Quantum-state specific scattering of molecules from surfaces

The Journal of Chemical Physics, 2012

We describe a method to obtain absolute vibrational excitation probabilities of molecules scattering from a surface based on measurements of the rotational state, scattering angle, and temporal distributions of the scattered molecules and apply this method to the vibrational excitation of NO scattering from Au(111). We report the absolute excitation probabilities to the v = 1 and v = 2 vibrational states, rotational excitation distributions, and final scattering angle distributions for a wide range of incidence energies and surface temperatures. In addition to demonstrating the methodology for obtaining absolute scattering probabilities, these results provide an excellent benchmark for theoretical calculations of molecule-surface scattering.

The Journal of Chemical Physics, 2014

We present a combined experimental and theoretical study of NO(v = 3 → 3, 2, 1) scattering from a Au(111) surface at incidence translational energies ranging from 0.1 to 1.2 eV. Experimentally, molecular beam-surface scattering is combined with vibrational overtone pumping and quantumstate selective detection of the recoiling molecules. Theoretically, we employ a recently developed first-principles approach, which employs an Independent Electron Surface Hopping (IESH) algorithm to model the nonadiabatic dynamics on a Newns-Anderson Hamiltonian derived from density functional theory. This approach has been successful when compared to previously reported NO/Au scattering data. The experiments presented here show that vibrational relaxation probabilities increase with incidence energy of translation. The theoretical simulations incorrectly predict high relaxation probabilities at low incidence translational energy. We show that this behavior originates from trajectories exhibiting multiple bounces at the surface, associated with deeper penetration and favored (N-down) molecular orientation, resulting in a higher average number of electronic hops and thus stronger vibrational relaxation. The experimentally observed narrow angular distributions suggest that mainly single-bounce collisions are important. Restricting the simulations by selecting only single-bounce trajectories improves agreement with experiment. The multiple bounce artifacts discovered in this work are also present in simulations employing electronic friction and even for electronically adiabatic simulations, meaning they are not a direct result of the IESH algorithm. This work demonstrates how even subtle errors in the adiabatic interaction potential, especially those that influence the interaction time of the molecule with the surface, can lead to an incorrect description of electronically nonadiabatic vibrational energy transfer in molecule-surface collisions. © 2014 AIP Publishing LLC. [http://dx.

Journal of Physics: Condensed Matter, 2004

Calculations are carried out and compared with data for the scattering of CH 4 molecules from a LiF(001) surface and for O 2 scattering from Al(111). The theory is a mixed classical-quantum formalism that includes energy and momentum transfers between the surface and projectile for translational and rotational motions as well as internal mode excitation of the projectile molecule. The translational and rotational degrees of freedom couple most strongly to multiphonon excitations of the surface and are treated with classical dynamics. Internal vibrational excitations of the molecules are treated with a semiclassical formalism with extension to arbitrary numbers of modes and arbitrary quantum numbers. Calculations show good agreement for the dependence on incident translational energy, incident beam angle and surface temperature when compared with data for energy-resolved intensity spectra and angular distributions.

Surface Science, 1985

A model is formulated and applied to the recently measured vibrational and translational accommodation of NO scattered from a Pt(lll) crystal surface. The model assumes that the initial adsorption of NO occurs via a precursor state. Experimentally observed memory of the incident energy by the scattered molecules is a result of competition between chemisorption and desorption from the precursor state.

Translational and internal degrees of freedom of a scattered beam of NO molecules from a Pt(111) single crystal surface were measured as a function of scattering angle and crystal temperature in the range 450 to 1250 K. None of the three degrees of freedom were found to fully accommodate to the crystal temperature, the translational degree being the most accommodated and the rotational degree of freedom the least. A precursor state model is suggested to account for the incomplete accommodation of translational and vibrational degrees of freedom as a function of crystal temperature and incident beam energy. The vibrational accommodation is further discussed in terms of a competition between desorption and vibrational excitation processes, thus providing valuable information on the interaction between vibrationally excited molecules and surfaces. Energy transfer into rotational degrees of freedom is qualitatively discussed.

The Journal of Physical Chemistry C, 2015

ABSTRACT During a collision of highly vibrationally excited NO with a Au(111) surface, the molecule can lose a large fraction of its vibrational energy into electronic excitation of the metal. This process violates the Born-Oppenheimer approximation and represents a major challenge to theories of molecule-surface interaction. Two ab initio approaches to this problem, one using independent electron surface hopping (IESH) and the other electronic friction, previously reported good agreement with the limited available data on multiquantum vibrational relaxation; however, at that time only experiments for NO(vi = 15) at an incidence translational energy of Ei = 0.05 eV were available. In this work, we report a comparison of recently reported experiments characterizing the multiquantum vibrational relaxation of NO on Au(111) for a wider range of incidence translational and vibrational energies to IESH and molecular dynamics with electronic friction (MDEF) calculations for these conditions. Both theories fail to explain the large amount of vibrational energy transferred from NO to the solid.

