Strong orientation dependence of the scattering of fluoroform by graphite (0001)

Golibrzuch

Proc. Natl. Acad. Sci. U.S.A.

et al. 2013

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 ...

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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

Golibrzuch

Proc. Natl. Acad. Sci. U.S.A.

et al. 2013

“…Although there are a lot of studies on the steric effects of diatomic molecules on surfaces, [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][26][27][28][29][30][31][35][36][37]41 the works on polyatomic molecules are rare. 1,[17][18][19][20][21][22][23][24][25][31][32][33][38][39][40] The steric effects of a polyatomic system was first reported by Novakoshi and McClelland in the CF 3 H scattering from Ag(111) surface. 1 They determined the molecular orientation of the outgoing molecule after collisions.…”

Section: Introductionmentioning

confidence: 94%

Steric Effects in the Scattering of Oriented CH₃Cl Molecular Beam from a Graphite Surface: Weak Interaction of Physisorption

2009

We report results of a study on steric effects appearing in the scattering of an oriented CH(3)Cl molecular beam from highly oriented pyrolytic graphite (HOPG) surface at 300 K. Data presented here show that the scattered CH(3)Cl beam intensity measured at a fixed scattering angle clearly depends on the initial molecular orientation toward the HOPG surface. The scattered CH(3)Cl beam intensity for the CH(3)-end collision is larger than that for the Cl-end collision, suggesting that strong anisotropy of the interaction potential induces the molecular-orientation-dependent energy dissipation during transient trapping into the physisorption well.

Z Phys D - Atoms, Molecules and Clusters

“…This has enabled elegant molecular beam experiments, pioneered by the Bernstein [1] and Brooks [2] groups, that probe the orientation dependence of symmetric top molecules colliding with reactive atoms [i-5], photons [6], or surfaces [7]. However, orientation of polar molecules other than symmetric tops by an electric field has been considered to be quite impractical.…”

Section: Introductionmentioning

confidence: 99%

On the possibility of orienting rotationally cooled polar molecules in an electric field

Friedrich

Herschbach

1991

174

112

Abstract. It has long been thought that only symmetric top molecules (or equivalent) can be appreciably oriented in an electric field. This assessment is unduly pessimistic. In molecular beams produced by supersonic expansion, the rotational temperature can be made very low (~ 1 K). For many diatomic, linear, or asymmetric top molecules, quite substantial orientation can thereby be attained for a large fraction of the beam at accessible field strengths (~ 100 kV/cm or less). We present model calculations and an experimental design to evaluate the method by observing the fluorescence of photofragments from oriented molecules. Nomograms are provided from which the orientation can be estimated for linear molecules from the dipole moment, rotational constant, rotational temperature, and field strength.