dipole [Förster T (1948) Ann Phys 2(1-2):55-75] and electron transfer between gas-phase molecules often depends on the relative orientation of orbitals [Brooks PR, et al. (2007) J Am Chem Soc 129(50):15572-15580]. Surface chemical reactions can be many orders of magnitude faster than their gas-phase analogs, a fact that underscores the importance of surfaces for catalysis. One reason surface reactions can be so fast is the labile change of oxidation state that commonly takes place upon adsorption, a process involving electron transfer between a solid metal and an approaching molecule. By transferring electrons to or from the adsorbate, the process of bond weakening and/or cleavage is initiated, chemically activating the reactant [Yoon B, et al. (2005) (111) surface with the N atom oriented toward the surface. This represents a rare opportunity to investigate the steric influences on an electron transfer reaction happening at a surface.dynamics at surfaces | orientation of molecules | rotational rainbow T he measurement of the orientation dependence of reaction rates can provide a sensitive test of theories of chemical processes. Electron transfer (ET) reactions are of particular interest in this regard, both because of the fundamental issues they pose involving subtle long-range orientation-dependent interactions, and because of the importance of ET in a remarkably wide range of phenomena. Long-range ET reactions play an important role in living systems (1). They are important in catalysis on metals and zeolites (2), in rechargeable batteries, in corrosion (3), and in photosynthesis (4).On metal surfaces, an ET reaction may proceed by transient formation of a molecular anion via excitation of electronic states of the metal, often precluding a description of the reaction mechanism within an adiabatic picture based on the BornOppenheimer approximation (5, 6). As in the analogy to whaling used in naming gas-phase ET reactions, this process of an electron jump from the surface to an approaching molecule is often referred to as "harpooning" (7). There are many studies of the orientation dependence of harpooning in gas-phase reactions (8, 9), but little is known about steric influences on ET reactions during molecule-surface scattering events. An influence of N 2 O orientation on exoelectron emission has been seen for reactions at alkali surfaces (10). Mechanistic studies revealed evidence for an Eley-Rideal reaction involving an ET event (11, 12). However, theoretical considerations suggest that the ET from the solid to N 2 O is independent of N 2 O orientation (13). To our knowledge, there is no unambiguous measurement of the orientation dependence of an ET reaction at a solid surface.We have found a unique way to measure the orientation dependence of a simple ET reaction occurring when ...

The importance of accurate adiabatic interaction potentials for the correct description of electronically nonadiabatic vibrational energy transfer: A combined experimental and theoretical study of NO(v = 3) collisions with a Au(111) surface

“…It has been shown that electron transfer is an important part of the electronically nonadiabatic dynamics in this system. 26,44 It is believed that DFT may describe electron transfer inadequately in molecular interactions at metal surfaces. 45 Hence a more fundamental, but also more elaborate, improvement would be to replace the DFT calculation by more advanced methods such as quantum mechanical embedding theory, which allows a true ab initio description of the system.…”

Dynamical steering in an electron transfer surface reaction: Oriented NO(v = 3, 0.08 < Ei < 0.89 eV) relaxation in collisions with a Au(111) surface

“…1 in Ref. 15. The average angle (expectation value <Θ>) between electric field lines (which means surface normal for the employed experimental setup geometry) and dipole moment (bond axis) is 68…”

“…15 Due to increased attraction when approaching the surface with the N-atom first, the NO molecules can approach the surface more closely than for configurations with the O-atom first. This results in more efficient electron transfer from the surface to the NO molecule-forming transient NO − -an event which is essential to the electronically nonadiabatic vibrational relaxation.…”

Electronic Friction Dominates Hydrogen Hot-Atom Relaxation on Pd(100)

“…In contrast, the relevance of this dissipation channel in gas-surface interactions that involve energies up to a few eV is not so clear. It depends not only on the specific system, but also on the elementary process considered, as shown by different studies on scattering [5][6][7][8][9][10][11][12] and adsorption [6,[13][14][15][16][17][18][19][20][21][22][23][24][25][26] of atoms and molecules on surfaces. Low-energy e-h pair excitations have been detected as chemicurrents on Schottky diode devices during the chemisorption of atomic and molecular species on metals [13][14][15].…”