Physical Review B, 1990

Based on time-independent scattering theory, we present a systematic formulation of triatomicmolecule-crystalline-surface scattering dynamics including the vibrational states of the solid (phonons) and the vibrational and rotational states of the molecular projectile. The vibrational and rotational motions of the triatomic molecule are treated by separating out the motion of the center of mass of the molecule in a manner that is suitable for treating the surface collisions with a molecular projectile. This method can be essentially applied to a general polyatomic projectile case. From the translational invariance of the full Hamiltonian, we employ the total (projectile+phonon) momentum representation parallel to the surface to derive the properties of the total scattering wave function of the triatomic-molecule-crystalline-surface system, a representation of the simultaneous phonon and vibrational-rotational transition potential matrix, and the characteristics of the independent physical solutions for a given energy and momentum of the system. The scattering equation in differential and integral forms as well as the related Green functions are also obtained. In particular, the explicit configurational expression of the Green function of the molecule-surface system presented here, including phonons and vibrations and rotations, is quite different from those of conventional scattering theory where the collision partners are spatially localized. Several important versions of the integral expressions of the scattering and transition matrices that are useful for introducing approximation schemes are also presented. The time-reversal invariance and microscopic reversibility of the triatom-surface scattering are discussed. The equations relating the incoming and outgoing scattering wave functions, which are satisfied in the present molecule-surface system and are important in the transition-matrix scheme, are also obtained. Further, the relation between the scattering matrix elements that describes the microscopic reversibility in the present scattering system is presented. Since phonon annihilation and creation are mutually time-reversed phenomena, this relation of microscopic reversibility can be tested by experiment. From the present forrnulation, some specific theoretical schemes for simultaneous diffraction and phonon or vibrationalrotational transitions, a bound-state resonance inelastic-scattering method for phonon-mediated and rotation-mediated selective adsorption and desorption, and a method of obtaining quantal physisorption probabilities are derived in the following paper. These results are suitable for the triatomic-molecular-projectile casequite realistic compared to what has been employed so far, and at the same time capable of yielding effective ab initio calculations.

Phys. Chem. Chem. Phys., 2011

Here we extend a recently introduced state-to-state kinetic model describing single-and multi-quantum vibrational excitation of molecular beams of NO scattering from a Au(111) metal surface. We derive an analytical expression for the rate of electronically non-adiabatic vibrational energy transfer, which is then employed in the analysis of the temperature dependence of the kinetics of direct overtone and two-step sequential energy transfer mechanisms. We show that the Arrhenius surface temperature dependence for vibrational excitation probability reported in many previous studies emerges as a low temperature limit of a more general solution that describes the approach to thermal equilibrium in the limit of infinite interaction time and that the pre-exponential term of the Arrhenius expression can be used not only to distinguish between the direct overtone and sequential mechanisms, but also to deduce their relative contributions. We also apply the analytical expression for the vibrational energy transfer rates introduced in this work to the full kinetic model and obtain an excellent fit to experimental data, the results of which show how to extract numerical values of the molecule-surface coupling strength and its fundamental properties.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1993

The final dissociation of a molecule scattered by a solid surface is a result of competition between two processes, namely the ~llision-induced excitation into a repulsive state and the Penning relaxation along the scattering trajectory. The correlated collision scattering by the surface atomic rows and semichannels should display an orientational effect in the excitation-induced dissociation. This could explain the azimuthal orientational effect in the dissociation of the scattered molecules. This paper reports on the effect of resonance excitation into a repulsive state, which is a version of the Okorokov effect. The inelastic interaction was also shown to influence the excitation degree of the atoms of the dissociated molecule scattered by the surface. The population of their excited states has been calculated.

Surface Science, 1976

The quantum theory of atomic scattering from hard surfaces, previously developed, is extended to cover molecular scattering, taking into account rotational transitions. Two methods (a perturbative and a nonperturbative approach) are considered: the former is applied to Hz scattering, the latter to HD scattering from LiF. A comparison with recent experimental data gives satisfactory results when a potential well of 440 K and a corrugation amplitude of 0.17 A are assumed for the Hz -LiF interaction.